Your Mesa/Boogie Amplifier is a professional instrument. Please treat it with respect and operate it properly.
USE COMMON SENSE AND ALWAYS OBSERVE THESE PRECAUTIONS:
Do not expose amplifier to moisture, rain or water, direct sunlight or extremely high temperatures. Always insure that amplifier is properly grounded. Always unplug A.C. power cord before changing fuse or any tubes When replacing fuse, use only same type and rating Avoid direct contact with heated tubes. Insure adequate air circulation around amplfier. Keep amplifier away from children. Be sure to connect to an A.C. power supply that meets the power suplly specifications listed on the rear panel of the unit. If there is any danger of lighting occurring nearby, remove the power plug from the wall socket in advance. To avoid damaging your speakers and other playback equipment, turn off the power of all related equipment before making the connections. Do not use excessive force in handling buttons, switches and controls. Remove the power plug from the A.C. mains socket if the unit is to be stored for an extended period of time. Do not use solvents such as benzene or paint thinner to clean the unit. Wipe off exterior with soft cloth. Be sure to have the warranty card for this product filled out by the store at which it was purchased and return to Mesa Engineering promptly.
YOUR AMPLIFIER IS LOUD! EXPOSURE TO HIGH SOUND VOLUMES MAY CAUSE PERMANENT HEARING DAMAGE! No user serviceable parts inside. Refer service to qualified personnel. EXPORT MODELS: Always insure that unit is wired for proper voltage. Make certain grounding conforms with local standards. READ AND FOLLOW INSTRUCTIONS OF PROPER USAGE.
DC-5 Operating Instructions

Overview:

Your DC-5 amplifier was designed to deliver maximum performance in a format based on simplicity. Its easy to dial nature allows each of the two channels to deliver a wide range of sounds in both clean and overdrive styles. The Dual Caliber uses two 6L6 power tubes to fuel its healthy fifty watt power section. We are pleased by its surprising headroom, yet truly musical clipability when pushed. The DC-5s pre-amp was no afterthought as you may have deduced by the six 12AX7s tucked snugly away under the swing away tube clamp. Two separate sets of tubes are used to accomplish the Rhythm and Lead channels. Its really like having two separate amplifiers built into one chassis. Ultimate flexibility is achieved by providing two complete sets of Tone and Master controls as well as the channel assignable 5 Band Graphic Equalizer. Two different sounds can be switched between without compromising tone or levels. Looking to the Rear Panel assures that all your interfacing needs are covered. A parallel effects loop with a Mix control provides tone insurance for even those questionable effects. A recording circuit dialed for direct to board sessions provides accurate reproduction of the DC-5s pre-amp. When the session goes late into the night, the silent recording speaker mute switch comes in real handy. To use the DC-5 in larger rack systems, or to interface to other power sections, the Slave Jack and Level Control is a welcome feature. Three speaker jacks (one 8 ohm, and two 4 ohm) are provided to ensure the proper impedance match to many types of speaker enclosures. An auto assign EQ rotary control lets you decide whether the 5-Band graphic enhances the Rhythm Channel, the Lead Channel, both, or even allows footswitching of the EQ independently. The Reverb can also be footswitched in or out. As you can see, the DC-5 provides all the features any demanding pro could need and at the same time remains simple to operate.

FRONT VIEW DC-5

RHYTHM

OUTPUT LEVEL 6600

REAR VIEW DC -5

IN OUT

LEAD FT SW

2.5A SB

EQ SELECT FTSW EQ/REV

SEND RETURN

FX MIX RECORDING SPEAKERS

MUTE SPKR ON

SILENT RECORDING

MESA BOOGIE

HANDBUILT IN PETALUMA PATENT APPLIED FOR

PAGE 1

FOOT SWITCH

TREBLE

PRESENCE

REVERB

MASTER

LEAD STANDBY POWER

DUAL CALIBER DC-5

FRONT PANEL:

First familiarize yourself with the layout of the Front Panel and locate the Lead / Rhythm switch on the right side of the chassis, next to the STANDBY Switch. This toggles you between the top (Rhythm) Channel and the bottom (Lead) Channel. If you dont have the Rhythm/Lead Footswitch connected, this switch will activate the channel switching function. Before we get too critical about each control, lets audition the two channels with a basic clean setting in the Rhythm Channel and a fairly high gain overdriven sound in the Lead Channel.

POWER-UP:

Connect your favorite guitar to the instrument input jack. FLIP the power switch ON while leaving the standby switch set to STANDBY. (Its always a good idea to practice this start up procedure) as at least 30 seconds of warm-up time lessens the shock on cold power tubes, thus prolonging their life substantially. Next set the controls and the Graphic EQ per this example:

PULL BOOST

OUTPUT LEVEL

STANDBY POWER

Flip the STANDBY Switch to the ON position and listen to the two channels using either the footswitch or the Channel Select toggle switch found on the right side of the Front Panel. The EQ Rotary Control on the left side of the Rear Panel, controls the EQ assignment. This popular V type curve works well in both Rhythm and Lead Channels, but most players tend to use it more in the Lead Channel, finding the Rhythm plenty sweet by itself without the use of the EQ. (see page 5 for more information on EQ) Again, these are merely examples of the two channels. Experimentation leads to finding many different sounds in each channel and understanding the controls and the way they interact, can make this much easier and more fun. Now lets get specific!

EQ SELECT

FTSW EQ/REV
Now that you have heard the DC-5s two channels, lets move on to understanding the controls and their interactive roles in achieving the sounds that you want to hear.

GAIN TREBLE

MIDRANGE: Through endless daily tone dreaming, the if-only design dictum led to the dial-in-gain boost. In the DC-5 a third over the top crunch sound was made possible by the inclusion of the RHYTHM Channels dual purpose MID Control. From 0 to about 3 the taper is adjusted to act as a very effective MID Control. As you increase the MID to 4 and BOOST INPUT PULL above, you will hear the lower Mids getting more pronounced and fatter. At about the MID leaves behind the old notion of being a tone control and becomes a truly usuable gain control. This upper range is a smokin addition to the RHYTHM Channels FOOT GAIN TREBLE MID GAIN Control for all kinds of higher gain rhythm sounds. Try the MID set high and the SWITCH 5 GAIN Control at about for a cool blues solo sound. Dime the MID and activate the GAIN Controls Pull Boost for a grinding crunch rhythm sound. If this still isnt crazy enough for you.Max the GAIN and TREBLE Controls and set the PRESENCE Control to 0 or 1 , turn on the Graphic and give it the old V curve and plug into a 4x12 with some Celestion Vintage 30s or 25s. This should be sufficently heinous for even the sickest crunch fiends. As you can see, the versatility that this dual purpose MID control lends to the rhythm channel greatly expands its usefulness as both a clean and overdrive channel.
NOTE: The lower region of the MID Control determines midrange punch and boldness in lower gain sounds and a smooth vocal blend in high gain sounds. It can be very effective acting as a cut through the band control in certain situations. Remember, settings of the TREBLE Control greatly affects this controls strength.

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BASS: This control blends in the lower frequencies and its effectiveness, again, depends on the setting of the TREBLE Control. It should be set with moderation as extreme settings in either low or high directions can produce an unbalanced tone. Be especially careful in higher Gain settings of either channel. Too much Bass will cause a flabby unfoBOOST INPUT PULL cused sound that cant be dialed out with the graphic EQ because excessive 6 Bass has been introduced to the pre-amp in the early stages. Try setting the BASS control to 6 for clean sounds in the RHYTHM Channel and 4 or FOOT GAIN TREBLE MID BASS below when dialing up high gain overdriven sounds in this channel. In the LEAD SWITCH 5 Channel, try setting the Bass somewhere between 3 and 6. These settings will vary with the amount of Gain and Treble you have dialed up.

