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  #1  
Old 02-13-2008, 02:41 PM
bartonn bartonn is offline
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interesting post from the designer of the CMA-10-2dl - Wayne Chou

from:

http://forum.stereophile.com/forum/s...0&fpart=2&vc=1


I read with interest the review on Rudy Bozak’s Concert Grands in the October 2005 issue. I had no idea that so many audiophiles where still tracking some of the vintage equipment – I had left the business sometime in the later part of the ‘60s. The only reason I came across this forum was because it was time for me to find a home for my own two Concert Grands which were given to me by Rudy in the mid 60’s (I am not aware of the magnet change later, but these must be alincos). And naturally, my pair would have been the first to have been bi-amp’d – but I still have the original crossovers, if someone would want to put it back the way it came. After that, Rudy finally offered bi-amp versions for sale.

I was co-founder and president of C/M Laboratories, Inc., (a contraction of the names Chou and Morris) and I had invented, and eventually patented, an output power transistor circuit that was impervious (for the most part – nothing is perfect) to short circuits and other transients (mostly from the bass of music – and if you like Bozaks, you were sure to pass a lot of heavy bass just to feel it in your body). Technically, power transistors were susceptible to a phenomenon known as “secondary breakdown”. Later RCA pirated the circuit and marketed it in a hybrid chip. And HH Scott, published a paper about how his amplifiers would not blow up (describing my invention without giving me credit or my permission to do so, either). Since I was very enthusiastic about sound reproduction, this circuit found its way into our first power amplifier, the 35D, which produced conservatively 50 watts rms/channel, with very low distortion, for its day. In developing the amplifier, I sought Rudy’s help – borrowing loudspeakers from him, as well as exchanging amplifiers for speakers when we went to shows and exhibits. Rudy and I became good friends. Through the four or five years that I was president, I had designed many amplifiers, pre-amplifiers, as well as combined units both for the consumer market as well as for the professional sound reinforcement and recording studio monitor market. I should add, that while Rudy designed the front panel of the CMA-10-2DL, and specified all the features he wanted in it, it was I who designed all the electronics for it, and it was C/M Labs who built it for him, hence the designation CMA. But he did supply the panels and the punched out chassis, as we specified it.

Though Rudy’s speakers were known mostly by the audiophiles in the consumer market, by the time I got to know him, most of his speaker designs had not changed – only, more or less, cosmetically. Most of the joint effort that we spent our time on was in promoting his commercial line of column speakers as well as helping him get started in the amplification end of things. We did joint projects – his speakers, along with our rack mounted amplifiers and pre-amp/mixers, at Lewison Stadium, West Point, SUNY, the New York Philharmonic trailer in Sheep Meadow at Central Park, various benefits with Benny Goodman, and so forth. It was the experience of a lifetime I will never forget. Although Rudy Bozak could be tough in business, he was a kind, gentle, and generous man. I will forever miss him.

I am still thinking of finding a home for my Concert Grands. So if anyone wants a pair, or knows of someone who wants them, please let me know. The first home I had for them sat them in a room 30 x 40 with a 12 foot high plaster ceiling. It is true – that they need the space for one to be able to appreciate their voice. They are currently being driven by my 35D for the mid and upper end, and a 911 (100 watts/channel) for the woofers, using a C/M Labs switch adjustable electronic crossover (of which very few were made – bi amping was not too popular, or well known, at the time). Still, after 40 years, I haven’t found a system I like better. Stood the test of time. But of course, my hearing isn’t what it used to be. Still, I get that great concert hall sound from the Concert Grands, never favoring one instrument over another, or making anything sound exaggerated or unnatural. The bass is tight, as it was too boomy and sloppy being driven by the usual tube amp. But it is not a matter of whether driven by tubes or transistors, as most non-technical people would try to romanticize the reasons, but rather by design of what is practical when using tubes or transistors. It just is easier to design an amplifier having output impedances where they are naturally there to begin with. Damping factor is the primary reason why transistors have that edge on controlling the loudspeaker, circuit-wise. Years ago I presented a paper on the importance of damping factor, and how it affects sound quality. Rudy and I proved that to ourselves through the many listening tests we made together. That was an exciting time for us. Eventually, he used our amplifiers exclusively for his own personal use and demonstrations, setting his McIntosh amplifiers in storage. Today, everyone realizes that using heavy speaker cable will improve audible definition over using thin hookup wire. You cannot fake physics.

