Phase Linear Model 1000 Autocorrelator Noise Reduction System
You have just purchased the most advanced and most versatile noise reduction and dynamic range recovery system available. Proper use of your Phase Linear 1000 will allow you to reproduce music with less noise and greater dynamic range than previously thought possible. We hope you will read this manual thoroughly in order to appreciate all the benefits of the 1000. Recording studios and record processing companies employ a number of "necessarily evil techniques brought about by the state of the recording art. Taken together, these techniques may be described as processes which serve to limit and restrict the dynamic range of recorded material. Unfortunately, their use is necessary in order to put the tremendous dynamic range of live music onto the surface of modern phonograph discs and tapes. When used properly, the Phase Linear 1000 will significantly correct these shortcomings inherent in the recording process. Before leaving our factory your Phase Linear 1000 was tested and certified to be in perfect operating condition. This manual has been prepared to help you operate your Phase Linear as well as keep it in perfect condition. Your Phase Linear when used with care befitting all fine instruments, is capable of truly providing a lifetime of musical fulfillment.

CONNECTIONS

1. Check front panel to insure: a. The power switch is in the off position. b. The 1000s tape switch is in the source position (out). 2. Connect tape output on your receiver (preamp) to the input on the 1000 and connect the 1000s outputs to your receivers (preamp) tape input jacks. 3. Plug in the 1000s AC cord while leaving the unit turned off. 4. Turn on your receiver (preamp), and then turn on the 1000. 5. The tape monitor on your receiver or preamp should be in the monitor position. 6. Refer to the Operating Instructions for correct operation and adjustment of the Correlator and Peak Unlimiter circuits.
AUXILIARY EQUIPMENT Outboard units such as Dolby or DBX may be used with your 1000 but the 1000 must be placed after the units in the signal path and before any equalizer in signal path, or as shown.
Any source played through the 1000 will be processed. It is not necessary, therefore, to process a signal prior to recording since it will be processed on playback. However, if you wish to make a tape to be played back on another system, simply install the 1000 between source and the tape recorder. Note: It is not advisable to use the Expander during recording since it will stress the recorders dynamic range capability.

FRONT PANEL CONTROLS

Unlimit Threshold Lamp: Provides visual indication of peak unlimit operation. This lamp should come on during the peaks in the program material but should not stay on all the time. Unlimit Threshold: Rotate clockwise to increase dynamic range of program material. Adjust so that unlimit indicator lamp illuminates on peaks and extinguishes between musical peaks. This knob adjusts both the peak unlimiter and the downward expander. Low Frequency Calibration: Adjusts low frequency noise reduction. Once this is adjusted properly it should not be changed unless your cartridge or turntable is changed. An incorrect setting of this control will cause a loss of bass response. (See Operating Instructions) Correlation Threshold: Rotate counterclockwise to remove noise from program material. Correct adjustment is indicated by absence of random hiss and presence of all high frequencies associated with the musical program. Incorrect adjustment is indicated by complete loss of high frequencies or by presence of noise in the program. Typically, proper settings are found in the eleven to three oclock positions though this setting will vary with the source material. Power Indicator: Illuminates when unit is on. Power: Press in to turn unit on.
Autocorrelator: Press in to activate correlator. Peak Unlimiter: Push in to activate Peak Unlimiter/Downward Expander. Tape Source: Press in to use tape path on Model 1000.

OPERATING INSTRUCTIONS

AUTOCORRELATOR The AUTOCORRELATOR is a noise reduction system designed to remove noise from any signal source. The following steps should be used to adjust the AUTOCORRELATOR: Step 1: Step 2: Rotate the CORRELATION THRESHOLD control fully clockwise. Check to insure that the Correlator is turned on.
Step 3: Put on a good quality record, advance the treble controls to full maximum on your preamplifier or receiver. Select a portion of the record in which hiss may readily be heard against the musical program. Slowly rotate the Correlation Threshold counterclockwise. As the control is progressively rotated counterclockwise, a point will be reached at which the record hiss drops to a very reduced level while the high frequencies of the musical program remain unaffected. Further counterclockwise rotation will have no effect on the program until a rather extreme counterclockwise rotation results in an abrupt and complete loss of high frequencies associated with the music. The Correlator is said to be "in lock when the threshold control is set anywhere within the two limits outlined above. The correct setting is midway between these

two limits. This setting is rather broad and not at all critical. The action is very similar to the familiar "vertical-hold control on your television set. To far in one direction will cause the picture to "roll down. As with the vertical hold control on your television set, a CORRELATOR THRESHOLD setting too close to either extreme may cause the Correlator lock-in ability to become impaired and it may occasionally and briefly fall out of lock. This is caused by random disturbances on the record surface. The symptoms of this condition are: 1. If the control is set too close to the clockwise limit, the Correlator may momentarily fall out of lock and a brief noise pulse or burst will be heard against the music. 2. If it is set too close to the counterclockwise limit, a momentary loss of highs will occur. In general, a split second loss of highs is never noticeable, but even the briefest noise pulse is highly audible and extremely objectionable. This fact suggests that if you should have a record that seems to cause the Correlator to occasionally fall out of lock, the CORRELATION THRESHOLD should be set somewhat to the left (counterclockwise) of the theoretically optimum position. This will absolutely insure that an objectionable noise burst never occurs. After some experience has been gained in use of the noise reduction system you will find that the threshold adjustment may be made easily and quickly by ear without boosting treble. LOW FREQUENCY CALIBRATION ADJUSTMENT (L F Cal) L F Cal adjustment is an adjustment that is performed upon initial installation. Adjustment procedure is as follows: 1. 2. 3. 4. 5. With Correlation circuit engaged, apply as much bass boost with your preamp or receiver as possible. Rotate the L F Cal adjustment control fully clockwise. Turn down the main volume control. Put the phono stylus pickup on the blank portion of a lead groove on a good quality record. Advance the volume control until rumble and/or hum is heard in the speakers. Carefully rotate the L F Cal control counterclockwise until an abrupt drop in rumble and/or hum occurs. Rotate the L F Cal control slightly further counterclockwise past the drop-out point. You may verify correct operation of the Dynamic Low Filter by switching the correlator switch in and out. There should be no loss of bass material-only the disappearance of rumble and hum. This completes L F Cal adjustment and will require readjustment o nly it the pickup cartridge is replaced with a unit whose sensitivity varies significantly from the first. 6. You should make a mental note of the final setting of this adjustment in the event that it is inadvertently moved