PRESENCE: These two controls attenuate the high end and control dynamic compression in the power section. High settings produce more sparkle, cut and lend a more open quality to the Channel. Low settings of the PRESENCE control compress the sound and enhance the more vocal qualities of single notes.
This control can also produce a fatter, warmer character, especially in the LEAD Channel. Lower Treble settings, combined with low PresFOOT GAIN TREBLE MID BASS PRESENCE ence settings produce the richest, roundest lead sounds. Try setting SWITCH 2 the RHYTHM Channels PRESENCE Control at around 5 or 6 for for the sweet blend of sparkle and cut. This range in the RHYTHM Channel also tends to give the impression of more headroom. Try a LEAD Channel PRESENCE Control setting of 3 to start with and adjust to taste. Avoid setting the LEAD PRESENCE Control to 10 when high Gain and Treble settings are in use. This reduces the likelihood of annoying microphonic tube problems.
REVERB: The DC-5 has an individual REVERB Control per channel. This enables different amounts of the rich ALL TUBE Reverb to be mixed with the dry signal of each channel. It is normal for extreme settings of the REVERB Control to slightly alter the character of the channel as the voicing of the Reverb circuit becomes more BOOST INPUT PULL 3 dominant in the mix.
MASTER: The individual channel MASTER Controls serve three purposes in the layout of the DC-5. FIRST: They serve as level balancing controls for each of the two channels. This enables a wide range of front end gain settings to be matched to a given listening level and the level of the other channel. SECOND: They 4 act as effects send controls, for each channel, in the Effects Loop. As with many of the controls on the DC-5, the best results for balance and tone are usually found in the meBASS PRESENCE REVERB MASTER dium range of this control. THIRD: The Master Control is the Recording jacks send level 4 control.

PAGE 4

MASTER (continued)
When using the direct Recording jack found on the Rear Panel to interface directly to a mixing board or recorder, this control will determine the amount of signal you will be sending via this jack. In this application it is usually best to start with the MASTER Controls set to 0 and gradually increase them to the proper level. This minimizes the possibility of blowing speakers or eardrums in the event the engineer has an extremely sensitive input headroom setting in place at the console. NOTE: When trying to use your DC-5 at extremely low volume levels it will be necessary to reduce the far left GAIN control. Once the Masters and Output Levels has been reduced to roughly 1.5, reducing the Masters or Output Level below this point causes phase interaction that prevents a clean signal from passing through this circuit junction. If you must use your DC-5 at whisper levels to practice late at night etc.get used to reducing the Gain as well as the Masters and Output levels. This effect is most noticeable in the Rhythm channel set for a crystal clean sound. In the Lead channel set for a high gain sound the interaction effect is greatly reduced and virtually unnoticeable.

GRAPHIC EQ:

The five band graphic provides limitless additional shaping of the already curvacious tone. It is bypassable and channel assignable. It is also footswitchable manually via the stereo 1/4 inch jack located on the Rear Panel. These assignment choices are menued on the rear panel around the rotary control that is used to choose each position. The five choices are: OUT all the time (bypassed), IN all the time (engaged), IN on the Rhythm Channel, IN on the Lead Channel and Footswitchable. The Graphic is not a necessity to amazing tone, but can greatly enlarge the scope of sonic possibilities through experimentation. If you never turned it on you would still have one of the most amazing sounding amps around.but its there.so you may as well take a crack at some tweaking. One setting that keeps popping up as a classic Boogie EQ curve is the fabled V. This setting increases the bottom, scoops the mids and leaves the highs to do their harmonic best. Be sure to try this at some point as many Boogie users have found it to be their main sound with its huge wideness and spread. Below are some sample settings that we see used quite often, but by all means experiment.
The fabled "V" shape

PAGE 5

OUTPUT LEVEL:
This lonely knob is the DC-5s final Output knob or overall master. After the relative balance of the two channels has been set with the channel MASTER controls, use this OUTPUT control to increase or decrease the listening volume. It is also the effects return level control, a point we thought you should know. This design element makes setting up a lot easier and gives you one less knob to deal with when interfacing to your favorite effects. RHYTHM ON ON Optimum setting depends on the size of the room you wish to rock, but generally the DC-sounds best with a setting somewhere between 2 and 6 on the OUTPUT LEVEL control.

TOGGLE SWITCHES

RHYTHM / LEAD:
This toggle calls up one channel or the other and can take the place of the channel select footswitch when there isnt one handy.

RHYTHM ON ON

ON/STANDBY:
Perfect for set breaks. this toggle switch also serves an even more important purpose. In the STANDBY position the tubes are at idle so that during power up they may warm up before being put to use. Before Power is switched on make sure the Standby switch is in the STANDBY position. Wait at least 30 seconds and then switch the STANDBY to the ON position. This prevents tube problems and increases their toneful life substantially. RHYTHM ON ON

POWER:

This switch delivers the A.C. power to the DC-5. Make sure the unit is grounded (All three terminals of the A.C. cord must be connected whenever possible to avoid injury to the user as well as to the unit) and that the proper voltage is present. Follow the cold start procedure described in the above section ON / RHYTHM ON ON STANDBY when powering up your DC-5. 0 1

PAGE 6

REAR PANEL:
This is the A.C.s (Alternating Current) main fuse and provides electrical current protection from outside A.C. fluctuations, as well as power tube failure damage. Should the FUSE blow, replace it with the same rating in a slo-blo type package. The domestic U.S. version requires a 2.5 amp slo-blo fuse. A power tube short or failure is often the cause of a blown fuse.Follow the 1.25A cold start procedure mentioned in the ON/STANDBY switch section and watch the two 6L6 tubes as you turn the Standby switch to the ON position. If a power tube is going bad or is arcing you will see it! Flip the Standby switch to FUSE STANDBY immediately and replace the faulty power tube and the FUSE if necessary. 2.5A SB If you see nothing abnormal as you lift the STANDBY switch, it is possible that a power tube shorted temporarily and blew the FUSE. If this is the case it may work again normally. To be extra safe you may want to replace both power tubes in the shotgun troubleshooting tradition and save the replaced set as spares. NOTE: Like tires on a car, spare tubes are always a measure of good insurance. Your DC-5 was carefully constructed with reliability in mind! Given the proper care and maintenance, it will deliver years of trouble free service. However, any pro guitarist who is out there gigging will tell you; spare tubes are a must for the fabled cord bag and may someday be worth their weight in gold. Spare fuses are also a very easy way to insure an uninterrupted performance.

EQ SELECT:

As we mentioned earlier in the Graphic EQ section, this rotary control is used to select the assignment of the 5 assignment of the 5Band Equalizer. Band Equalizer. See Graphic EQ section on page 5 for an explanation of the 5 pos1.25A RHY IN LEAD sible positions of this rotary control.

FTSW EQ/REV:

This 1/4" Stereo jack allows you control of the EQ and Reverb remotely when a Stereo cable and Mesa Dual Footswitch are connected. This footswitch is an option and can be ordered by calling us direct, or by contacting your nearest MESA / Boogie Pro Center.

PAGE 8

REAR PANEL: (continued) SLAVE:
This 1/4" jack and control provide a signal derived from the speaker jack. Perfect for using the DC-5 as a master pre-amp, or additional power amps may be connected for more power when needed. Some players use this to derive an FX Send Signal and go to other amps for their wet sound.
NOTE: Once a signal is taken from the SlAVE, it can not be inserted back into the FX Loop Return jack or a feedback loop will occur. Much like holding a microphone into the PA systems cabinets.a loud high pitched squeal will occur.

SPEAKER:

One 8 ohm and two 4 ohm speaker jacks are provided. The DC-5 is not very sensitive to speaker mismatches and will not be damaged by them, except that very low ohmage loads will cause the power tubes to wear faster. A single twelve-inch 8 ohm speaker should generally be connected to the 8 ohm output. When using two 8 ohm speakers, connect them both to the 4 ohm outputs provided (because the total load is 4 ohms in that case.) 4X12 cabinets may be 4, 8 or 16 ohms; if you are not sure of the impedance of your cabinet, you may need to remove the rear panel to see what the ohmage of the individual speakers are. MESA/Boogie 4X12 cabinets come standard wired to 8 ohms. They have four 8 ohm speakers wired in series-parallel. Some Non-Mesa 4X12 cabinets are wired 16 ohms using four 16 ohm speakers. By wiring all four speakers in parallel, you can reduce the cabinet to an impedance load of 4 ohms (assuming the speakers are 16 ohms each.) No matter how unusual your speaker setup, it is always possible to get good performance. If you need two 8 ohm speaker jacks (in order to run two 16 ohm cabinets at the same time), you can use a Y-box and daisy-chain the cabinets together.

SPEAKERS

Feel free to experiment with the speaker jacks, trying different loads. Many great sounds and feels may be achieved by experimenting with different combinations of speaker impedance. Keep in mind the greatest clean headroom is always achieved with proper impedance loads.i.e. an 8 ohm speaker connected to an 8 ohm jack. NOTE: Always use a load on the DC-5 when playing, unless you are recording direct and have the silent recording switch set to the Mute position.