As a final note, C/M Laboratories, Inc. went the way of most everything – it was sold off to other investors who carried the line for a few years after the acquisition. We enjoyed a reputation up with Marantz and McIntosh, but the Japanese imports were hot after US business. They had better finished panels, better control feel, all around better styling. The only thing that they didn’t have at the time, was the ability to reproduce audio at the highest level. But they were close, and catching up. At the same time, I was concentrating on developing a new FM tuner – I was warned that it would probably break us. And it did. But what a tuner. We had 25 orders from a show at $1095 (retail) a pop – FM tuner only, no preamp, no power amp. But it was the first consumer programmable digital readout (Nixie tubes) tuner, that did not require tuning (a crystal controlled synthesizer – unheard of in a consumer product, in those days), all solid state circuitry, linear phase bandpass filters, and a new all solid state linear detector (no discriminator to add harmonic distortion) – all specs (capture ratio, stereo separation, distortion, selectivity, 3rd order intercept, etc.) to exceed anything else on the market then including the famed Marantz 10b, the target to beat. The prototype/breadboard had been tested by a couple of reviewers, so we knew we were on the right track. Unfortunately, we couldn’t fit it all in a reasonably sized box (of all things), and production delays of all sorts kept delivery from coming to fruition. It was the closing bell to C/M Labs as we knew it. Thanks for listening.

Wayne Chou
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  #2  
Old 02-13-2008, 03:18 PM
Vman Vman is offline
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I read this post a few years back when I first got a bozak.....cool info on collaboration and design with him and Rudy.


Peep this article:

[url="http://www.americanheritage.com/articles/magazine/it/2003/3/2003_3_4_print.shtml"]LETTERS

THE GREAT TUBE DEBATE
Distortions about distortion?

I LOOK FORWARD TO READing Invention & Technology, but when I openec the most recent issue, I knew I’d be in trouble. I agree with guitarists that tube-sound distortion is what they’re after (“The Tube Is Dead. Long Live the Tube,” by Mark Wolverton, Fall 2002), but I wince when people say they prefer tube sound over solid state when it concerns the reproduction, not production, of music. In almost any music the dynamic range is so large that a signal may occasionally get clipped in an amplifier, but in a properly designed amplifier, transistor or tube, the signal gets into and out of clipping practically inaudibly. If the sound is terrible, it is the fault of the user. Get a larger amplifier or turr down the sound.

I get particularly annoyed when people begin to romanticize about the glow, warmth, ether, magic, and sc on of the vacuum tube. Thai is absolute hogwash. There is no scientific basis for the belief that one is inherently better than the other.

The trouble is that manufacturers test for the simple stuff—distortion, power, and frequency response—and certain manufacturers’ consortium guidelines tend to give everyone high marks. There’s a lot more going on. For one thing, a tube is a high-impedance device, and a transistor is a low-impedance device. When tubes are used, a transformer is usually needed to match them to the load. That’s because when the voltage to a loudspeaker stops, the loudspeaker should stop, but it doesn’t, because the speaker has mass, and so a voltage is generated back on the speaker wires, which is, in effect, amplitude distortion. Low output impedance (also known as high damping factor) causes the speaker to react to the amplified signal and not to its own inertia. Therefore, solid-state amplifiers tend to sound tighter, particularly in the bass region, where the speaker is more resonant and harder to control. This is also why “monster” cables help, because they continue the low impedance from the amplifier to the speaker.

If you want a tube-type sound, you can easily emulate it by hooking up thin wire between your transistoi amplifier and your speaker, thereby reducing the damping factor. If you like a boom-box, muddy jukebox sound, go for it. You’ll save a lot of time and money try- ing to locate a working vintage tube amplifier.

Wayne E. Chou
FOUNDER AND FORMER CEO
C/M LABORATORIES
RIDGEFIELD, CONN.


Is Wayne still around/alive? It would be cool to contact him and have conversations about sound systems on this board. Mario or Scott any contact info??


v
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  #3  
Old 02-13-2008, 04:21 PM
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mynameismatt mynameismatt is offline
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That would be great!!