THE DOLBY NOISE REDUCTION SYSTEM AND THE AUTOCORRELATOR The Autocorrelator differs from the Dolby system in that it is a single pass or open ended system which removes noise from the source without the necessity of the source material undergoing special encoding. The Dolby system is a noise preventing system designed to prevent additional noise from adding to the signal during tape recording. The Dolby system is a two pass or closed system which cannot remove noise once it has contaminated the signal, but prevents it from
increasing during the tape recording process Both systems provide approximately 10dB of signal to noise improvement. It is possible to obtain a full 20dB increase in signal to noise by operating the Dolby system in tandem with the AUTOCORRELATOR. A tape recording that has been "Dolbyized" during recording may be "de-Dolbyized" by a Dolby decoder, then processed through the 1000. An interesting psychological phenomenon occurs when high frequency hiss is removed from the program source. It often seems that the absence of hiss is accompanied by a loss of high frequency program material, when in fact, no loss has occurred. At first, with certain kinds of music, the psychological suggestion that high frequency material has been removed along with the hiss is very difficult to overcome. With other kinds of music, it is very obvious that only hiss has been removed. However, after a brief exposure to noise-tree music, this psychological phenomenon seems to vanish as one becomes accustomed to a noise free background. Once acclimated to a noise free background, it becomes rather unbearable to listen to hisscontaminated music. Historically, it took several years before Ray Dolby was able to convince the world his system was able to reduce noise without affecting the high frequencies. This situation was caused by the aforementioned psychological effects. PEAK UNLIMITER/DOWNWARD EXPANDER Actual operation of the Peak Unlimiter circuit is relatively simple. Initially, set threshold control to the full counterclockwise position with the circuit engaged and source turned on. Gradually rotate the threshold control knob clockwise until the peak indicator lamp flashes on the peaks of the program material. The indicator lamp should NOT stay on all the time. No setting is necessary for the downward expand circuit since it is automatic
CHARACTERISTICS OF THE EXPAND CIRCUIT The threshold adjustments will vary with the type of program material being played due to the different degrees of compression and gain riding used at the studio. You will find that the threshold setting for phono is different from either FM or tape sources. Generally the more compression used in recording and broadcasting, the more difficult it will be to make the indicator lamp flash on the peaks. It will want to conti nuously stay either on or off, which is not an optimum setting. This is because there are few if any peaks to expand due to excessive compression. MAINTENANCE & SERVICING CLEANING To keep your 1000 clean and looking like new, occasionally clean the front panel with a soft paper towel and full strength ammonia This will remove dulling films which have a tendency to build up on the brushed finish. REPAIR FACILITIES Only qualified technicians should be allowed to repair your Phase L near 1000. The Phase Linear Corporation and its authorized warranty stations have the trained personnel and special equipment required to repair your unit. Should you have any trouble with your unit write to the

factory for the address of the nearest repair facility Please include the model and serial number of the unit together with a description of the problem. RETURN AUTHORIZATION No preamplifier should be returned to the factory without an Authorized Return card which will be supplied by Phase Linear. Write to the factory in care of the Service Department for the authorization. Packages returned without an authorization card will not be accepted. SHIPPING Never ship your Phase Linear in any shipping carton other than the original or a replacement supplied by Phase Linear. For a replacement write to the factory or see your local dealer. If the preamplifier is shipped in other than a Phase Linear cart on which is properly packed, all damages must be paid for by the store or person shipping the unit. Ship only via a reputable carrier. DO NOT USE PARCEL POST! Insure the unit for the full value and double check to ensure the unit is properly packed. DESCRIPTION OF CIRCUITS PEAK UNLIMITER AND DOWNWARD EXPANDER The Dynamic Range Recovery System The peak unlimiter, together with the downward expander, combine to greatly increase the available dynamic range. Before discussing the system several words should be defined. Compression is the function of intentionally altering the musical signal level in such a manner that loud musical passages are recorded more softly, and soft material passages are recorded more loudly than the live counterpart. Peak compression refers to the compression operation being performed exclusively on brief musical peaks and is generally referred to as peak limiting. Low level compression refers to the compression operation performed on very low level signals and normally compresses the average signal level. This operation is generally referred to as low level gain riding or upward compression When a phonograph record is made, compression is performed by the combination of an electronic compressor together with the skillful application of manual level changes by the recording engineer (gain riding). During high level musical transients, a device called a compression-limiter or peak limiter is employed at the recording studio to compress and limit the level of musical peaks. This is necessary to prevent a system overload associated with the mastering of the phonograph record. During quiet, low level passages, the recording engineer manually raises the overall recording gain in order to produce a recording that will be loud enough to cause the background noise level to be acceptable The peak-unlimiter is designed to restore to a significant extent the musical peaks that are removed by the peak-limiter during recording. The amount of peak-unlimiter operation is a function of the time rate of change, the duration, and the instantaneous level of the input signal (the recording). Tracking is designed to closely compliment the dynamics of recording studio peaklimiter. The maximum amount of unlimit action is + 1.5dB and the maximum attack rate is.5dB/micro second The goal of this system is to expand the dynamic range of standard (uncoded) musical material such that the loudest passages wilt produce levels of 105dB and yet during quiet passages noise or hiss will not be heard. In addition, the dynamic range expansion system must not cause any detectible sonic anomalies such as breathing, swishing or any obvious volume manipulation. Basically, dynamic range expansion entails making the loud parts louder and the soft parts softer in a way which significantly improves the dynamic range of music in a manner which does not make it sound as if the volume has been changed. It is possible to make small

changes in volume that go undetected. It turns out that at high levels (above 90dB) a volume increase or decrease of 1.5dB is the maximum tolerable before change is perceptible. At very low levels, a change of 3.0dB is possible without detection Since it is desirable not to hear the system operate, the maximum possible expansion would be only 1.5dB. And the question arises. why bother? The Peak UnlimiterHow It works: At very high levels, the gain of the system is increased by 1.5dB, while at levels just below this the system gain does not change at all. During moderately soft passages the system gain is changed with variations in program level by an amount of 1dB in every 10dB (i.e., if the input level changes 10dB the output will change 11dB) with an allowed cumulative maximum of 3.0dB. -that is the linear expander. During very soft passages the gain is changed by 3.0dB. -that is the downward expander. Conceptually, the scheme has been to limit any individual expansion operation to an amount small enough to be undetectable and only to operate on the extremes of the loudness spectrum. Summary: The Phase Linear Dynamic Range Recovery System selectively expands (peak unlimit 1.5dB, linear expand 3 0dB and downward expand 3.0dB) in a way that produces no audible side effects and yet yields a significant total increase in dynamic range of approximately 7.5dB. That is a dynamic range increase of over tour times in terms of radiated power. This, when combined with the autocorretator, yields a 17.5dB increase in effective signal to noise ratio and dynamic range.
THE AUTOCORRELATOR The following description of the Autocorretator was related to Bert Whyte by Bob Carver, President of Phase Linear, in the April, 1975 issue of A udio Magazine. The article was written by Bert Whyte: Music energy appears in discrete energy bundles throughout the audio band and is therefore not continuous. In addition, if some musical energy appears, for example, at a particular frequency, we know for certain that even and odd harmonics will exist simultaneously throughout the passband, and that energy will not exist between these harmonics. In other words, with music we are able to predict where energy is likely to occur, if we know where the fundamental is, or even if we know where on/y one of the harmonics is. Also, and importantly, we know where the energy will not appear. In other words, music is coherent or correlated. Since pure hiss is totally uncorrelated, it is assigned a correlation co-efficient, which is zero. Highly correlated signals, such as sine wave or a linear sum of sine waves, have a correlation co-efficient of one. As noted, music is a correlated signal, but the correlation value of music varies continuously from moment to moment. The Autocorrelator may be considered a real-time Fourier analyzer with correlation co-efficient estimator. It's a very complex circuit, and the following is a simplified explanation of how/f works: A series of electronic gates or windows, each window controlling a certain frequency range and lust overlapping its neighbor, is p/aced in the audio passband. These windows can be either closed or open. If it is closed, energy, be it correlated (music) or uncorrelated (noise), cannot be transmitted at that point in the frequency spectrum assigned to the particular window. If the window is open, energy may be transmitted at that frequency. An operational description from Phase Linear says that each window is controlled by two sets of control circuits coupled together by diode logic OR gates. The primary circuit is located in the control band, between 200Hz and 2kHz. The secondary circuits are located throughout the harmonic band, if above a level of -65dB, will cause each window associated with the appropriate harmonic to open. If energy appears in the harmonic band at a particular frequency, each window associated with each upper harmonic

