John Curl's Blowtorch preamplifier part II

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Also, design and preparation of manufacturing is long and costly process. If say design and preparation of manufacturing costs one million dollars, it's part in the party of million devices will be 1 dollar only. For party of 100 peaces there would be 10,000 dollars per peace. That means design and preparation of manufacturing capable to produce and sell one million of devices is not needed, but manufacturing itself anyway is more costly per peace of equipment. So, if say the device will cost 9,000 dollars we can add 1,000 dollars on jewelry, as the result consumers will like it more, and probably market will be wider.
 
The most intellectually 'perfect' speaker design that I have been exposed to is the Manger.
Yet, I was never fully happy with its sound. Again, just because the theory is wonderful, doesn't mean that it will sound wonderful. That is why we use our ears to evaluate.
One of the most consistent speakers that most people remember from first listening might be the Klipschorn. Dave Wilson, Mark Levinson, Richard Heyser, and I, found it intriguing for a period of time, for example.
 
As this is still the Blowtorch thread, I would like to openly state our original purposes for the CTC Blowtorch, in case anyone doesn't fully know them.
We fundamentally wanted a preamp as sonically perfect as possible. A personal preamp for ourselves. However, in order to make the time and trouble to design and build a few units worthwhile, we also wanted some other people to buy one too, so that we could spread out the effort, make reasonably large purchases, you know: 100 for small parts and 5 or so for the larger parts, in order to get a reasonable discount. It doesn't take 1 million dollars to do this, BUT it does cost many thousands, that you start to get back, once you sell a few units. One's time should not be FREE when you do a service for a number of other people, as well, most you will never meet, and this also adds to the cost per unit.
Now I realize that some people think that you can throw a few IC's together with some cost effective resistors and capacitors, and get 'audio nirvana' or at least something that will pass a double blind test, kind of like '2 buck Chuck' as a decent bottle of wine.
However, being around this audio business for decades, and living with a lot of audio equipment, we knew that just about everything we used was 'flawed' in some way. I mean, I have developed perhaps a dozen audio preamps, and when we started, I was happy with a multi-turn pot as a volume control with some connectors on it, for a preamp, and everything else put in the closet. Could we, for example, actually make something as good or better than just a single component for a preamp? This was the challenge: How can we have input switching, some voltage gain, some output drive, and balanced out, if possible, even if the inputs were single ended? (more later)
 
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My friend and business partner, Bob Crump, one of the C's in CTC, had a sense of humor and an extensive set of audio contacts. I could NEVER have found enough people interested in this sort of project, to make it possible.
Part of his sense of humor is to OUTDO most of the competition. We would make the heaviest, most exotic preamp possible, with BIG KNOBS.
In fact, our prototype, had even bigger KNOBS than you have seen in photos. I called them Dolly KNOBS, and I said, Marilyn Monroe KNOBS would be more appropriate, as the Dolly KNOBS made the preamp look like it was going to tip over.
We did not want to just use sheet metal, been there, had done that, and it always seemed to vibrate somewhat, being so thin, and the screws often got loose, so Bob tried to find somebody to weld an aluminum chassis together. We found somebody, but apparently he often had a bottle of beer in his hand, when welding the chassis together, and we could not be sure of consistent results in future, so we changed to 'hogging out' a billet of aircraft grade aluminum which eliminated any 'seams' to worry about. Neither approach was cheap, but for about $1500, we could get a couple of aluminum cases, which we then had to find somebody to add the outside labels that would look good, and not wear off. No 'stick-on labels' for us! People, who have never tried to do something like this, often think we were crazy or were 'cheated' by the machinists, but I have tried others, and we get the same price, more or less. We knew that the fit and finish had to be 'perfect' to get the kind of customer who would buy our product. It didn't matter that much to us, personally, but we often had to show our own personal units to potential customers, reviewers, and to take to CES, so our personal units had to be 'perfect' too!
Now don't think that the effort that we made to produce this chassis was completely for looks. It was functional too! First, being aluminum, it did NOT add to any potential problem of using steel. Second, being THICK aluminum, it became an effective shield all the way down to hum frequencies, and really good above a few hundred Hz. Third, it did not 'ding', it went more like 'dunk' when vibrationally excited. Fourth, it is a very sturdy case, that you can mount heavy duty switches and pots to, without stressing the case. Fifth, the interior is virtually dust tight, keeping stuff from getting in the chassis to either tarnish the switches, or dust to accumulate. Etc. (more later)
 
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formula for real C's --

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While we are waiting for JC to come back -- has anyone ever seen the 'real' Z formula for a Cap with its parasitics? Or ESR of a 'real' capacitor?
[Exerpt from white paper I wrote a million years ago.] -RNM
 

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Yes, it does. It also sounds very over-sized. Everything is bigger than life. That has a certain charm for awhile. Then cellos the size of a Mack truck might start to bother you. :) Amazing detail, tho.