PAGE 9

SUGGESTED SAMPLE SETTINGS

SAMPLE 1

Sparkling Clean

CHANNEL Rhythm

GAIN TREBLE MID BASS PRESENCE REVERB MASTER

STANDBY

SAMPLE 2 Pushed Bluesy Rhythm/Solo
SAMPLE 3 Crunch Rhythm (activate pull/boost)

INPUT PULL

EQ Optional
SAMPLE 4 High Gain Lead/Crunch

CHANNEL Lead

PAGE 10

PERSONAL SETTINGS PAGE

CHANNEL

SAMPLE 2

SAMPLE 3

SAMPLE 4

PAGE 11
TUBE NOISE & MICROPHONICS You may occasionally experience some form of tube noise or microphonics. Certainly no cause for alarm, this quirky behavior comes with the territory and the Tone. Much like changing a light bulb, you dont need a technician to cure these types of minor user serviceable annoyances and in fact, youll be amazed at how easy it is to cure tube problems.by simply swapping out a pre-amp or power tube!
First may we suggest that you set the amplifier up on something so that you can get to the tubes comfortably without having to bend down. It also helps to have adequate lighting as you will need to see the tube sockets clearly to swap tubes. Use caution and common sense when touching the tubes after the amplifier has been on as they may be extremely hot! If they are hot and you dont want to wait for them to cool off, try grasping them with a rag and also note that the glass down around the bulbous silvery tip is considerably less hot which makes it easier to handle. Gently rock the tube back and forth as you pull it away from its socket.
DIAGNOSING POWER TUBE FAILURES: There are two main types of tube faults: shorts and noise. Both large and small tubes may fall prey to either of these problems but diagnosis and remedy is usually simple.
If a fuse blows, the problem is most likely a shorted power tube and shorts can either be mild or severe. In a mildly shorted tube the electron flow has overcome the control grid and excess current flows to the plate. You will usually hear the amp become distorted and begin to hum slightly. If this occurs, quickly look at the power tubes as you switch the amp to STANDBY and try to identify one as glowing red hot. It is likely that two of a pair will be glowing since the shorted tube will pull down the bias for its adjacent mates, but one tube may be glowing hotter and that one is the culprit. The other two are often fine unless theyve been glowing bright red for several minutes. Because there is no physical short inside the tube (just electrons rioting out of control) merely switching to STANDBY for a few moments then back to ON will usually cure the problem.at least temporarily. Watch the tubes carefully now. Should the problem recur, the intermittent tube will visibly start to over heat before the others and thus it can be identified. It should be replaced with one from the same color batch, shown on its label. Call us and we will send one out to you. The severe short is not nearly so benign. In the worst cases, a major arcing short occurs between the plate and the cathode with visible lightning inside the glass and a major noise through the speaker. If this is seen to happen, IMMEDIATELY turn the amp to STANDBY. By this time the fuse probably will have blown. Such a short is usually caused by a physical breakdown inside the tube including contaminate coming loose or physical contact (or near contact) between the elements. Replace it and the fuse with the proper slo-blo type and power up the amp using the power up procedure as we described earlier in this manual.

TUBE NOISE: Often caused by contamination within in a tube, the culprit can usually be identified, and by lightly tapping on the glass, you will probably hear the noise change. Hearing some noise through the speakers while tapping on the 12AX7s is normal however. And the one nearer the INPUT will always sound louder because its output is being further amplified by the second 12AX7.
The power tubes should be all but quiet when they are tapped. If crackling or hissing changes with the tapping, you have probably found the problem. To confirm a noisy power tube, merely put the DC-5 on Standby, remove it from its socket and turn it back on. It will cause no damage to run the DC-5 briefly with one power tube missing. You may notice a slight background hum, however, as the push-pull becomes unbalanced. Whenever you are trying to diagnose a suspect tube, keep your other hand on the POWER and STANDBY switches ready to shut them off instantly in the unlikely case you provoke a major short. If you think youve located a problem tube but arent sure, we recommend substituting the suspect with a new one just to be sure of your diagnoses. You will be doing yourself and us a big favor by just following the simple guidelines previously mentioned regarding tube replacement. Youll probably be successful with much less effort than is required to disconnect everything and haul the unit to a technician who will basically perform the same simple tests. If the tubes are still within their six-month warranty period, we will happily send you a replacement. Just note the color designation on the tube label so that we can send you the appropriate match.

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DIAGNOSING PRE-AMP TUBE PROBLEMS: Because your amplifier is an all tube design, it is quite possible that you will at some point experience minor pre-amp tube noise. Rest assured - this is no cause for alarm and you can take care of the problem yourself in a matter of minutes by simply swapping tubes.
Let us begin by saying; It is a very good idea to keep at least a couple of spare pre-amp tubes on hand at all times to insure uninterrupted performance. These minor pre-amp tube problems can take many forms but can generally be described in two categories: Noise and Microphonics. Noise can be in the form of crackling, sputtering, white noise/hiss and/or hum. Microphonic problems usually appear in the form of a ringing or high pitched squealing that gets worse as the gain or volume is increased thus are more noticeable in the higher gain HI modes. Microphonic problems are easily identified because the problem is still present even with the instruments volume off or unplugged altogether - unlike pick-up feedback which ceases as the instrument is turned down. Microphonic noise is caused by mechanical vibration and shock: think of banging a microphone around and youll understand where the word came from. The best way to approach a pre-amp tube problem is to see if it occurs only in one specific mode or channel. Then all that remains is to swap the suspect tube for a known good performer. If you cannot narrow down the trouble to a specific mode or channel, the problem may be the small tube that drives the power tubes which is operational in all modes and channels. Though rare, a problem with the driver tube would show up in all aspects of performance - so if you cant narrow the problem down to being mode or channel specific, you may want to try replacing the driver tube. Driver problems generally show themselves in the form of crackling or hum in all modes of performance and/or weak overall output from the amplifier. Occasionally an anemic driver tube will cause the amplifier to sound flat and lifeless, but this is somewhat uncommon, as worn power tubes are a more likely suspect for this type of problem. Sometimes making the diagnosis is more trouble than its worth and its faster and easier to merely replace the small pre-amp tubes ONE AT A TIME with a replacement known to be good. But MAKE SURE you keep returning the tubes to their original socket until you hit the one that cures the problem. Youll notice that tubes located nearer to the INPUT jack always sound noisier.but this is because they are at the start of the chain and their noise gets amplified over and over by the tubes that follow. The tube that goes into this input socket (usually labeled V1) needs to be the least noisy of the bunch. The tube that goes at the end of the preamp chain - just ahead of the power tubes - can be quite noisy without causing any problem at all. The tubes in your amp have already been located in the most appropriate sockets and this is why you should NEVER pull them all out at once and ALWAYS swap them one at a time. ALWAYS return a perfectly good tube to its original socket. Also its a good idea to put the amp on STANDBY when swapping tubes to reduce the heat build up in the tubes themselves and to prevent explosive noises (which can still occur even if you are pulling the tubes away from their sockets gently) from coming through the speaker. Remember, take your time, be patient and chances are real good that you can fix your amp yourself by finding and replacing the bad tube. It kills us to see someone who has shipped their amp back to us.and all it needed was a simple tube replacement! If you must send back your amp, unplug the power cord, speaker and reverb cables then remove the chassis from the cabinet by unscrewing the four mounting bolts on top. The chassis then slides back like a drawer and comes out. Remove the big power tubes and mark them according to their location from left to right 1, 2 etc. They need to be wrapped separately with plenty of wadded up newspaper around them and put in a smaller box within the larger carton. To wrap the chassis, use plenty of tightly wadded up newspaper so there is at least six inches of crush space between the chassis and the cardboard box. Bubble wrap also works well, but please DONT use styrene peanuts - they will shift during transit and get lodged inside your electronics as well as allowing your amp to end up at the bottom of the box unprotected and possibly damaged. Pre-amp tubes dont normally wear out as a rule. Therefore, it is not a good idea to change them just for the sake of changing them. If there isnt a problem - dont fix it. If there is no result from your substitutions, it may be possible that you have more than one problematic tube. Though rare, this does happen and though it makes the troubleshooting process a little more intimidating, it is still possible to cure the problem yourself. NOTE: It is normal to hear a slight metallic ringing sound when tapping on the preamp tubes. As long as the tube does not break into oscillation or start crackling or any other form of bizzare noise, it is considered normal and functional.