of that frequency will be opened. All lower windows will remain closed. Notice that as the frequency increases, fewer and fewer windows are required to be opened. Notice also that for the autocorrelator to recover a harmonic buried beneath the noise, it's necessary that the harmonic have associated with it a lower frequency fundamental whose energy level is above the noise. Fortunately, this condition is common in musical energy. In similar fashion to most noise reduction systems, the autocorrelator commences with a reduction of 3dB at 2kHz, and reaches 10 to 12dB from 4kHz to 20kHz. As noted, the device has a circuit which estimates the degree of correlation of incoming signals and generates a control signal. This correlation function signal is combined with another signal which indicates the harmonic content of any incoming music energy. This controls a threshold le vel designed to detect musical information within each of the bandpass frequencies. It must be appreciated that in the music output of phono disc or tape, the noise (hiss or uncorreIated sound) is always present outside the gates, and is always ready to rush in along with the music when a gate is opened. By automatic adjustment of the various threshold levels at which the bandpass gates are opened, the incoming signal passed through the gates is almost always of such amplitude, frequency, and correlation that the wellknown masking phenomenon occurs, and the noise is subjectively covered. SPECIFICATIONS TOTAL DISTORTION: Less than.250%. INPUT IMPEDANCE: 70k ohm INPUT LEVEL: 3 volts R.M.S. maximum OUTPUT VOLTAGE: Full output 8 volts R.M.S. Better than 3 volts R.M.S. into 2000 ohms. FREQUENCY RESPONSE: Within 1dB from 20Hz to 20k Hz. PEAK UNLIMITER: (Nominal peak unlimit rate attack threshold, front panel variable).5 dB/micro second for +6 dB peak unlimit operation. NOMINAL AMPLITUDE ATTACK THRESHOLD: 2 volts peak at input to peak unlimiter. SEMICONDUCTOR COMPLEMENT: 28 transistors, 8 integrated circuits, 91 diodes DOWNWARD EXPANDER: Downward expansion commences at -35dB Ultimate limit is -41dB. Unlimiter window is 35dB wide, upper and lower thresholds are simultaneously variable by front panel unlimit threshold control. AUTOCORRELATOR (NOISE REDUCTION SYSTEMS): High frequency noise reduction commences at 2kHz and is 3dB, reaching 10dB from 4kHz to 20kHz. Low frequency noise reduction begins at 200Hz, ultimately reaching 20dB @ 20Hz. Passive subsonic filter rejection of -35dB @ 5Hz. Weighted overall noise reduction is -10dB from 20Hz to 20kHz TAPE MONITOR: The Model 1000 provides a tape monitor circuit to replace the one it utilized. POWER CONSUMPTION: 35 watts. SIZE: 9 1/2" wide x 5 high 11-4/5 deep. WEIGHT: 6 pounds, Warranty: Three years, parts and labor.

THE B.A.S. SPEAKER

Coordinating Editor: Michael Riggs Production Manager: Robert Borden Copy Editor: Joyce Brinton Staff: Richard Akell, Stuart Isveck, Lawrence Kaufman, John Schlafer, James Topali, Peter Watters, Harry Zwicker THE BOSTON AUDIO SOCIETY P.O. BOX 7 BOSTON, MASSACHUSETTS 02215
VOLUME 4, NUMBER 8 MAY 1976
THE BOSTON AUDIO SOCIETY DOES NOT ENDORSE OR CRITICIZE PRODUCTS, DEALERS, OR SERVICES. OPINIONS EXPRESSED HEREIN REFLECT THE VIEWS OF THEIR AUTHORS AND ARE FOR THE INFORMATION OF THE MEMBERS.

In This Issue

In his first article ( BAS Speaker , March 1976), John Gombos described a filing system that he has used for eleven years. Gombos follows up that piece in this issue with one that should be of particular use to the Society's members: a subject guide to the Speaker from Volume 1, Number 1, through Volume 4, Number 5 (Oct. 1972 through Feb. 1976). We return this month to the subject of tonearms. Mike Riggs discusses the oft mentioned but seldom explained specification "effective mass" and casts a critical eye on the significance of "seesaw frequency," as championed by David Gammon of Transcriptors. It is therefore especially appropriate that this issue includes reports from two members on their experiences with the Transcriptors Vestigal arm. Mark Dimirsky, from Manitoba, solved the Vestigal's problems by replacing it with a SME, while Rhode Island member Jeffrey Nelson discovered the Formula 4. Nelson and California member Dow Williams present in this issue the firstto our knowledgereviews of the Formula 4. To round out this month's series of users' reports, California members Steve Seto and Nate Garfinkle review the Phase Linear 1000 and the Quad 405 current dumping amplifier, respectively. Application Forms You may have noticed that the past two issues of The Speaker included an application form. We hope that you will pass the form along to a friend who might be interested in joining the BAS. We will be sending you renewal forms for 1976-1977 sometime in the late summer.
Membership dues are $12 per year (October 1 to September 30) or portion thereof. Dues include a one-year subscription to the BAS Speaker. ( Note that almost the full amount of dues is allocated to production of the Speaker. The local activities of the BAS are strictly self-supporting.) For further information and application form, write to: The Boston Audio Society, P.O. Box 7, Kenmore Square Station, Boston, Mass. 02215.
Copyright 1976 The Boston Audio Society
Vol. 4, Num. 8 May, 1976 OCRed from printed copy - errors possible.

The BAS Speaker

BAS Speaker Mailing The BAS Speaker is now mailed to more than 600 people, and this is causing us some difficulties. With that many copies to be addressed and put into envelopes, it is no longer possible to do the job at the monthly BAS meeting. As a result, we are trying to gather a group of volunteers to take care of the mailing during the week following the meeting, and this means that copies are often not mailed until the end of the month. So, be patientyour issue will arrive, but later than it used to. Any Boston-area member who can help with the mailing project should contact Joyce Brinton or Al Foster at meetings or via P.O. Box 7. Volunteers are desperately needed, particularly if we are to avoid having one group do the work every month. In fact, if someone would be interested in taking responsibility for organizing the mailing, that would also be appreciated. For Sale Sony TTS-3000A with SME 3009. Joseph Gemmato, (617) 254-7796.
An Interesting New Amplifier
David Berning, a founder of The David Berning Company (11007 Candlelight Lane, Potomac, Maryland 20854) and designer of the Berning EA2-150 power amplifier, is a physicist at the National Bureau of Standards. His amplifier is a hybrid design, i.e., it uses both tubes and transistors. It has very little negative feedback (what's there can be cut out entirely with a switch on the front panel) and uses TV horizontal output tubes rather than conventional audio tubes. Berning has designed the amplifier to be unusually efficient, so as to make it run cooler and more reliably than other tube designs. Power output is 150 watts per channel. This would seem to be the per-. feet amp for individuals with large rooms, inefficient speakers, a disdain for "transistor sound," and $850 looking for something to buy. Berning also makes a hybrid preamp, which he tells me passes the Holman square-wave test with high marks. This goes for a mere $ 275. I have heard the Berning amp-preamp combination driving Magneplanar T-III's. The sound was very impressive indeed. Bill Bell (Washington, D.C.)
A Preamp-Cartridge Switchbox
Abbott Lahti (Power Systems, Inc., 56 Bellis Circle, Cambridge, Mass. 02140) has designed an excellent preamp-cartridge switchbox. The switchbox can be used to do A-B comparisons of preamplifiers without adversely loading them or affecting their performance, and it is completely passive. In addition, there are no pops or clicks when the cartridge and the preamp inputs and outputs are switched. Some points to remember when assembling your switchbox are: 1. The 4-pole, 2-position switch must be a "make-before-break" (shorting) type. 2. It is not necessary to use shielded cable inside the switchbox, but a metal housing is a necessity. 3. Low-capacitance cables must be used from the cartridge to the switchbox. The cables to the preamps' phono inputs also should be low capacitance, and identical to both preamps, to ensure equivalent capacitance. Most switches add about 20 to 30 pF, which is equivalent to about 1 foot of a good cable. 4. All the grounds on the low-level side of the box are tied together and floating. 5. The high-level grounds are connected to the metal case.

