John Curl's Blowtorch preamplifier part II

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A small aside: My future wife, a young violin student was late for her master class with Zino Franciscatti and was in the elevator with an older lady, who happened to be the sponsor of the institute she was attending. Apparently, being late, she was nervous, and kept muttering Sh--, Sh--, Sh-- to herself. Overhearing, the mature and stately benefactor corrected her, saying: 'No dear, it's Merde'. ;-)
 
Uh, oh. I'm on the police radar now :)

Je ne comprende pas Jacques Merde.

While we are on how things translate why is it that no one can translate "je ne sais pas?"

:)

I am going a bit crazy as today is being spent build RCA stereo to mono adapter boxes! Used to be a Y cord was fine, then RDL made an STD-10K combiner, so all of the large projects call for it to be used. As these are $40+ I build a small metal box, mount 3 RCA jacks (cosmetic gold plated) and wire two resistors. As the jacks cost me 19 cents, the resistors a penny and I can make boxes for 75 cents a pound, the two dozen I need justify my waste of time.

That is because the design professionals judge the sound system with their eyes. A metal box combiner is bigger and must be better than a plastic box, which must be better than a Y cord.

The other issue that keeps getting missed is we prefer to hear what we expect. Way back I remember when Scully tape decks were all the rage. They replaced the older Ampex 350's. The Scullys were modern and solid state. They even had an optional distortion canceler circuit to compensate for magnetic tape saturation.

I remember listening to a record one time and noticing the Scully sound on it. Checking the liner turns out I was right, it was recorded on a Scully. (Sy not sure, is this an accurate test?)

Of course if you were to put a good working condition Ampex up against the equivalent Scully, I suspect virtually everyone would pick the Ampex as better sounding.

But in the day Ampexs got dumped wholesale, today they are still treasured.

So when someone tells me they like the sound of carbon composition resistors, or some such, they really aren't wrong. But I would not let them guide me.

So John it is possible that the golden ear reviewers prefer the sound of discrete components over I.C.s.

Of course on the other hand some people considered cables to sound better sending signal one way than the other. Absolute nonsense, I thought, surprised me so much I (Can't mention the physical reaction here Jacques) when I found I was able to measure a difference. Yes it was a ridiculously small difference. So were the golden ears right or was it coincidence?

Of course there is a small power amplifier we keep around here that has 5-10% 2nd order harmonic distortion at full power. It is interesting to demo it to people and compare it to a popular model that is RATED less than .05% at all levels. Virtually everyone prefers the higher distortion one.

Oh yeah I also like to play a 30 khz tone through a small tweeter, everyone says they can't hear it. But then when I turn it off and back on most can tell when it is on. A few question if they are hearing sub-harmonics. I let them use any of the analyzers we keep around to see if they can find it, so far no. (The 30 khz level is about 75 db, looking for 10 or 15 it is below the noise floor, but that doesn't mean it is not there and the ear can pick signal out of noise. (An example of where the ear is better than instruments... maybe))

Well break time over...
 
Really? It was beyond Dick Olsher's capability to look inside, see a dreaded opamp at the input, then draw his conclusions?

Actually reviewing is a really tedious process after the novelty wears off. Looking inside and seeing the I.C. case doesn't particularly tell where the part is in the circuit. They could be used for metering etc.

I suspect it is quite plausible that he can hear a difference between an I.C. opamp high gain feedback circuit and a low open loop gain discrete circuit. His preference would seem to be discrete.

Now if there was training involved, for example he used to look inside, that could have tuned his bias. So if the review sells your product... You should be more successful following the pied piper.

Unfortunately I cannot build a discrete opamp exactly the same as an I.C. There are some things available in both technologies that can be used to advantage.



As to large diaphragm vs small diaphragm condenser mic, when I do an arena, ballpark, or stadium, the required mic is almost always a miniature condenser headset. I also provide a large diaphragm condenser. Sometimes I get complaints the announcer cannot be heard. These usually turn out to mean he cannot be understood. Also turns out they can't be understood even from a recording. For some funny reason it is much less of a problem with the large diaphragm mic.s. Although some announcers who use them do turn their heads or "eat" them.
 
I did find a review of the original Parasound 2200 Mk1, that failed to make the grade. It was in the April 1992 issue of 'Stereophile' They did know about the IC in the input.
However, it was reviewed by Bob Harley, not Dick Olsher, who was not at the magazine at the time. The second review, or the Parasound 2200 Mk2, was apparently in the March issue in 1994, in the same magazine. I can't find it as of yet.
 
I would again like to state my design philosophy as to audio designs.
I have found from experience, and sometimes, failure, that a circuit should be as simple in thru-path as possible, as fast as possible, have the highest open loop bandwidth that is practical, and the lowest higher order odd distortion that I can get, as well.
However, EVEN meeting these criteria, I have made design failures, that general measurement will not show as to why.
These failures are not caught by ME, but by my clients, golden eared friends, and audio reviewers. I listen to them when I go astray, and that is the secret to my success in audio design.
Many other engineers, often better university educated than I am, could care less what the public, the audio experts, or what anyone else thinks about their audio designs, and point to their cost effectiveness, or good measurements of the traditional kind. This is what we commonly refer to as mid-fi. It is sold everywhere. When it goes out, it is usually best to throw it in the trash. Why bother fixing it?
That's not true of most of my designs, at least in my experience.
The point of my being here on the Blowtorch thread has been to give input on what I have found has worked, above and beyond traditional measurements. When I get a chance, I hope to continue.
 
If memory serves, he's the reviewer who slagged the amp, making a big point in the review about the opamp. Fashion has its inconveniences.

Sy,

Even with faulty memory I gotta give you this one. If a reviewer tells you the opamp is the problem he is listening with his eyes. The only exception is if he had as close a copy as can be without one. Then he can state his preference.

John,

If they want to buy a pink Cadillac sell it to them.

Scott,

I was serious about an opamp recommendation.

ES
 
The real story is that I told someone in a phone interview that I thought that bypassing the IC was the real change that made the difference. I didn't expect anyone to put it in the magazine, as I didn't want the situation that we have now. Now that it is here, I stick with my opinion, as I modified several MK-1's, including my own and got subjectively better performance.
 
Sy,

Even with faulty memory I gotta give you this one. If a reviewer tells you the opamp is the problem he is listening with his eyes. The only exception is if he had as close a copy as can be without one. Then he can state his preference.

John,

If they want to buy a pink Cadillac sell it to them.

Scott,

I was serious about an opamp recommendation.

ES

AD8065 is probably overkill but should work.
 
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