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BIAS ADJUSTMENT: (Part of a continuing series)
NOTE: An article written by Randall Smith that we thought you might find interesting. Heres a question we often hear: Why doesnt Mesa put bias adjustments in their amplifiers? Well, theres a short answer and a long answer to this question.
CATHODE ( ) GRID ( , ) SCREEN GRID ( )
BEAMCONFINING ELECTRODE ( )

PLATE ( , )

The short answer is that during my 12 years of repairing Fenders, one of the most frequent problems I saw was bias controls that were either set wrong or that had wandered out of adjustment due to vibration. As any honest tech will tell you, theres lots of easy money to be made by sprinkling holy water on amplifiers. uh, what I meant to say is Your amp needed biasing. See what I mean? What customer is going to argue with that? It only takes a moment and a volt meter: The Fender diagram shows how: Adjust this trim pot for - 52 volts. Thats it. Nothing more. Now dont be fooled into thinking that tubes draw more or less bias, they dont. The way a bias supply is connected to a tube is akin to a dead end road, it just trails off to nowhere without really completing a circuit. Its a static voltage and regardless of what tube is in the socket or even if the tubes arent plugged in at all, it doesnt change the bias voltage a bit. So the end of the short answer is this: Since a bias supply needs to put out the right voltage and never vary, I wanted to build amplifiers that were individually hard wired to the correct values and NEVER needed adjustment. And for 25 years, thats how Mesa/ Boogies have been built. Time to change tubes? Just plug our tubes into any one of our amps and youre DONE. No tech needed. NO bills and no BS about biasing. And most important: The bias is RIGHT because it cant change! Now, you want the long answer? Heres more information on how our hard-wired bias avoids trouble. Please read on. But first, lets make an important distinction. Our business is designing and building high performance amplifiers. And for this we need tubes whose variance is within a narrow range. Our warehouse is full of rejects.oh, they work they just dont perform within our tolerance range. We have a very sophisticated computer - based tube testing system (nicknamed Robotube) that matches and measures tubes over seven important parameters. It can even predict which tubes are likely to have a shortened lifetime even though they work perfectly during the test. Because our business is building quality amps, we can afford to reject a lot of wayward tubes. The guys you hear complaining because Boogies dont have bias adjusters are primarily in the business of selling tubes - not amps. They dont want to throw away 30 percent of their inventory, so they promote the idea that tubes outside our parameters can be used to customize amplifiers and they criticize us because our amps cant be adjusted to accommodate their out-of-Mesa tolerance tubes. Now you might be thinking, But I thought you just said that tubes dont draw bias, therefore they dont effect the bias supply and thus it doesnt need to be adjustable. And thats right. Tubes dont effect the bias setting, but how it effects the tubes is difficult to measure. When you set the bias (whether its by selecting the right resistors, as we do, or adjusting a trimmer which is quicker) what you are doing is establishing the correct amount of idle CURRENT that flows through the power tubes. But you cant adjust the current directly, you can only change it by adjusting the amount of bias VOLTAGE that goes onto the tubes control grids.

Structure of a 6L6 / 5881 Beam Power Pentode.

PAGE 14

BIAS ADJUSTMENT (Continued)
Voltage and current are NOT the same. Current is the AMOUNT of electricity, the quantity and is measured in amperes. Voltage is the degree of electric charge like the pressure to use the old water analogy. Let me illustrate how different voltage and current are: When you scrape your feet across a carpetted floor in dry, wintery conditions, your body can become charged with 50,000 to 100,000 volts of static electricity. And when you reach for the door knob, a spark jumps and you feel it! The voltage is super high but the current (measured in micro-amps) is tiny - otherwise you would die from electrocution. Contrast this with your car battery, which puts out a mere 12 volts. You can lay your hands right across the terminals and not feel a thing. Yet the amount of current available can run to several hundred amperes. enough to turn over a cold engine and get it started. So current and voltage are two totally separate electrical parameters though when you multiply them together, you get POWER, which is measured in watts. When you set the bias of an amplifier, you are adjusting the static VOLTAGE at the control grid of the tube in order to produce a desired amount of idle CURRENT flowing to the tubes plate. A small change in grid voltage, produces a large change in the amount of current flowing and thats basically how a tube works. Say that again because its super important: A small change in voltage at the grid causes a large change in current flowing to the plate. See, thats the essence of amplification: A small change causing a large change. And here its a small voltage change causing a large current change. The bias conditions are what determines how much current flows through the big power tubes when youre not playing. And what drives your speakers is flucuations in that current flow when are ARE playing. If the amount of current increases and decreases 440 times per second, then youll hear an A note. If the fluctions in current flow are large and still at 440 per second, youll hear an A that is LOUD! But for purposes of biasing, its the amount of plate current flowing with no signal applied thats important. Unfortunately current is hard to measure because the circuit must be interuppted as in cut the wire and the meter spliced in series with the broken circuit. But measuring VOLTAGE is easy. It is not necessary to interrupt the circuit because a voltage reading can be taken in PARALLEL with the circuit intact. Thus, as a matter of convenience, most bias settings are given in volts at the grid. even though current through the plate is the important factor. In fact plate current is so inconvenient (and dangerous) to measure that Fender doesnt even state what the correct value should be. They only give the grid voltage that will produce that current. (Thats the minus 52.) But that only happens if the tubes being used are in spec. As long as the tubes ARE in spec, the right bias voltage will always give the correct plate CURRENT but then theres no need for the bias voltage to be adjustable! If the tubes are NOT in spec, then the only proper way to re-set the bias is to cut the circuit and measure the current while adjusting the bias. but no manufacturer I know even STATES the desired current value! Be that as it may, when the original bias voltage is altered far enough, it will compensate for the tubes abnormal performance and the correct amount of idle current flow may then be restored. Clearly this is something most repair techs should not attempt. Some newer amps have LED indicators connected to the circuit which will turn on when the right threshold of current flow has been reached. This is an improvement, and almost worthy if youre willing to except resistors and lights added into your amplifiers audio path which we arent. The other advantage of this system is that it allows some amp manufacturers to avoid matching their power tubes. The thinking is that adjusting the bias to each tube separately eradicates the inherent differences between the tubes by insuring that the same current flows through each one. Again, this has some merit. but its still not as good as using tubes that are matched in the first place because compensating for the mis-match causes the push-pull circuit itself to become unbalanced. Two wrongs dont really make a right.

PAGE 15

Some of the other recommended biasing, methods such as -. tubes running red hot, increase the bias. sounds harsh and runs too cool, turn it down. are guesswork at best. Luckily, one of the great things about tube amps is that they can usually stand some abuse without causing any real harm. at least not immediately. But dont these alterations imply that you are second-guessing the amp designer and that theres a better set of operating conditions that the designer missed but the tube sellers have discovered? Now some players may like the sound of their amp altered by tubes with extreme characteristics and with the bias set to help compensate. But often it is the mere novelty of change that theyre really responding to and when the amp goes back to the proper original way, weve seen them be far happier still! Because every part in every one of our designs has been meticulously evaluated, compared and stressed over no matter how seemingly insignificant it might be. And with every design we look for a sweet spot where all the parameters including the bias come together to give the best sonic performance, consistently and reliably. Every part and voltage is important yet no one complains that these other parameters arent available for tinkering. Consider our patented Simul-Class circuitry where there are two different bias voltages used for separate pairs of power tubes. and changing one voltage also changes the other. Great care goes into getting this just right and we think wed be asking for trouble to have it adjustable for the world to play with. unless you like paying to have your amp messed up. Sorry, I meant to say, Uh,. your amp needed biasing. If that doesnt appeal to you, then merely plug a matched set of Mesa tubes into one of our amps and youre ready for tone. Guaranteed. Youd be amazed at the number of service calls we field every day that lead to a diagnosis of out-of-tolerance, non-spec tube problems. To think these would be prevented by including a bias adjustment is something of an insult to you and us. If you put the wrong size tires on your car, do you think changing the pressure will make them right? Please, dont think this is a blanket indictment of the other guys selling tubes it isnt. And their tubes arent all bad either. It just doesnt make sense to pay more of your hard earned cash for tubes that were probably made in the same Russian or Chinese factory and which have the possibility of being outside the performance window we select for your amp. And it pains us to hear the hype and mystique built up around biasing when twenty-five years of evidence affirms our decision to make bias circuits that never need adjustment. How much money and trouble that has saved Mesa/Boogie players you couldnt estimate. Our rigorously tested and hand selected tubes are available at your nearest Mesa/Boogie Pro Center or from us directly. Nobody offers better price, quality or warranty than we do. so why swerve? Next time well talk about our part in developing the great Sylvania STR 415 type and how were on the verge of seeing something fairly close reappear on the market. Remember, we still have some of these super rugged mondo-bottles available for older amps Boogies only please! Until then, Relax, Breathe and Nourish your soul! Cheers! Mesa/Boogie Ltd.