Penguin Stereo GuidePart II
This is a continuation of the list of outstanding records begun in last month ' s Speaker. Brian Leeming has culled these discs from The Penguin Stereo Record Guide , which has given them their highest rating. All are available from the BAS Record Importing Service.
Handel, Concerti Grossi, Op. 3, 1-6, Op. 6, 1-12, Marriner, ASMF, Decca SDDB 294-7. (Op. 6 is available in the U.S. as London 2309). Haydn, Symphonies (complete), Dorati, Philharmonia Hungarica, London STS 15310/15, 15257/62, 15249/54, 15127/30, 15131/4, 15135/8, 15182/5, 15229/34, 15319/24, 15316/7. Haydn, Piano Trios (entire series), Beaux Arts Trio, Philips 6500-521, 522, 401, 023, 400. Haydn, String Quartets 44 and 45 (Prussian), Tokyo Quartet, DGG 2530 440. Haydn, String Quartets 74 and 77, Berg Quartet, Telefunken 641 302. Honneger, Symphonies 2 and 3, Karajan, Berlin Philharmonic, DGG 2530 068. Lehar, The Merry Widow (complete), Matacic, Philharmonia Orchestra, HMV SLS 823 (2 discs). Liszt, Piano Concertos 1 and 2, Brendel (piano), Haitink, London Philharmonic, Philips 6500 374. Liszt, Piano Concertos 1 and 2, Richter (piano), Kondrashin, London Symphony, Philips 835474. Liszt, Piano Music (Sposalizio, II penseroso, etc.), Brendel, Philips 6500 420. Mahler, Fourth Symphony, Raskin (piano), Szell, Cleveland Symphony, Columbia MS 6833. Mahler, Fifth Symphony, Barbirolli, New Philharmonia Orchestra, HMV SLS 785 (2 discs). Mahler, Eighth Symphony (Symphony of 1000), Solti, Chicago Symphony, London 1295 (2 discs). Mahler, Ninth Symphony, Haitink, Concertgebouw Orchestra, Philips (2 discs). Mahler, Five Ruckert Lieder, Janet Baker (mezzo-soprano), Barbirolli, New Philharmonia Orchestra, HMV SLS 785 (2 discs). Mathias, Dance Overture 16 and Harp Concerto, Ellis, harp, Atherton, London Symphony, Welsh National Opera Choir, L'Oiseau Lyre S-346.

Ensayo on MHS

Below is a list of Ensayo recordings used on the AR demo disc that are available from The Musical Heritage Society. The sonic quality of the MHS pressings is up to that of the AR record, but (as Mike Riggs has pointed out) they are not as quietjust average. MHS AR Side 1 Bands 1 & 5: Igor Stravinsky, "L'Histoire du Soldat" Band 2: Pablo de Sarasate, "Nine Spanish Dances" AR Side 2 Band 4: "Music of the Late Middle Ages and Renaissance" 1141 Ensayo ENY-20 ENY-3 ENY-37
Another MHS disc worth considering is Maurice Ravel's "Trio for Piano, Violin, and Cello" and "Sonata for Violin and Piano" (MHS 1235). I have not heard the original of this Harmonia Mundi recording, but the MHS version is excellent. Christopher Gupta (Ontario)

In the Literature

[The current editor of this column will be retiring over the summer; interested replacements may apply at P.O. Box 7.] Audio, May 1976 Build a Binaural Mike Set: A simple project for the recordist; uses rather unsophisticated construction, but might be fun to try. (p. 34) Record Cleaners: A survey of the devices on the market. Meaningful comments are scarce. (p. 40) Equipment review of the Pioneer RG-1 Dynamic Processor; also short of data. (p. 62, 75).

Wireless World, March 1976 As TIM is to Audio , so phase effects in loudspeakers are to WW: Phase and Sound Quality (". no significance. in a mono channel [of a stereo system].") (p. 80); Audibility of Phase Distortion, Letter (p. 60). Detailed technical articles on the WW FM tuner and on FM waveforms. Wireless World, April 1976 More on phase effects in loudspeakers: Phase Shift in Loudspeakers, Causes And Measurements (p. 73); Phase Effects in Loudspeakers, Letter (p. 53). Current Dumping Audio Amplifier, Letter (p. 54) Transistor Driver for Valve [Tube] Amplifiers (p. 36) More on WW FM tuner and FM waveforms.

April BAS Meeting

Business Meeting
D. Craig, H. Zwicker, M. Riggs
The BAS is homeless again. We met this time in an auditorium on the MIT campus, and the first order of business was a call by Jim Brinton for people who might have access to suitable meeting sites. Al Foster will be bulk ordering Maxell UD-35 open reel tape. Prices are not yet set, but bargains are promised. Get in touch with Al. Also coming from Al Audio-Technica test records. More information shortly. Attend the meetings for further word. J. K. Pollard solicited interest in the Audio Amateur's latest modifications to Heathkit's popular IG-18 audio generator. The magazine will offer printed circuit boards if there's enough interest. Al Foster announced a Speaker mailing session and called for volunteers. [Total attendance was three, making it an all-night job. Volunteers are sorely needed to make this a more manageable chore. Here's a chance to contribute to the success of your organization, hear some good sounds, chat with people of like interests, and get to know one of your BAS officers as something more than a vendor of tape and record bargains. H.B.] This month's thieves' market featured Dr. Brian Leeming's overseas record service. Prices are lower than for the same records purchased statesidetake advantage. Jim Brinton delivered some Mark Davis preamps. Abbott Lahti had his phono preamps and phase-locked multiplex modification kits for sale. Ira Leonard had Insight Records' "Fidelity FirstAn Unrehearsed Experiment." The newer "Pig's Eye Jass" is on order. And Peter Mitchell had mike cable, the last BAS oscillator, and, for the right person, a single 814 mike capsule. Meeting Feature: Peter Pritchard Our guest speaker was Peter Pritchard, formerly the President of ADC, where he designed cartridges and the tonearm that bears his name. He now presides over Sonic Research, also a maker of state-of-the-art cartridges. On the face of it, Mr. Pritchard could not have presented a greater contrast to last month's lecturer on tonearm design, Jacob Rabinow. The glib Rabinow presented the image of the compulsive inventor pushing forward the innovations sometimes at the expense of unrefined details. Peter Pritchard spoke in carefully measured words and seemed a man bent on the development of designs based only on carefully measured parameters at every stage.

