Dear Editor (Sept. 1977)

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Audiophile's Renaissance

Dear Sir:

As an inveterate hobbyist, I am returning to the field of high fidelity after a lapse of many years. My first thought was to dash out and secure the current issue of Audio, which, for my money, is the most authoritative publication in the field.

After having done such, I was amazed at the gimmickry available in the audio field today. My own beginnings were with a Stromberg-Carlson amplifier and turntable. There were no speakers available as there are today, so I built my own enclosures using an Altec design and Wharfedale raw speakers.

One of the finest audio systems I ever heard was a Gates broadcast transcription turntable, a standard tonearm with a Grado cartridge, McIntosh amplification, and Bozak corner enclosures. The sound reproduction was unbelievable.

The program sources have certainly deteriorated. In the beginning certain companies, such as Command Records, took great pains in constructing the original source using 35 mm tape and quality pressings. The original Muzak with its vertical groove was fantastic but, of course, it was impractical with stereo.

Tube or not to -be, in my opinion, there is no argument of the reserve power and drive and the fullness of sound in tube drive. Certainly solid state is in vogue and will continue to be, but it has a thinness and transparency to it. But, solid-state units are reliable and compact with no heat problems, so they have much going for them.

Of course, beauty is in the eye of the beholder. In photography you do not need a Hasselblad to take pictures of your Uncle Fred waving to you with a can of beer, nor do you need a $5000.00 sound system to play the "Funky Donkeys" whose tonal range goes from 13 to 15 kHz.

I have been engaged with sound systems for nearly all of my working life, mostly with motion picture sound equipment, along with broadcasting experience with KMYR-FM and KFML in Denver Colo.

Henry LeClair San Diego, Cal.

Pollution Pragmatics

Dear Sir:

In looking back over the Annual Equipment Directory which appeared in the October 1976 issue of Audio, I was fascinated by the impressive specs of the "Rabid Audiophile Bazoom 2000 Amplifier" listed on page 46. My only question is: will it pass the California emission control standards?

Walter Argus Albertville, Ala., USA

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Percy Wilson

Percy Wilson, aged 84, died April 30th at his home in Oxford, England.

During the 1930s he was one of the pioneers in improving the quality of electrically reproduced sound, and he was also an expert in the field of sound recording. His interest in the audio field began in 1923 when he joined the staff of the newly formed The Gramophone magazine where he served in the capacity of technical advisor from 1924 to 1938 and technical editor from 1953 until 1966.

In 1966 he was the second Briton to receive the Audio Engineering Society annual citation in recognition for his technical contributions to the problems of stylus alignment, horn speakers, and record cleaning. He was past president of the British branch of the AES when he became a Fellow in 1970 and an honorary member in 1972.

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Tuner Lineage

Dear Sir:

I am a long time subscriber to Audio magazine and am wondering whether you can help me or at least direct me to some organization that can. About 12 years ago a friend of mine gave me a tuner, and I would like to find out some information about it before attempting to use it.

The name on the tuner is "Trans wave" Model TW-102. There is only a power on/off switch with no volume control. The mode is FM/MPX, with an on/off filter and an AFC control.

The rear of the chassis is a "level set FM" with one outlet and connections for antenna and tape output. Inside the chassis I can see part of the flywheel with the logo "Star Company Ltd." stamped on the metal. The tubes are Hitachi and other Star products.

I would greatly appreciate your assistance in helping me find out about this tuner.

Joseph Ruivo New York, N.Y.

Leach Preamp Addenda

Dear Sir:

I hate to burden you with another preamplifier addition, however many people are writing me about a hiss problem that they are having.

It turns out that some zener diodes are noisier than others, so much so that I couldn't believe the hiss in the preamplifier I was sent. In my unit, used two 12 -volt zener diodes in series for each of the 24 -volt units that I specified in the article. There were no noise problems with these. Since the problem has developed, I have worked up the regulated power supply shown on the enclosure, and will send copies to people who write me about this problem. For every person who writes or calls me, I am sure there are many more who encountered the problem and never solved it. Audio magazine is the only way that I can communicate with them. I only wish that these problems would show up in the design stages.

Due to excessive noise caused by the zener diode regulators D1 -D4 in the wideband preamplifier, the regulated power supply shown here has been developed. This circuit also eliminates all turn -on thump. The power transformer should be the one originally specified, or one rated at 52 to 55 volts center tapped. To use this regulator, remove D1 -D4 from the circuit boards and change the value of R31 -R34 to 22 ohms, 1/8 watt. C11-C14 should remain at their original values, as should C15 -C18. The additional component values are: R46 & R47, 120 ohm, 1/2 watt; R48 & R49, 1.8 kilohm, 1/2 watt; C22 & C23, 100 µF, 50 volts; D1 & D2, 24 volt zener diodes, 1 watt; Q11 2N2102, and Q12 2N4036.

Both transistors should have finned heat sinks installed on them. Three prong plugs and jacks should be used for the interconnecting power cable instead of phone plugs and jacks, for Q11 and Q12 will be blown if the latter are used when the plugs are inserted or removed from the jacks. The complete regulator can be mounted on a 7 -pin terminal strip, with the center pin grounded.

In case anyone who built the circuit didn't see my letter in the April issue of Audio magazine, I would like to correct a component value error that was published in the February article.

The correct value for R3 in the RIAA circuit is 39 ohms, and not the published value of 390 ohms. The incorrect value will cause the circuit to be susceptible to r.f. oscillations. Do not use it by mistake. Builders of the low TIM power amplifier should use 1N4934 diodes for D6 and D7 in the protection circuit. These very low capacitance diodes will improve the operation of the VI limiter.

W. Marshall Leach, Georgia Inst. of Tech. Atlanta, Ga., USA


ALL INDICATED COMPONENTS SHOULD BE MOUNTED ON THE POWER SUPPLY CHASSIS

(Source: Audio magazine, Sept. 1977)

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