Randall Smith Designer & President

PAGE 16

DC 5 Front View
JACK pt# 610120 LED LIGHT pt# 395631 KNOB pt# (all knobs) 409108 EQ pt# 588535 EQ SLIDER KNOB pt# 408535
SWITCH pt# (all 3) 601073

POT pt# 591842

POT pt# 592148

POT pt# 592737

POT pt# 592151

POT pt# 591047

POT pt# 592738

POT pt# 592739

PILOT LIGHT pt# 703047 PILOT LIGHT LENS pt# 703784 PILOT LIGHT HOLDER pt# 703900
LED LIGHT pt# 395620 JACK pt# 610120

KNOB pt# 409115

DC5 Rear View
FUSE HOLDER pt# 790342 FUSE pt# 790250 KNOB pt# 408004 ROTARY SWITCH pt# 608102 JACK pt# 618102
KNOB pt# 408004 JACK pt# 618100 POT pt# 592737
KNOB pt# 408004 POT pt# 592737

JACK pt# 618103

JACK pt# 618100 JACK pt# 618100

SWITCH pt# 600115

ALL SPEAKER JACKS pt# 618100

PAGE 17

Thank you
for trusting MESA/Boogie to be your amplifier company and we wish you many years of toneful enjoyment from this handbuilt all tube instrument.
(707) 778-6565 FAX NO. (707) 765-Ross Street Petaluma, CA 94954 USA

MESA BOOGIE

DUAL CALIBER DC -10
The Spirit of Art in Technology
1317 Ross Street Petaluma, CA 94954
Hello from the Tone Farm.
You, smart player and all around intuitive human, have put your trust in us to be your amplifier company. This is something we do not take lightly. Our reward is that weve designed and built another fine guitar amplifier that is destined to become a classic. By purchasing and choosing this unit to be a part of your musical voice, you have become part of the Mesa family.WELCOME! Our goal is to never let you down. Your reward is that you are now the owner of a great amp, bred of fine all tube amp heritage.benefiting from the many pioneering and patented Mesa circuits that led to the refinement of your new instrument. Feel confident, as we do, this amp will inspire many hours of musical satisfaction and lasting enjoyment. It was built with you in mind, by players who know the value of a fine musical instrument and the commitment it takes to make great music. The same commitment to quality, value and support we make to you.our new friend.
Your MESA/Boogie Amplifer is a professional instrument. Please treat it with respect and operate it properly.
USE COMMON SENSE AND ALWAYS OBSERVE THESE PRECAUTIONS:
Do not expose amplifier to moisture, rain or water, direct sunlight or extremely high temperaturres. Always insure that amplifier is properly grounded. Always unplug AC power cord before changing fuse or any tubes. Avoid direct contact with heated tubes. Insure adequate air circulation behind amplifier. Keep amplifier away from children. Besure to connect to an AC power supply that meets the power supply specifications listed on the rear panel of the unit. If there is any danger of lightning occurring nearby, remove the power plug from the wall socket in advance. To avoid damaging your speakers and other playback equipment, turn off the power of all related equipment before making the connections. Do not use excessive force in handling control buttons, switches and controls. Remove the power plug from the AC mains socket if the unit is to be stored for an extended period of time.
YOUR AMPLIFIER IS LOUD! EXPOSURE TO HIGH SOUND VOLUMES MAY CAUSE PERMANENT HEARING DAMAGE! No user serviceable parts inside. Refer service to qualified personnel. Always unplug AC POWER BEFORE REMOVING CHASSIS. EXPORT MODELS: Always insure that the unit is wired for the proper voltage. Make certain grounding conforms with local standards. READ AND FOLLOW ALL INSTRUCTIONS OF PROPER USAGE.
Precautions __________________________________________________________________________ 0 FRONT PANEL: Description & Usage_____________________________________________________ Gain ________________________________________________________________________________ Treble _______________________________________________________________________________ Mid _________________________________________________________________________________ Bass ________________________________________________________________________________ Presence ____________________________________________________________________________ Reverb ______________________________________________________________________________ Master ______________________________________________________________________________ Graphic EQ __________________________________________________________________________ Mode Select __________________________________________________________________________ Level Control _________________________________________________________________________ Toggle Switches: 100 / 60 WATT: ON / STANDBY: A.C. POWER: _____________________________ 5 6

BACK PANEL: Description & Usage A.C. Receptacle_______________________________________________________________________ 7 Fuse ________________________________________________________________________________ 7 Headphone Out _______________________________________________________________________ 7 EQ Assign ___________________________________________________________________________ 8 Recording ___________________________________________________________________________ 8 FX Loop: Send & Return _______________________________________________________________ 8 FX Mix ______________________________________________________________________________ 8 Reverb & Footswitch __________________________________________________________________ 9 Silent Recording ______________________________________________________________________ 9 Slave Out ____________________________________________________________________________ 9 Speakers ____________________________________________________________________________ 9 Factory Sample Settings ______________________________________________________________ 10 Personal Settings Page _______________________________________________________________ 11 Tube Task Chart _____________________________________________________________________ 12 Tube Noise & Microphonics ___________________________________________________________ 13 Diagnosing Power Tube Failure ____________________________________________________ 13 & 14 Diagnosing Pre-Amp Tube Problems ____________________________________________________ 15 Bias Adjustment ____________________________________________________________ 16 & 17 & 18 Parts Sheet _________________________________________________________________________ 19
DC-10 Operating Instructions

Overview:

Your DC-10 amplifier was designed to deliver maximum performance in a format based on simplicity. Its easy to
dial nature allows each of the two channels to deliver a wide range of sounds in both clean and overdrive styles. This Dual Caliber uses four 6L6 power tubes to fuel its healthy one hundred watt power section. We are pleased by its surprising headroom, yet truly musical clipability when pushed. The DC-10s pre-amp was no afterthought as you may have deduced by the six 12AX7s tucked snugly away under the swing away tube clamp. Two separate sets of tubes are used to accomplish the RHYTHM and LEAD channels. Its really like having two separate amplifiers that can produce 4 different switchable sounds built into one chassis. Ultimate flexibility is achieved by providing two complete sets of Tone and Master controls as well as the channel assignable 5 BAND GRAPHIC EQUALIZER. Looking to the rear panel assures that all your interfacing needs are covered. A Parallel EFFECTS LOOP with a MIX control provides tone insurance for even those questionable effects. A RECORDING circuit dialed for direct to board sessions provides accurate reproduction of the DC-10s pre-amp. When the session goes late into the night, the SILENT RECORDING MUTE switch comes in real handy. To use the DC-10 in larger rack systems, or to interface to other power sections, the SLAVE jack and LEVEL control are welcome features. Three combinations of speaker jacks (one 16 ohm, two 8 ohm and two 4 ohm) are provided for proper impedance matches to the many different types and makes (brands) of speaker enclosures. The mini-toggle switch located next to the fuse on the rear pane l, enables you to decide whether the 5 BAND GRAPHIC EQ enhances the RHYTHM & LEAD channel, the LEAD channel only, or an assignable position that can be remotely controlled via the footswitch. The REVERB can also be footswitched in or out. As you can see, the DC-10 provides all the features any demanding pro could need and at the same time remains simple to operate.

FRONT VIEW DC-10

100 WATTS ON ON

RHYTHM

FT.SW.