The other Sonus cartridge is the Silver Label, which comes with either the elliptical or the Pathimax stylus. This cartridge is a ruggedized version with somewhat lower compliance and a heavier suspension, making it usable in a wider range of arms. According to Pritchard, its laboratory measurements are equal to or even better than the Blue-Red-Green cartridge, but the sound is not as open or effortless. Prices in the Boston area run from about $40 (for the Silver E) to about $86 (for the Blue). There's also a Blue Calibrated, which is a selected Blue supplied with a frequency run. When its time to change styli, return it to Sonus and they will replace the stylus and supply a new response chart. According to Pritchard, the cartridge pickers at the factory pick the Blues with the best frequency runs to become Blue Calibrateds. Pritchard recommends the Blue as having a smoother frequency response. Because the Pathimax contacts a larger surface area on the groove walls, the groove gives less and the stylus traces better on heavily modulated inner grooves. It should give better record wear than the elliptical tip. Even using higher-than-usual tracking forces, Sonus has been able to play records one or two hundred times without discernible wear. The stylus was chosen to take advantage of its better shape and not for CD-4 (though they feel it's a good CD-4 cartridge). Careful alignment is necessary to realize its full potential, however. Pritchard recommends that after adjusting for minimum tracking error, one place a pocket mirror on the turntable and look at the tip from directly overhead to check for vertical alignment. Design Factors. So how does one design a good cartridge? What are the parameters? First, says Prtichard, the basic design principle is not critical to the final achievable result. One can use moving coil, moving armature, or something more exotic. The choice boils down to economic factors and to ease of design and manufacture. The more important problem, says Pritchard, is achieving accurate transmission of the motion of the tip to the generating element. It's particularly difficult to get all motion transferred. In this respect, the ideal would be a massless, infinitely rigid, cantilever-armature system. Because the ideal doesn't exist, cartridge makers have to deal with resonances. One way is to taper the cantilever. That suppresses fundamental beam resonances, but not higher order harmonics. Sonus chooses instead to make the cantilever as short and light as possible. This also helps reduce the total mass of the moving parts. Any mass becomes a storage point for resonances. When the stylus beam is long, nodes tend to build and the actual pivot point of cantilever-armature starts to wander, perhaps as much as 10 mils or so. By keeping the cantilever short, there's very little motion wasted in torsion. The mass of the armature is held down by using very thin, magnetically permeable material and by keeping it very short. The suspension system and the armature have square cross sections, to hold the pivot point firmly in place and suppress rotational motion. Sonus aimed for perfect symmetry of the moving parts. This contributes to good separation of transients and to steady-state separation that continues to the top of each cartridge's range. The production cartridges are not as good as the laboratory models in this respect, but the production models have to have enough stylus clearance to play ordinary records. A useful feature of the Sonus' electrical design is low impedance. Inductance is about 100 millihenries and resistance is 300 ohms. This makes it easy to match cartridge and preamp, and it helps also when the Sonus Blue Label is used for CD-4. Pritchard also explained that it's nearly impossible to lower mass by using a nude diamond. In such styli, the diamond is secured by having a very thin sliver of diamond extend through the cantilever shank, where it's secured with something like epoxy cement. If one doesn't use enough cement, the stylus wiggles in the shank, and if one does use enough, the mass advantage is lost. The Sonus approach is to bond the tip to a tiny bit of steel. The steel is readily enchored to the shank without significantly adding to mass.

Distortion. Pritchard feels one really can't be sure what kinds of distortion predominate in cartridges because it's difficult to say how good the test record is. A cleanly recorded midfrequency sine wave can be reproduced with 0.1% to 0.2% THD. What distortion exists results chiefly from geometry and is random in nature, so it doesn't show up as even-order harmonics. IM tests don't tell much either, because they look at sum and difference products. For that matter, visual spectrum analyzers don't tell that much because (again) the distortion is mostly transient in nature. The best bet for finding cartridge distortion, says Prtichard, is an oscilloscope and a trained eye. Some hysteresis distortion is inherent in moving armature designs, but it can be minimized. The moving armature is charged to the point of saturation. If it's a little less than saturated, flux density in the armature will change as it moves toward and away from the pole pieces and charging magnet, especially at high velocities. In the Sonus, the problem was met by using a very powerful charging magnet and a short armature, and by placing the magnet over the pivot point, so the armature is fully enveloped in the magnetic field and its position relative to the field is effectively unchanging. A side benefit is that the magnet doesn't mechanically bias the stylus. Do Stylus Suspensions Self-Destruct? Well, they're known to come apart, but so far as Pritchard can discover, stories about suspension materials deteriorating are untrue. When the suspension fails, it's most likely because something has come apart. Cantilevers, on the other hand, do deteriorate. They're usually made of very thin aluminum and are protected only by the aluminum oxide that forms on the outside. The shank is just thousandths of an inch thick, and it can go. ADC had stylus assemblies coming undone because the cantilever and armature were made of different metals, and there was an electrolytic reaction between them. Sonus puts a plastic barrier between cantilever and armature. A Sonus Arm? There's a Sonus arm on the back burner now. Pritchard would like to make it an integrated arm-cartridge that could be de-integrated by the user when he got the urge. But integrated designs have never been commercial successes. Dealers react negatively on the basis that the audiophile simply doesn't want to give up the privilege of interchanging cartridges of different manufacture. The Sonus arm would be a modernized Pritchard, making use of materials not available when the original arm was designed (as an answer to the SME, which was at that time too massive and undamped for the ADC-1). It would be as light as possible and its cross section would change along its length. These features would make it a low-mass, non-resonant device. It would have a simple, damped pivot, and its overhang would be less than that of many current designs. A large overhang reduces tracking 'error, but adds to skating force. He prefers to hedge the compromise in favor of lower skating force, because anti-skating devices put an unwanted load on the stylus suspension system. Not only must it provide uniform restoring force to the stylus to keep it on the record, but it must counter the anti-skating device's tendency to pull the stylus off center. Though Pritchard would choose to damp his arm, he agrees in principle with Rabinow to the extent that there are other ways of attacking the problem. Pritchard said that "if you can design everything else to its optimum, then you don't need damping." And yes, he and Rabinow are still talking. Sonus Speakers? Maybe. But don't hold your breath. The field is so fiercely competitive and all the commercial angles so well covered that Pritchard will enter only if he can make a material contribution to the technology.

Unfinished BusinessADC. The present ADC Super XLM Mark II is not Pritchard's design. After BSR bought out the company, they asked for a CD-4 version. Pritchard added a Shibata stylus to the XLM but wasn't happy with the result, so he shelved it to work out a new design. After he left, BSR dusted off the cartridge on the shelf, made it a little more rugged, and called it the Mark II. In theory, it should track inner grooves better, but he doesn't know what kinds of tradeoffs were made in the redesign. Peter Mitchell pointed out that print reviews generally have panned the cartridge for CD-4 use. Someone wanted to know why ADC cartridges were so compliant that an arm with negative mass was needed to achieve a fundamental resonance between 10 and 20 Hz. Pritchard challenged the assumptions. In the first place, the cartridge was designed for a combined resonance of about 6 Hz. And in the second, their experimentation showed a resonance of about 10 Hz in typical record changer arms. You pick your tradeoffs, said our guest. A lot of room resonances occur around 10 to 20 Hz, as does much of the feedback transmitted by resonating records, so ADC chose to put the basic resonance lower. True, record warps ought to show up occasionally in that area, but in practice they hardly ever do. Besides, if one keeps the Q of the resonance low enough, there won't be any real trouble. And finally, 6 Hz is a good match to many of the low-cut filters on preamps. Marketing Footnotes. Pritchard agrees that there's a lot of opportunism in cartridge pricing. This results from market competition and from the fact that much of the public needs a high price to convince it that the puny little cartridge is as important as the electronics or speakers. Moving coil designs have an advantage in this area, because they really are exceptionally expensive to make. Their prices are high even when discounted, and people assume they must be good because they are expensive. There was a time when moving coil designs enjoyed an advantage in having low-mass moving elements, but with modern materials, he feels this gap has been closed. A recent ad for Sonus cartridges recommends the different stylus configurations of the premium cartridge for different arms. That piece got out without Mr. Pritchard seeing it. As soon as he saw it, he ordered it withdrawn. Any of the cartridges can be used in a high-quality arm. There was a question about the GE cartridge. Pritchard had worked on that classic, and it came about as close as any design has to becoming a universal standard. What happened, and could it be duplicated? Yes, said Pritchard, the GE was a dream almost too good to be true. It was a sound, economical, reliable, rugged design optimized over a period of years. The highly competitive, cut-throat cartridge market hadn't yet developed, and GE was able to control its market through a system of franchised dealers. They had 75% of the cartridge market wrapped up in their corporate grasp, as only a giant corporation could. And they lost it all in six months, as only a corporate giant could. Up there in the clouds they got a little short-sighted. Stereo, they thought, was only a gimmick that would fade away. When it didn't, they did a patchwork job on the classic design, ruined it, and thereby hastened their decline. Such a utopia will never happen again, mused Pritchard. And yet, for all we know, they could sweep the technology out from under us, Tomorrow, we could be playing records with laser beams. Get out the stardust and start sprinkling. Henry G. Belot