There's an email address for Wayne at the bottom of this page. Someone who knows more about Bozak should send him an invite.

http://64.233.169.104/search?q=cache...k&c d=4&gl=us
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  #4  
Old 02-13-2008, 11:39 PM
clubman5 clubman5 is offline
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I remember CM Labs. I DJ,ed on a cruise ship for 3 months, The Scandinavian Sun, out of Miami, to Freeport every day, in 1983. Weekends were hot, sexy singles going to Bahammas to gamble, I played cool music in the ships club, and I had MORE pussy in those 3 months EVERY NIGHT.

We had a CM Labs mixer in that club, and my first night on board I saw this thing and said whats that? The ships entertsinment director told me it was were you played the records from. Me being me, I asked, O you have aBozak mixer instead? She said what the hell is a Bozak? So, Im tellinmg her what a Bozak is, and she said, Oh, I thought it was more like body part or something. Then she said come have a drink later with me when the ship docks.

GREAT start, and The CM Labs mixer sounded good too. Shit, as many women as I had in those 3 months, AM radios sounded great..

And EVERY afternoon, in Freeport we always headed straight to Sir Winston Churchils Pub, for the BEST Conch Fritters anywhere, and black and tans!

21yr old single male, on a party ship loaded with partying singles, every night, playing music, the pay was pretty good, the fringe benefits were even better. I didnt need money then!

Matter of fact, I would have worked for free, THE BEST TIMES!
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  #5  
Old 02-14-2008, 08:37 AM
thermionic thermionic is offline
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Wayne is a fascinating and talented engineer (I have exchanged several emails with him), as well as a nice guy. I have been compiling an interview with him, which is quite advanced, but unfinished as commitments intruded on both our behalves.

Unfortunately, it transpires that he was involved in designing the original CMA-10 mixers, not the D and DL-onwards mixers.

Wayne is well worth speaking to if you get a chance, as he's an engineer par-excellence and general audio connoisseur, but the post about him designing the 2-DL is due to the fact that he worked for the company many decades ago and confused the DL with the PA / Recording mixer which preceded it - the original CMA-10.


Justin
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Bozak CMA 10-2-DL Full Rebuild

How Mixer Level Controls Work

Important Differences Between Types of Bozak

Last edited by thermionic : 02-14-2008 at 03:32 PM.
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  #6  
Old 02-14-2008, 10:18 AM
bartonn bartonn is offline
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Was it still C/M Labs that did the DL versions as well, or had it moved in house into Bozak by then?
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  #7  
Old 02-14-2008, 03:24 PM
thermionic thermionic is offline
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From the emails I have exchanged with Wayne, I am 99.9% sure that he - and CM Labs - had nothing whatsover to do with the DJ mixers, i.e. the mixers that came after the CMA-10 mixers (which I believe were originally designed at the request of classical orchestras, who wanted a high quality rackmount mixer).

I emailed Wayne earlier, and this is his response:

Quote:
Question: Did CM Labs continue to subcontract manufacturing for Bozak after you sold the company? Do you know which lines they took on if so? Did CM Labs ever market its own mixer that was unconnected with Bozak?

Wayne replied:
Quote:
When I sold the company, C/M Labs was already doing custom work outside of the normal high fidelity/sound reinforcement business. For one thing the Japanese imports such a Pioneer, Kenwood, etc, were taking business away from the would be buyer of higher end equipment. So we designed and made custom consoles for AT&T, visual and sound control rack for universities like SUNY, West Point, etc. The people who bought C/M were interested in developing the telephone and solid state switch business, and so their interest in Bozak was probably minimal. When I was there, Rudy and I had a close working relationship. So if he wanted any changes, I could easily comply and create a new design, which I am sure stopped after I left. He was forced to develop his own talent.

For the same reason, there was no reason to design our own mixer, since the only real connection C/M had to the commercial market was through Rudy.

Wayne is a mine of information. The plan is to publish a full interview at some point, possibly when he has some new hardware coming out - he deserves the publicity. Not only did he work closely with Rudy Bozak, but he also got to know Saul Marantz...that's quite something! His admiration for Bozak and Marantz is quite apparent, and he has some fascinating observations from the time.

Justin
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Please note that this account is dormant for the time being. I apologise to all that have sent PMs - there are just not enough hours in the day!

Bozak CMA 10-2-DL Full Rebuild

How Mixer Level Controls Work

Important Differences Between Types of Bozak

Last edited by thermionic : 02-14-2008 at 03:33 PM.
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