LEAD + EQ

80Hz 2200 6600

REAR VIEW DC -10

FUSE RHYTHM & LEAD EQ FTSW ASSIGN

0% 10 0%

3 A SB

HEADPHONES

LEAD ONLY RECORDING

SEND REV FTSW

FX MIX RETURN

120 V. 3 A. 60 HZ.

AC POWER

MUTE SPKR ON

SILENT RECORDING

16 OHM

PAGE 1

FOOT SWITCH

TREBLE

PRESENCE

REVERB

MASTER

987 987

60 WATTS STANDBY POWER

DUAL CALIBER DC-10

SPEAKERS

FRONT PANEL:

100 WATTS

First familiarize yourself with the layout of the front panel and locate the RHYTHM / LEAD + EQ switch on the right side of the chassis, between the 5 Band Graphic EQ and MASTER LEVEL control. This toggles you between the top (RHYTHM) channel and the bottom (LEAD) channel. If you dont have the RHYTHM / LEAD + EQ Footswitch connected, this switch will activate the channel switching function. Before we get critical about each control, lets audition the two channels with a basic clean setting in the RHYTHM channel and a fairly high gain overdriven sound in the LEAD channel. POWER-UP: Connect your guitar to the Instrument INPUT jack. Flip the POWER switch ON while leaving the STANDBY switch set to STANDBY. (Its always a good idea to practice this start up procedure as at least 30 seconds of warm-up time lessens the shock on cold power tubes, thus prolonging their toneful life substantially.) Next set the controls and the Graphic EQ as shown above: Flip the STANDBY switch to the ON position and listen to the two channels using either the footswitch or the Channel Select toggle switch found on the right side of the front panel. The EQ Footswitch Assign located on the left side of the rear panel (next to the fuse), controls the EQ assignment. This popular V type curve works well in both RHYTHM and LEAD channels, but most players tend to use it more in the LEAD channel, finding the RHYTHM plenty sweet by itself - without the use of the EQ. (see page 5 for more information on EQ)

RHYTHM & LEAD

EQ FT.SW.

ASSIGN

LEAD ONLY

RECORDING

Again, these are merely examples of the two channels. Experimentation leads to finding many different sounds in each channel and understanding the controls and the way they interact, can make this much easier and more fun. Now that you have heard the DC-10s two channels, lets move on to understanding the controls and their interactive roles in achieving the sounds that you want to hear.

CONTROLS:

GAIN: This is by far the most powerful control in each channel. It not only determines the overall gain amount, shape and sensitivity of the channel.but it is also a powerful Tone control. Generally speaking, whatever is dialed here ultimately determines the channels personality. Set low, it allows cleaner, brighter sounds with enhanced dynamic response, especially in the higher frequencies. Set high the whole personality of the channel becomes darker, fatter and more overdriven.
In the DC-10 we worked hard to make sure the entire range of GAIN available is usable and more importantly, musical. Dont think for a moment that this simple one knob layout limits you as to the amount FOOT GAIN and texture of GAIN. Long neurotic hours were spent to ensure the ranges of GAIN were stylistically SWITCH 4 accurate. Its probably a good time to mention that most of the great sounds can be found by setting the GAIN control moderately, especially in the LEAD channel. For example, somewhere between 2 thru 6. In the RHYTHM channel try setting this control somewhere between 3 thru 8. Use of moderation here will reduce the likelihood of pesky microphonic tube problems ever occurring, while at the same time making the two channels easier to balance in relative listening volume and effects send signal strength.

PAGE 2

CONTROLS: (Continued)
TREBLE: As with most guitar amplifiers, the TREBLE control is the strongest of the three rotary tone controls. It adjusts the blend of high frequencies in a wide band between the midrange and presence frequency ranges. Its setting on the DC-10 also determines the blend and strength of the MIDDLE and BASS controls. Set high, it is the dominant control, minimizing the amount of MID and BASS that would be possible in the mix. Set low, the TREBLE becomes the recessive control and a warmer, darker blend is produced. Dial with care. Subtle tweaking of this control tends to INPUT 5 produce the best results.

GAIN TREBLE

MIDRANGE Your new Dual Caliber uses a unique MIDRANGE circuit that not only blends in rich warm MIDRANGE, but goes beyond to give you an added bonus. Through endless daily tone dreaming, the if-only design dictum led to the dial-in-gain boost MIDDLE control. In the DC-10 a third over the top crunch sound was made possible by the inclusion of the RHYTHM channels dual purpose MID control.
From 0 to about 3 the taper is adjusted to act as a very effective MID control. As you increase the MID to 4 and above, you will hear the lower MIDS getting more pronounced and fatter. At about 6 the MID leaves behind the old notion of being a tone control and becomes a truly usable gain control. This upper range is a smokin GAIN TREBLE MID FOOT addition to the RHYTHM channels GAIN control for all kinds of higher gain rhythm SWITCH 5 sounds. Try the MID set high and the GAIN control at about for a cool blues solo sound. If this still isnt crazy enough for you.Max the GAIN and TREBLE controls and set the PRESENCE control to 0 or 1 , turn on the Graphic and give it the old V curve. Then plug the DC-10 into a 4x12 with some Celestion Vintage 30s or 25s. This should be sufficiently heinous for even the most serious crunch fiends. The versatility that this dual purpose MID control lends to the RHYTHM channel greatly expands its usefulness as both a clean and overdrive channel.

GAIN TREBLE MID

MASTER: The individual channel MASTER controls serve three purposes in the layout of the DC-10. FIRST: They serve as level balancing controls for each of the two channels. This enables a wide range of front end gain settings to be matched to a given listening level and the level of the other channel.
SECOND: They act as Effects Send controls, for each channel, in the EFFECTS LOOP. As with many of the controls on the DC-10, the best results for balance and tone are usually found in the medium range.
THIRD: The MASTER control is the RECORDING jacks Send Level control. When using the direct RECORDING jack found on the rear panel to interface directly to a mixing board or recorder, this control will determine the amount of signal you will be sending via this jack. In this application it is usually best to start with the MASTER controls set to 0 and gradually increase them to the proper level. This minimizes the possibility of blowing speakers or eardrums in the event the engineer has an extremely sensitive input headroom setting in place at the console. NOTE: When trying to use your DC-10 at extremely low volume levels it will be necessary to reduce the far left GAIN control. Once the MASTERS and output LEVEL have been reduced to roughly 1.5 , reducing the MASTERS or output LEVEL below this point causes phase interaction that prevents a clean signal from passing through this circuit junction. If you must use your DC-10 at whisper levels to practice late at night etc.get used to reducing the GAIN as well as the MASTERS and output LEVELS. This effect is most noticeable in the RHYTHM channel set for a crystal clean sound. In the LEAD channel set for a high gain sound the interaction effect is less noticeable.

PAGE 4

The 5- BAND GRAPHIC EQ provides limitless additional shaping of the already curvaceous tone. It is bypassable and channel assignable. These assignment choices are menued on the rear panel around the mini-toggle switch (located next to the fuse. The three choices are: RHYTHM & LEAD - LEAD ONLY - and EQ FOOTSWITCHABLE / ASSIGN. The GRAPHIC is not a necessity to amazing tone, but can greatly enlarge the scope of sonic possibilities. If you never turned it on you would still have one of the most amazing sounding amps around.but its there.so you may as well take a crack at some tweaking. One setting that keeps popping up as a classic Boogie EQ curve is the fabled V. This setting increases the bottom, scoops the mids and leaves the highs to do their harmonic best. Be sure to try this at some point as many Boogie users have found it to be their main sound due to its wideness and spread. Below are some other sample settings that we see used quite often, but by all means experiment.

GRAPHIC EQ:

MODE SELECT:
This three position toggle switch located on the front panel lets you access the DC-10s three different mode choices when you do not have the Footswitch connected or there isnt one available. The choices are RHYTHM (up), LEAD (center) and LEAD+EQ (down). To use the CHANNEL SELECT FOOTSWITCH - make sure the MODE SELECT toggle is in the center (LEAD) position.