Dymek DA-3 AM Antenna... Feb. 76 CASSETTES
Chrome Cassette TapeAre They the Same?... Jan. 76 Capitol Music Tape C-90 Cassettes.. Feb. 76 CASSETTE PLAYERS

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Advent 201... May 74 June 74 Aug. 74 Feb. 76 Lafayette RKD-50... Aug. 74 Nakamichi 1000...July 73 Sony TC-152SD... July 74 Aug. Cassette Decks vs. Revox A-77...Aug. 74 Cassette DecksDanger to Heads... Oct. 74 GRAPHIC EQUALIZERS
Norman Lab No. 5 Acoustic Equalizer... June 74 SWTP Octave Equalizer... Feb. 76 HI-FI GENERAL

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A Cheap, Simple, Good Audio Oscillator.. July 74 The BAS Oscillator... Aug. 75 Sept. 75 Oct. 75 Nov. 75 Dec. 75 Feb. 76 Radio Shack SPL Meter....May 75 Building a Sound Level Meter..Sept. 75 How To Build a Pink Noise Generator... Jan. 75 Feb. 75 Apr. 75 Acoustech Product Improvements.. Feb. 76 Advent Business Problems... Nov. 75 Advent/Wollensak Electronics...Feb. 76 Audio Dealer/Customer Interface.. Dec. 74 E.P.I. Products... Sept. 74 IC Construction Hints... Sept. 74 Choosing Resistors for Audio Circuits.. Sept. 74 Choosing Op Amps for Audio Circuits... Sept. 74 Designing Simple Audio Circuits.. Sept. 74 How To Design With Op Amps... Sept. 74 Designing Audio Filters... Sept. 74 Active Filter Design....Sept. 74

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Component Compatibility...May 74 Clean Plugs for Better Response...Feb. 76 Weak Links in a System & How To Fix Them..June 75 Hum in Audio Equipment... Feb. 74 FCC Rule on RFI in Audio Equipment... July 75 Meaning of Specs & Related Sound...Feb. 74 Transient Response....Feb. 74 Phase Distortion & Transient Response..June 75 Radio Electronics Hi-Fi Test Reports..June 75 Notes on Product Testing...Oct. 73 HEADPHONES

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Making a Compact Headphone Amplifier..June 75 Aug.75 Jan. 76 Heil Full-Range Stereophones...Feb. 76 Koss Headphones....Mar. 75 Lafayette Earphone No. 40F78010...Sept. 75 Stax SRX3/SRD7 Headphones...Feb. 76 How Headphones Are Designed & Made...Mar. 75 LOUDSPEAKERS
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Advent 2....Oct. 73 Allison One.... Nov. 74 July 75 Aug. 75 Sept. 75 Oct. 75 Avid Model 103... July 74 Dahlquist Speaker Evaluation....June 74 Dahlquist DQ-10....Jan. 75 Dayton-Wright XG-8 Electrostatics... Feb. 76 Electro-Voice Super Woofer... Dec. 75 ESS/Heil Speaker.... June 73 Fulton J-Modular....Dec. 75 Heil Air-Motion Transformer...Feb. 76 Heil Woofer.... Feb. 76 Ionovac Tweeter.... Jan. 76 Janszen 130 Electrostatic Midrange/Tweeter..Jan. 76 Koss Electrostatic Speaker...Mar. 75 Sept. 75 Quad ESL....Feb. 76 Rectilinear 3 New Midrange Speaker...Jan. 76 Restoring Rolled Off Bass...Mar. 74 Checking & Compensating Bass Response..Aug. 75 Electronic Crossover Design....Sept. 74 Room Placement of Folded Horns...Dec. 75 Speaker Placement...Dec. 75 Myth: Corner Placement = Better Bass..June 75 Pairing Loudspeakers...Mar. 75 Loudspeaker Performance Limits...Apr. 75 Improving the High End of Your Speakers..Jan. 76 Speaker Efficiency: An Initial Review..Aug. 73 Speaker Impedance Measurements.. June 75 Aug. 75 Speaker Impedance vs. Power Amp Requirements.. June 75 Speaker Measurements... July 75 Oct. 75 Checking for Sloppy Speaker QC..Sept. 75 Dec. 75

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Insight Records...Dec. 75 Musical Heritage Society Records... Dec. 75 Pulse Code Modulation Records... Dec. 75 Sheffield Labs II... Nov. 75 Sheffield Labs III.... Oct. 74 Pixall Record Cleaner... Nov. 75 Cleaning Records With Vinegar...Sept. 75 Discwasher Record Cleaner... July 75 Clean Records for Cleaner Sound...May 73 Freon 11 as a Record Cleaner... Feb. 74 Vacuum System for Cleaning Records... Oct. 74 Nov. 74 Comments on Records & Cleaning... July 75 Tape vs. Disc Sound.... Feb. 75 Records: How High the Fi?...Nov. 72 Record Rating System... Nov. 72 Test Records... Jan. 75 ROOM ACOUSTICS Room Acoustics.... Mar. 73 Apr. 75 B.B.N. Concert-Hall Acoustics Simulator..Aug. 74 Sound TreatmentStudio & Control Rooms..Nov. 74 Room Resonance vs. Low-Frequency Response.. Mar. 74 Effects of Room on Sound... Apr. 74 May 74 TAPE RECORDERS

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Time and Turns Counter...July 75 Predistortor Modules...Dec. 75 Feb. 76 Reducing Distortion in Analog Recorders..Dec. 75 Braun TG1000.... June 73 Revox A77... June 73 Apr. 74 Aug. 74 Feb. 76....Sept. 75 Sony 377 Tandberg 9100X.... Sept. 75 Teac 3300.... June 73 Tape Clinic... Nov. 72 Dec. 72 Setting Up a Tape Recorder...Dec. 72 Oct. 73 Asperity-Noise Biasing....May 74 Hints for Live Recording... Nov. 72 Tape Saturation...June 73 How Magnetic Recording Works... July 73 Phase Lag When Recording...Sept. 75 Phase Error Cancellation...Sept. 75 Reducing Distortion...Dec. 75 A Note on Tape Recorder Clipping...Dec. 75 TELEVISION