Large speaker systems - with drivers spread out over large area do not act like point sources until you are listening much further back from them. Then they start to 'focus' better.
 
In my design experience, I have used a number of approaches to design selection switching in preamps.
For 10 years, I lived with the wafer switches in the Dyna preamp. Over the years, I could see that these switches tarnished, but, oh well.
Then Mark Levinson gave me a JC-2 preamp with military grade rotary switches. The whole preamp was a step up, being quieter, lower distortion, etc. The switches were somewhat 'sealed' and that was probably a good thing.
Years later, I started to use sealed relays for switching. We used these for the JC-80 with some success. Relays gave us an improvement of Xtalk, reduction in actual wiring, and a lot of flexibility. We still used rotary switches for control, but they only controlled DC rather than audio. Worked fairly well. Never lost a relay.
Next, I designed a preamp for Lineage, a startup company with Saul Marantz as president. They thought mechanical relays were too expensive, so I started researching cmos and jfet relays. I still have many dozens of samples. They worked fairly well, and we made a few decent preamp prototypes. We could get the distortion low, but not unmeasurable. Sound was OK, but I think that relays still held the edge, and I continued to use my JC-80 for about 10 years.
After a succession of Parasound preamps, starting with cmos selector switches, etc, we finally wound up with relays, just like the JC-80, and Parasound still uses them today in the Para. JC-2.
Still, for the CTC Blowtorch, Bob insisted on Shallco silver on silver switches. They are BIG, hard to turn, but do they work well! Now the big knobs have a real advantage in that they provide the torque to easily rotate them. Nice to know that they do something extra well. The only 'improvement' that I can recommend over the Shallco silver switches would be NO SWITCH at all. This is very inconvenient, but it DOES work.
We needed SOME convenience, especially for our customers, so Shallco switches it was. That is one of the reasons the CTC box is so large. There are other reasons as well. (more later)
 
In any case the Blowtorch used Shallco switches and they do a wonderful job, even if they are limited in their versatility. So long as we don't ask too much of these switches, they can be considered almost perfect.
However there is a 'downside' to using these switches, as well. They REQUIRE that you wire up to them, rather than access them directly from a circuit board. In one way that is better, because AIR is a better dielectric than most plastics or whatever circuit boards are necessarily made of. The problem is then: What wire do we use that will not have any significant 'downside'?
Well, Bob Crump found a certain silver wire, made by some rather small company, to be the best hookup wire that he ever worked with, and as he made cables on the side, he had plenty of experience with many different types of wire. This wire was almost prohibitively expensive, and we had to buy a lot of it, on a roll, for many hundreds of dollars, to get it at all. I was very worried about using silver wire, at first. I had had bad luck with silver wire. It typically sounded very BRIGHT, and that 'brightness' could be heard by others, even if they did not know what the wire was composed of. Over time, however, this brightness seemed to fade, at least in my limited experience.
Bob knew about this 'brightness' and he found that 'breaking-in' or running audio signal through the wire for perhaps 30 days, even while it was still on the roll, would take the 'edge' off. So we broke-in our wire, in advance, before cutting it and soldering it in the chassis.
Now, I know that many of you do NOT believe in break-in. No matter, it worked for Bob, and I was also happy with the results. MY preamp sounds clear, without 'edge'. Copper wire versions of the Blowtorch that I personally made without silver wire, but the best copper connecting wire that I could find, sounded 'softer' overall. Not quite as 'transparent', as the all silver version. I did a direct A-B test in my own living room. However, it would be difficult to chose which was really better, IF the rest of your audio system was not up to an equal standard. The copper wire might be actually better, overall, in a more typical domestic playback system. The silver wire was perhaps just too 'revealing', and not as 'forgiving' as the copper wire.
 
Yes, it does. It also sounds very over-sized. Everything is bigger than life. That has a certain charm for awhile. Then cellos the size of a Mack truck might start to bother you. :) Amazing detail, tho.

I heard the "single" version. Images were VERY realistically scaled and as you know, I'm an imaging freak. Still just about the only commercial speaker I've lusted after.
 
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