PAGE 5

LEVEL CONTROL: This lonely knob is the DC-10s final output knob or overall master. After the relative balance of the two channels has been set with the channel MASTER controls, use the LEVEL control to increase or decrease the listening volume. It is also the Effects Return Level control, a point we thought you should know. This design element makes processor interfacing a lot easier and gives you one less knob to deal ON 100 WATTS RHYTHM with when you want to adjust your overall playing volume in performance situations. 10 Optimum setting depends on the size of the room you wish to rock, but generally the DC-10 sounds best with a setting somewhere between 2 and 6 on the output LEVEL control. 60 WATTS STAND LEAD + EQ LEVEL
FRONT PANEL: TOGGLE SWITCHES
POWER: 60 / 100 WATT: The DC-10 may be used in a 100 WATT (Full Power) configuration or can be switched down to a 60 WATT (Half Power) harness for smaller venues, added power clipping possibilities or, simply for different sonic characteristics. The 100 WATT position sounds fuller and richer with more defined bass response.
The 60 WATT position leans towards a more bubbly, brighter sound that can be pushed more easily for power clip overdrive. The 60 WATT position shuts down the two center power tubes, keeping them in stand-by mode for instant power increases and may be switched while the DC-10 is in operation. If you prefer the sound of the 60 WATTposition you may feel free to use it all the time with no penalty. You may then swap the two center 6L6s for the outer pair in WATTS 12 months or so, in order to prolong the re-tubing intervals. In the unlikely event you should ever have a power tube DUAL failure, you may pull the faulty tube(s) and run the DC-10 with only the outside pair until you can replace the faulty tube(s). If you ever have to resort to this procedure, be aware that you will notice a slight hum, but dont worry.it wont hurt your amplifier at all and will cease when you have replaced the center pair with two good tubes. NOTE: To obtain the maximum headroom for clean sounds when using the DC-10 in the 60 WATT position, it is recommended that you remove the speaker cable from the 16 ohm jack and connect it to the 8 ohm jack. This is not mandatory, but will insure the best impedance match giving you the maximum power. If you prefer the sound of the 16 ohm jack or wish to clip the DC-10 at reduced volume levels.by all means leave the speakers connected to the 16 ohm output.

ON / STANDBY: Perfect for set breaks.this toggle switch also serves an even more important purpose. In the STANDBY position the tubes are at idle so that during power up they may warm up before being put to use.
Before POWER is switched ON, make sure the STANDBY switch is in the STANDBY position. Wait at least 30 seconds and then switch the STANDBY to the ON position. This prevents tube problems and increases their toneful life substantially.

STANDBY

CALIBER

A.C. POWER:

DUAL CALIBER
This switch delivers the A.C. POWER to the DC-10. Make sure the unit is grounded (All three terminals of the A.C. cord should be connected whenever possible) and that the proper voltage is present. Follow the cold start procedure as described in the ON / STANDBY section above when powering up. The total power consumption for the DC-10 is 3 Amps @ 117 Volts. Thus, a 15 Amp circuit (which is what most house circuitry is wired with) is adequate. Make sure the Euro style A.C. POWER cord is firmly seated in the power receptacle before powering up the unit.

PAGE 6

REAR PANEL:
WARNING: Unplug power before replacing fuse or removing bolts mounting chassis.
RHYTHM & LEAD EQ FTSW ASSIGN
A.C.RECEPTACLE: This Euro style A.C. power connection is perfect for quick set-ups and break-downs after the gig. Always be sure that the A.C. power cord is firmly seated in the RECEPTACLE. If you should loose the A.C. power cord that comes with your new DC-10, just give us a call and well be happy to send you another one for a nominal charge or see your local Mesa/Boogie Pro Center. WARNING:
Unplug power before replacing fuse or removing bolts mounting chassis.
FUSE: This is the A.C.s (Alternating Current) main FUSE and provides electrical current protection from outside A.C. fluctuations,
as well as power tube failure damage. Should the FUSE blow, replace it with the same rating in a Slo-Blo type package. The domestic U.S. version requires a 3 Amp Slo-Blo FUSE. A power tube short or failure is WARNING: often the cause of a blown FUSE.Follow the cold start procedure mentioned in the ON/ Unplug power before replacing FUSE STANDBY section and watch the four 6L6 power tubes as you turn the STANDBY to the fuse or removing bolts mounting ON position. If a power tube is going bad or is arcing you will see it! Flip the STANDBY chassis. 3 A SB switch to STANDBY immediately and replace the faulty power tube and the FUSE if necHEADPHONES essary. If you see nothing abnormal as you lift the STANDBY, it is possible that a power tube shorted temporarily and blew the FUSE. If this is the case, it may work again nor120 V. 3 A. mally. To be extra safe you may want to replace all four power tubes in the shotgun 60 HZ. troubleshooting tradition and save the replaced set as spares. NOTE: Like tires on a car, spare tubes are always a measure of good insurance. Your DC-10 was carefully constructed with reliability in mind! Given the proper care and maintenance, it will deliver years of trouble free service. However, any pro guitarist who is out there gigging will tell you; spare tubes are a must for the fabled cord bag and may someday be worth their weight in gold. Spare fuses are also a very easy way to insure an uninterrupted performance.

PAGE 8

REVERB FOOTSWITCH: This 1/4" jack allows you control of the REVERB remotely when the (optional) Mesa/Boogie Footswitch is connected. This footswitch can be ordered by calling us direct, or by contacting your nearest Mesa/Boogie Pro Center.
SILENT RECORDING: This rocker switch which is located down under the chassis and selects between the live SPEAKER ON setting and the silent SPEAKER MUTE setting. This is a perfect solution for all-nighters! This switch mutes all of the signal at the power section driver stage, removing the need for a speaker load IN THIS POSITION ONLY!
NOTE: When this switch is set to the ON position, a speaker load must be maintained by either a load resistor of some type or a speaker itself. Failure to comply with this instruction could result in major damage to the amplifier. To be safe Leave your speaker connected !
SLAVE: This 1/4" jack and control provide a signal derived from the speaker jack. This works great for using the DC-10 as a master send to a processor or when additional power amps are needed for additional power. Some players use this patch point to derive an FX Send Signal and go to other amps for their wet sound, leaving the DC-10 dry for definition.
NOTE: Once a signal is taken from the SLAVE it can not be inserted back into the FX LOOP RETURN jack or a feedback loop will occur. Much like holding a microphone into the PA systems cabinets.a loud high pitched squeal will result.
The DC-10 Combo contains two 90 watt custom designed Celestion speakers and these are wired in series, producing an impedance load of 16 ohms. Obviously the optimum speaker connection scheme for headroom and power would be the 16 ohm jack, but feel free to try connecting the speakers to any of the SPEAKERS speaker output jacks. Sometimes a mismatch will lend a sonic character that you may find interesting or even preferable. When using two speaker cabinets rated for 16 ohms, it will be necessary to use a Y cable to connect both of these loads to the 8 ohm jack in order to maintain a proper 4 OHM 8 OHM 8 OHM 4 OHM 16 OHM impedance match. NOTE: Always use a load on the DC-10 when playing, unless you are recording direct and have the silent recording switch set to the MUTE position.Even then it is advisable to leave the speaker connected to avoid possible damage to the amplifier. Now that weve reviewed all the controls and features of your new DC-10, its time to play. The following are some sample settings that should get you well on your way to exploring the possibilities of your new instrument. Thanks and Enjoy!

PAGE 15

BIAS ADJUSTMENT: (Part of a continuous series)
BEAMCONFINING ELECTRODE ( )
CATHODE ( ) GRID ( , ) SCREEN GRID ( )

PLATE ( , )

Heres a question we often hear: Why doesnt Mesa put bias adjustments in their amplifiers? Well, theres a short answer and a long answer to this question.
Structure of a 6L6 / 5881 Beam Power Pentode.
The short answer is that during my 12 years of repairing Fenders, one of the most frequent problems I saw was bias controls that were either set wrong or that had wandered out of adjustment due to vibration. As any honest tech will tell you, theres lots of easy money to be made by sprinkling holy water on amplifiers. uh, what I meant to say is Your amp needed biasing. See what I mean? What customer is going to argue with that? It only takes a moment and a volt meter: The Fender diagram shows how: Adjust this trim pot for - 52 volts. Thats it. Nothing more. Now dont be fooled into thinking that tubes draw more or less bias, they dont. The way a bias supply is connected to a tube is akin to a dead end road, it just trails off to nowhere without really completing a circuit. Its a static voltage and regardless of what tube is in the socket or even if the tubes arent plugged in at all, it doesnt change the bias voltage a bit. So the end of the short answer is this: Since a bias supply needs to put out the right voltage and never vary, I wanted to build amplifiers that were individually hard wired to the correct values and NEVER needed adjustment. And for 25 years, thats how Mesa/ Boogies have been built. Time to change tubes? Just plug our tubes into any one of our amps and youre DONE. No tech needed. NO bills and no BS about biasing. And most important: The bias is RIGHT because it cant change! Now, you want the long answer? Heres more information on how our hard-wired bias avoids trouble. Please read on. But first, lets make an important distinction. Our business is designing and building high performance amplifiers. And for this we need tubes whose variance is within a narrow range. Our warehouse is full of rejects.oh, they work they just dont perform within our tolerance range. We have a very sophisticated computer - based tube testing system (nicknamed Robotube) that matches and measures tubes over seven important parameters. It can even predict which tubes are likely to have a shortened lifetime even though they work perfectly during the test. Because our business is building quality amps, we can afford to reject a lot of wayward tubes. The guys you hear complaining because Boogies dont have bias adjusters are primarily in the business of selling tubes - not amps. They dont want to throw away 30 percent of their inventory, so they promote the idea that tubes outside our parameters can be used to customize amplifiers and they criticize us because our amps cant be adjusted to accommodate their out-of-Mesa tolerance tubes. Now you might be thinking, But I thought you just said that tubes dont draw bias, therefore they dont effect the bias supply and thus it doesnt need to be adjustable. When you set the bias (whether its by selecting the right resistors, as we do, or adjusting a trimmer which is quicker) what you are doing is establishing the correct amount of idle CURRENT that flows through the power tubes. But you cant adjust the current directly, you can only change it by adjusting the amount of bias VOLTAGE that goes onto the tubes control grids.