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Rhoades TE-100 Teleadaptor.. Oct. 73 G.E. P4930A TV Audio Receiver..Dec. 73 Jan. 74 Advent Video Beam 1000 Color TV...Dec. 73 X-Rays and Your Color TV... Dec. 75
TONEARMS CM Modifying the AR Tonearm... Jan. 75 Mar. 75 May 75 Nov. 75 Experimenting With Decca International.. Jan. 75 ESS Tangential Tracking Tonearm...Feb. 76 Pioneer PL-61 Tonearm Damping... Feb. 76 Rabco SL-8E Damping... June 75 Sept. 75 Wooden Damping of SME Tonearm... Apr. 75 Transcriptors Vestigal Arm...Jan. 75 Mar. 75 Tonearm Damping for Optimum Performance.. Jan. 75 Feb. 75 May 75 Oct. 75 Nov.75 Checking Resonant Frequency...Oct. 75 TUNERS AC AC AC AC CM CM CM CM CM CM CM CM CM CM FM Null Switch...Apr. 73 Simple Multipath Indicator..Jan. 75 Multipath Distortion Detection... Feb. 75 Phase-Locked Loop Demodulator...Feb. 76 Citation XIV Tuner... Dec. 74 Feb.75 Citation XV Tuner... Sept. 75 Dehumming the Dynaco FM-5..Apr. 74 Kenwood 700T Tuner...Sept. 75 Kenwood KT-8007 Tuner...Sept. 75 Marantz 10B Tuner... Dec. 74 McIntosh MR67 Tuner... Sept. 75 McIntosh MR78 Tuner... Apr. 75 National Service FM Converter for Car.. Mar. 75 Pioneer TX-9100 Tuner... Oct. 73 Dec. 74 Apr. 75 Sequerra Tuner...May 75 July 75 Sept. 75 Sony 5130 Tuner... Dec. 74 FM Receivers for the Car.. Aug. 75 FM Tuner Overload...Nov. 73 SCA Interference: Cause & Cure...Dec. 74 TURNTABLES AC AC CM Micro-Seiki MSB-1 Micro Shock Absorbers..Jan. 76 Feb. 76 Discwasher D-Stat Record Mat... Feb. 76 Connoisseur BD-2... Apr. 74 May 74 Nov. 74 Dual 701....Jan. 75 Dual 1019....Mar. 75 Dual 1249.... Dec. 75 Rabco ST-4... Apr. 75 Technics 110A... Sept. 75 Turntables Tested... Nov. 10 2, 13 3,8 1, 9, 22 3-5,13 5, 6 5, 6

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VIDEO RECORDING CM CN Cartrivision... May 75 June 75 Video Recording for $150... Apr. 75 REVERBERATION CM CM CM CM CM Pioneer Reverberation Amplifier...Mar. 75 Experiments With Digital Time Delay...Apr, 75 Digital Audio Delay Equipment...Aug. 75 Echo-Verb II Spring Reverb... Nov. 75 Jan.76 Sound Concepts SD-50 Delay/Reverb System.. Feb. 76 PSYCHOACOUSTICS Psychoacoustics.... Feb. 74 Audiophilia....Mar. 73 Audible Phase Shift.... Feb. 74 Audible IM & HD.... Feb. 74 Double-Blind Testing of Audio Equipment..Sept. 74 Phase Shift Audibility... Oct. 74 Strategies for AB Listening Tests...Nov. 74 Feb. 75 Is T.I.M. Audible?.... Feb. 75 Apr. 75 Live vs. AB Testing.... Mar. 75 June 75 Aug. 75 Sept. 75 Oct. 75 Latest Model of the Human Ear...Sept. 75 Audibility of Phase Shifts... Sept. 75 Comparing Sound of Old & New Equipment.. Feb. 76 Epistemology.... Oct. 75 Jan. 76 Confessions of an Experimental Epistemologist.. Jan. 76 It ' s More Complex Than You Think...Jan. 76 MUSIC Temperment and Intonation... Dec. 73 Music and the Perception of Time... June 74 July 74 Control Over the Sound of Music...Aug. 75 Opera Recordings... Feb. 73 Musical School Recordings... Oct. 75 In Defense of the Piano... Aug. 74 MISCELLANEOUS Audio Library.... Nov. 72 Preventing Audio Equipment Thefts... Aug. 73 Audio Basics.... Sept. 73 Audio Shows.... Nov. 74 Finding Good 12AX7A Tubes...Dec. 74 Guide to BAS Speaker & Publications.. Dec. 74 Review of Book Audio Quality by G. Slot..Mar. 75 Why Audiophiles Can't Get Through the Maze..Apr. 75 Audio Magazine Addresses... June 75 BAS Membership Preferences... Feb. 76 What ' s Selling In & About the BAS... Feb. 8,10 7
Some Notes on Tonearms: Effective Mass and Seesaw Frequency Michael Riggs Effective Mass Doubtless the term "effective mass" seems cryptic to many audiophiles, for though it's often invoked to explain one tonearm's superiority to another, those invoking it seldom stop to explain what it means. That's unfortunate. The concept is not abstruse; in fact, its manifestations are commonplace, though the name unadorned, in the contexts in which it's usually applied, can mislead. An arm's effective mass is in part determined by the actual moving mass to which the stylus is attached, but the more important consideration is how that mass is distributed. As an illustration, let's imagine you're at a playground with a child. The child sits on one end of a seesaw. You stand behind him and lift or at the other end and push down. Now the child moves part way up the length of the plank toward the pivot, and you repeat the exercise. This time, however, the action requires much less effort. In fact, if the child sits halfway between the end and the seesaw pivot, the amount of force that must be applied to the end to move the seesaw through a given angle of rotation at a given angular acceleration will be only one quarter that necessary to move it through the same angle with the child sitting on the end. The effect in such a case is identical to that of replacing the child at the end with another of one-fourth his weight. The principle is that of the lever: by moving closer to the fulcrum, the child reduces his effective mass (or, perhaps more appropriately, his apparent mass). We can summarize by saying that the effective mass of a rotational system is that mass which, if it were concentrated in a single point at a distance equal to the length of the moment arm (from stylus to pivot, in the case of tonearms) from the pivot, would require the same force for the same acceleration as is required by the extended mass of the actual system. This follows from the relation F (force) = m (mass) x a (acceleration). Which tells us what? Mainly that the lower an arm's effective mass, the less work the stylus has to perform to push it around. This is a consequence of another well-known relation: W (work) = F (force) x x (distance). Obviously, then, we want the arm to weigh very little, and we want as much of that weight as possible concentrated near the pivot. Another way of looking at this is to observe that we want to optimize the length and the moment of inertia of the arm. That's because F = Ia/r 2 , where r is 2 the distance from stylus to pivot and I is the moment of inertia. Since F = ma, ma = Ia/r ; therefore, m = I/r 2. As we want a small value for m, the obvious solution would seem to be to make the arm very long. But that would tend to increase I by virtue of I = mr 2 , which says that each particle in a system contributes to that system's moment of inertia in direct proportion to its mass and to the square of its distance from the pivota tough engineering problem, and the reason why moving the child up the seesaw is more beneficial than putting him on a diet. The significance of effective mass is twofold. First, in an undamped arm it largely determines how close to the theoretically optimum tracking forcethe force required for proper operCopyright 1976 Michael Riggs

pillar. Care must be taken not to turn this too tight, stripping the plastic threads, and at the same time to move the fixed insert for the bias thread at the edge of the dome toward the rear and laterally. That way the thread will engage the groove in the dome that is in the same horizontal plane as the tip of the steel pivot needle. When that is done, the arm is lowered into place, with the steel needle resting in the sapphire concavity, surrounded by silicone. The thread is placed over a miniature bias bearing and adjusted so that the thread is horizontal. Vertical balance is simply a matter of moving the counterweight backward or forward. Lateral balance, which may require three hands, is accomplished by rotating the eccentric counterweight until the alloy hub of the arm is parallel with the arm base. Bias is adjusted by adding calibrated metal discs to the bias weight holder, but fine adjustment, they say, may require the use of a test record. The best I could do was adjust for no lateral drift on a blank portion of the record. The hydraulic lift on the base is adjustable laterally and vertically and is very smooth in operation. An alignment protractor for tracking error is supplied, and adjustment for this is made by moving the cartridge backward or forward in the nondetachable skeletal head shell, which also rotates on axis for vertical stylus alignment. Tracking force is set by means of a sliding cursor on the arm, calibrated in 0.1-gram intervals up to 3 grams. They claim a nominal effective mass of 4.5 grams. (Can anyone verify this?) After all this, how have things changed? Quite unlike the Stanton previously, the sound is very smooth and extended at the top. Sibilants are much softer and more natural, and the bass, especially the low bass, is very solid and clean. Sound imaging is dramatically precise, and warp wow is virtually absent, except on severely warped records with, interestingly enough, less stylus motion than with the Vestigal. I have several minor quibbles. 1) The arm drifts outward about 2 mm when placed on the raised cueing device prior to lowering the arm because of delayed vertical equilibration around the pivot from viscous damping. So one either waits till it stops in 2 to 3 seconds, overcompensates, or moves the arm much more slowly. 2) The eccentric counterweight, with its offcenter hole is not easy to adjust for vertical equilibrium. A tight screw totally immobilizes the rotation of the counterweight, but a slightly loose screw results in the heaviest side of the weight in the dependent position quite rapidly. Fine intermediate adjustments can be difficult, so an extra pair of hands is helpful. A two-part counterweight, with a center that could be tightened after the vertical balance was complete and a concentric outer portion on a fine ratchet to make the lateral adjustment, is a thought. 3) The Transcriptors dust cover no longer fits, because of the rear overhang of the arm. This, however, would probably not be a problem with most turntables. Perhaps the sound is different in part because of a lead capacitance change, perhaps because of arm-cartridge resonance differences, or maybe as a result of damping of spurious oscillations. Most likely it is a combination of the three and possibly other unknown variables. In any case, if warp wow gets to you as it has gotten to me, and your local record outlets do not have a separate bin for flat records, this arm may be the most economical way to salvage your sanity. My Vestigal awaits a renaissance in flatness. The Formula 4 is a very nicely finished product, but only time and usage will determine its durability. Has anyone tried these viscous damped arms with silicone of different viscosity? Has anyone used one of the Formula 4 cartridges?

The Formula 4 PLS 4/D Tonearm -- II Dow O. Williams
The instruction manual for the Formula 4 is clear and unambiguous but barely adequate for a first-time tonearm installer. It is far easier to install and to adjust than the Decca International, which it has replaced. Mounting a cartridge in the nondetachable headshell is, however, a test of patience and dexterity. No matter what the instructions say, affix cartridge to headshell first , then slide on the connections. Rotation of the head shell for vertical stylus alignment is accomplished by loosening a small screw in the head shell collar. The screw is underneath, for cosmetic reasons, I'm sure. It would be far more convenient on top. However, once the arm itself is leveled and the headshell rotated for vertical stylus alignment, there shouldn't be any further need for headshell alignment. When set up in static balance, my sample has a very slight lead drag pulling the arm back toward the arm rest. This is a smooth, gentle pull with no consequence, except maybe to reduce the amount of bias compensation needed for perfect stylus/wall contact. This bias correction is of the thread-and-weight kind, but unique in that it applies torque in the exact plane of the unipivot and is exactly the same from beginning to end of arm swing. A number of small weights are supplied so that proper bias can be achieved with any tracking force up to 3.5 grams. The cueing lever feels a bit rough and stiff but would probably smooth out in use. I simply removed the mechanism and used a Decca Lift instead. (This device is worth its weight in gold. See review by Holt in The Stereophile , No. 2, 1968.) Phono cables connect to the arm base with a special plug molded onto the cables, making it impossible to use one's own low-capacitance cables, as I had hoped to do. I did reduce the length by 18 inches and replace the RCA plugs. The original length is 4.5 feet, with a total capacitance of 112 pF. I accidentally set the stylus force at 1/2 gram instead of 1 gram and noticed the error only upon rechecking. This suggests that the tracking force of some pickups might be reduced without sonic deterioration. Viscous damping is ingeniously applied and probably can be adjusted to optimum by adding more or less silicone fluid to the cup (see BAS Speaker , Oct. 1975). There is enough fluid included to permit experimentation. Warps and ripples cause little stylus bar flexing or headshell bouncethe entire arm rides the undulations easily. Warp wow is no more noticeable than with the Decca, although the unipivot is in a plane well above the record surface (about 3/4 inch). Sonic improvements are subtle but definite: The "aether" is cleared up, reducing listening fatigue; image stability is improved; lows go lower and cleaner; stereo spread seems more consistent. There is more to this arm than immediate sonic improvementit is a pleasure to use, and the simple but elegant design and sturdy construction evoke confidence.

Copyright 1976 Steven L. Seto and Nate Garfinkle
This brings up another characteristic, namely the problem of decay time. The 1000 appears to use virtually instantaneous decay of the peak-boosting action; as soon as the signal level of the source declines, the peak unlimiter immediately reduces the gain. It's easy to see why this approach was taken; this way only the signal peak that caused peak unlimiting is affected, and adjacent lower signal peaks are not disturbed. Of course, that's also the problem. Every instrument has a characteristic decay which our ears learn to associate with that instrument. Thus, when a loud note is produced, there is always a certain way in which the note must decay away in amplitudebut the peak unlimiter manipulates amplitude (gain) in a nearly instantaneous fashion; thus the effect is rather unnatural. Fortunately, the ear, as well as being critical, can also be somewhat forgiving, so that the audible effect is not always as bad as I've made it appear. As with the autocorrelator, it depends on exactly what sort of music you're playing. One other problem with the 1000 seems to be reliability. Although parts and construction quality of the 1000 are above average, my unit has had and continues to have problems. Two visits to Phase Linear service have not completely corrected the situation, and although I have no doubt that the unit is working correctly electronically, it still has some mechanical problems, namely an intermittent left channel caused by a faulty tape monitor switch. This despite replacement of the switch by the local service station and another inspection at the factory service center in Washington. I have the impression from talking with the servicemen that the switch strip has been giving them some problems. So what conclusion can be drawn from all of this? It seems that overall, the Phase Linear 1000 can be a useful addition to most systems if you understand, and can live with, its idiosyncrasies. It is my opinion that the peak unlimiter works better than the dbx 119, and the autocorrelator works well regardless. After that it's up to you. [Ed. Note: Robert Carver of Phase Linear, in a recent appearance on WBUR's "Shop Talk" program, stated that recent versions of the 1000 are significantly improved over the earlier versions.]
The Quad 405 Current Dumping Amplifier Nate Garfinkle
The Quad 405 is a 100-watt/channel (into 8 ohms) power amplifier that uses a current dumping output circuit, a Quad invention claimed by the manufacturer to eliminate many of the problems associated with transistor amplifiers. In a current dumping amplifier, there is, in effect, both a low-power, very high-quality amplifier and a high-power, heavy-duty amplifier. The low-power amp controls the signal at all times, calling upon the high-power section to provide most of the current. The small amplifier is so arranged (it carries an error signal) that provided the larger power transistors get within the target area of the required output current, it will fill in the remainder accurately. Reproduction quality is thus solely dependent upon the small amplifier, which, because of its low power, can be very good. The results are that problems of crossover distortion, quiescent current adjustment, thermal tracking, and transistor matching all disappear. I received two 405's in late January, to replace my Quad 303 amplifiers, which had been in service since 1968. I installed the power limiter in one, so it could be used to drive my Quad ESL's. The other is used full power to drive a pair of transmission line infrawoofers below 65 Hz. (This system is described in Hi-Fi News , July 1969 and Jan. 1972, and in Audio , March 1970.)