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Voltage and current are NOT the same. Current is the AMOUNT of electricity, the quantity and is measured in amperes. Voltage is the degree of electric charge like the pressure to use the old water analogy. Let me illustrate how different voltage and current are: When you scrape your feet across a carpetted floor in dry, wintery conditions, your body can become charged with 50,000 to 100,000 volts of static electricity. And when you reach for the door knob, a spark jumps and you feel it! The voltage is super high but the current (measured in micro-amps) is tiny - otherwise you would die from electrocution. Contrast this with your car battery, which puts out a mere 12 volts. You can lay your hands right across the terminals and not feel a thing. Yet the amount of current available can run to several hundred amperes. enough to turn over a cold engine and get it started. So current and voltage are two totally separate electrical parameters though when you multiply them together, you get POWER, which is measured in watts. When you set the bias of an amplifier, you are adjusting the static VOLTAGE at the control grid of the tube in order to produce a desired amount of idle CURRENT flowing to the tubes plate. A small change in grid voltage, produces a large change in the amount of current flowing and thats basically how a tube works. Say that again because its super important: A small change in voltage at the grid causes a large change in current flowing to the plate. See, thats the essence of amplification: A small change causing a large change. And here its a small voltage change causing a large current change. The bias conditions are what determines how much current flows through the big power tubes when youre not playing. And what drives your speakers is flucuations in that current flow when are ARE playing. If the amount of current increases and decreases 440 times per second, then youll hear an A note. If the fluctions in current flow are large and still at 440 per second, youll hear an A that is LOUD! But for purposes of biasing, its the amount of plate current flowing with no signal applied thats important. Unfortunately current is hard to measure because the circuit must be interuppted as in cut the wire and the meter spliced in series with the broken circuit. But measuring VOLTAGE is easy. It is not necessary to interrupt the circuit because a voltage reading can be taken in PARALLEL with the circuit intact. Thus, as a matter of convenience, most bias settings are given in volts at the grid. even though current through the plate is the important factor. In fact plate current is so inconvenient (and dangerous) to measure that Fender doesnt even state what the correct value should be. They only give the grid voltage that will produce that current. (Thats the minus 52.) But that only happens if the tubes being used are in spec. As long as the tubes ARE in spec, the right bias voltage will always give the correct plate CURRENT but then theres no need for the bias voltage to be adjustable! If the tubes are NOT in spec, then the only proper way to re-set the bias is to cut the circuit and measure the current while adjusting the bias. but no manufacturer I know even STATES the desired current value! Be that as it may, when the original bias voltage is altered far enough, it will compensate for the tubes abnormal performance and the correct amount of idle current flow may then be restored. Clearly this is something most repair techs should not attempt. Some newer amps have LED indicators connected to the circuit which will turn on when the right threshold of current flow has been reached. This is an improvement, and almost worthy if youre willing to except resistors and lights added into your amplifiers audio path which we arent. The other advantage of this system is that it allows some amp manufacturers to avoid matching their power tubes. The thinking is that adjusting the bias to each tube separately eradicates the inherent differences between the tubes by insuring that the same current flows through each one. Again, this has some merit. but its still not as good as using tubes that are matched in the first place because compensating for the mis-match causes the push-pull circuit itself to become unbalanced. Two wrongs dont really make a right.

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Some of the other recommended biasing, methods such as -. tubes running red hot, increase the bias. sounds harsh and runs too cool, turn it down. are guesswork at best. Luckily, one of the great things about tube amps is that they can usually stand some abuse without causing any real harm. at least not immediately. But dont these alterations imply that you are second-guessing the amp designer and that theres a better set of operating conditions that the designer missed but the tube sellers have discovered? Now some players may like the sound of their amp altered by tubes with extreme characteristics and with the bias set to help compensate. But often it is the mere novelty of change that theyre really responding to and when the amp goes back to the proper original way, weve seen them be far happier still! Because every part in every one of our designs has been meticulously evaluated, compared and stressed over no matter how seemingly insignificant it might be. And with every design we look for a sweet spot where all the parameters including the bias come together to give the best sonic performance, consistently and reliably. Every part and voltage is important yet no one complains that these other parameters arent available for tinkering. Consider our patented Simul-Class circuitry where there are two different bias voltages used for separate pairs of power tubes. and changing one voltage also changes the other. Great care goes into getting this just right and we think wed be asking for trouble to have it adjustable for the world to play with. unless you like paying to have your amp messed up. Sorry, I meant to say, Uh,. your amp needed biasing. If that doesnt appeal to you, then merely plug a matched set of Mesa tubes into one of our amps and youre ready for tone. Guaranteed. Youd be amazed at the number of service calls we field every day that lead to a diagnosis of out-of-tolerance, non-spec tube problems. To think these would be prevented by including a bias adjustment is something of an insult to you and us. If you put the wrong size tires on your car, do you think changing the pressure will make them right? Please, dont think this is a blanket indictment of the other guys selling tubes it isnt. And their tubes arent all bad either. It just doesnt make sense to pay more of your hard earned cash for tubes that were probably made in the same Russian or Chinese factory and which have the possibility of being outside the performance window we select for your amp. And it pains us to hear the hype and mystique built up around biasing when twenty-five years of evidence affirms our decision to make bias circuits that never need adjustment. How much money and trouble that has saved Mesa/Boogie players you couldnt estimate. Our rigorously tested and hand selected tubes are available at your nearest Mesa/Boogie Pro Center or from us directly. Nobody offers better price, quality or warranty than we do. so why swerve? Next time well talk about our part in developing the great Sylvania STR 415 type and how were on the verge of seeing something fairly close reappear on the market. Remember, we still have some of these super rugged mondo-bottles available for older amps Boogies only please! Until then, Relax, Breathe and Nourish your soul! Cheers! Mesa/Boogie Ltd.

Randall Smith Designer & President

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PARTS SHEET: DC-10 Front Panel
JACK pt# 610120 KNOB pt# 409108 SLIDER BUTTON pt# 408535

( BOTH ROWS OF KNOBS )

POT pt# POT pt# POT pt# POT pt# POT pt# POT pt# POT pt#

SWITCH pt# 605373

SWITCHES ( all 3 ) pt# 601073

591842

POT pt#

591047

PILOT LIGHT BULB pt# 703047 PILOT LIGHT HOLDER pt# 703900 PILOT LIGHT LENS pt# 703784
JACK pt# 610123 GRAPHIC EQ pt# 588535

KNOB pt# 409115

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PARTS SHEET: DC-10 Rear Panel
FUSE HOLDER pt# 790342 FUSE pt# 2A MINI-TOGGLE SWITCH JACK pt# pt# KNOB pt# 408004 POT pt# 2737 KNOB pt# JACK pt#

408004

POT pt# 2737

618100

FUSE AC POWER

JACK pt # 612391

JACK pt#

618112

SWITCH pt# 600115 SPEAKER JACKS (all 5) pt# 618112

Thank you

for trusting MESA/Boogie to be your amplifier company. We wish you many years of toneful enjoyment from this handbuilt all tube instrument.
1317 Ross Street Petaluma, CA 94954 USA