John Curl's Blowtorch preamplifier part II

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Buzzforb, you are asking a question that has an almost arbitrary answer. There are many ways to bias the fets. Usually we do the simplest approach.

My apologies John. I forget sometimes that other people don't live in my mind with me. Makes me a terrible communicator. Her are the two schematics I am comparing. A variation of the first is already layed out on Eagle, but I am interested to see what benefits are derived from the second.
 

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I would like to clarify my position on audio quality. I know that many people think that I am some sort of marketing person, but I am not. In fact, most of 'marketing' gets upset if I openly talk about one of my designs to anyone in the press.
Now, I am not saying that there is not such a thing as audio marketing. Of course there is! And it does really help to sell products. If it didn't, nobody would go to CES, hi fi shows, or advertise in magazines. But, I do not do audio marketing, never have, never will.
For example, I never ran an ad for a Vendetta Research phono preamp. It was all 'word of mouth' from reviews, dealers or maybe sometimes: importers.
Compare that to HK and Bose! YET, I got great reviews (mostly) and have been remembered even after 20 years of ceasing production.
You try that, sometime.
Why? Because I add VALUE to my designs with due diligence to anything and everything that I can find that might change the sound quality of the product, and the more I have control over both design and production, it just happens that those products become 'extra special' in the audio marketplace, just like early Marantz tube equipment. This is a 'fact' not a national hallucination.
 
I would like to clarify my position on audio quality.

There is no contradiction here, and I suppose you know it. Fact is, solid audio engineering only doesn't sell - you already acknowledged this fact.

So the options are: a) mass production and sell it for cheap to the unwashed masses (aka "mid-fi"), or b) build a "hi-fi" legend, which necessary has to contain at least one secret sauce, and price it accordingly obscene. The marketeers, reviewers, dealers, importers, thick wallet snobs, etc... will pick from there and do the rest (if they smell the money). In both cases, the amount of money that lands today in the audio engineer/designer pocket is insignificant, so the option for the a) or b) business models is, from the designer perspective, driven today by the Maslow high ranking needs only. Chose b) if you feel an urge to add "of (...) fame" to the paycheck. Does anybody know who designed the latest HK stereo?

Of course, it is naïve and a waste of time to expect a designer that made his choice for the b) business model over 30 years ago, to admit otherwise today.
 
About tube vs SS

John,

Perhaps you like the sound in 2nd harmonic distortion :)

Perhaps the tube amps & tube PSUs tend to have lower noise than SS amps & SS PSUs- both static & dynamic.

Perhaps the tube amps tend to have less have less 4th - 20th HD than SS

Perhaps you like the sound of transformers !

With these points in mind perhaps SS amps can be worked on to sound nicer.

Or perhaps just switch to designing tube amps ;)
 
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I set out a few years ago ( perhaps naively ) to try and design a solid state power amp that would encompass many of the musical qualities of well designed valve amp without losing the benefits of solid state.

Recently I was able to make a comparison with a friends DIY 300B SET.
At the time the valve amp was reproducing instruments with a little more natural timbre than my SS design - but there wasn't that much in it and thus encouraged I have done various mods to attempt to close that gap and I'm quite encouraged with the results thus far.
I don't believe there's any real mystery; to grossly over-simplify, SS is more prone to unpleasant low level distortion, not easily or typically measured; the "more natural timbre" of tubes is actually the absence, or lower audible levels, of those distortion elements being present in the reproduced sound. As you say, if sufficient effort is put into the exercise then no real gap exists between valve and silicon "sound".

I haven't heard any valve sound for many, many years that has done anything for me, in the sense of me pricking up my ears and saying, there is something really special happening here; all I can hear often is too much added syrup, :) ...
 
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I would love to read it. Any chance? :)

Unless someone else in here has a recollection of the year (I would guess maybe late 1970's or early 1980's) and a set of TAS, it will either be dependent on a good TAS back issue search engine or a visit to a big library and a lot of scanning of tables of contents. I believe it dates from the years the one cover artist did an original composition each issue, for which the reader was supposed to guess the accompanying phrase (for example, a loudspeaker driver on a podium was The Speaker of the House).

The likelihood of my digging it out is small, as all of the saved magazines are densely packed in boxes and not cataloged. At least I can locate my books for the most part.
 
Distortion is what makes tubes sound pleasing. That's really is all there is to it.
What one might call, "enhanced low-level details", another could just as easily call "compressed dynamic range".

Don't agree with this statement.

For me tube amps sound pleasant despite the high levels of 2nd HD not because of it.

My SS amps have become more & more "tube" like with much better low level detail as I have developed them principally through reducing static & dynamic noise.

I believe that low static & dynamic noise is a big factor of why tube amps have pleasant sound and a little bit of 2nd HD doesn't do any harm

SS amps may "sound" more dynamic but it's easy to add a false sence of dynamics to a SS amp merely by adding some PSU noise into the mix. For me this is not High Fidelity - but I have noticed that some people seem to like it.
 
I don't believe there's any real mystery; to grossly over-simplify, SS is more prone to unpleasant low level distortion, not easily or typically measured; the "more natural timbre" of tubes is actually the absence, or lower audible levels, of those distortion elements being present in the reproduced sound. As you say, if sufficient effort is put into the exercise then no real gap exists between valve and silicon "sound".

Agreed SS can be worked on to sound similar to good tube amps but eventually I guess we bump into the natural limitations of each approach. Tube amps mostly need transformers so can lack grip in the bass but SS amps need to be more complex because the devices the not naturally linear.

This is why I'm so interested to hear a SIT amp - I have heard they have all the advantages of tubes i.e. they are naturally quite linear and all the advantages of being SS - pity they're so expensive and hard to find.
 
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You guys are about to get stuck in a thorny philosophical trap.
1) Good sound does not necessarily equal accurate sound
2) How would accuracy be judged?
3) How is good judged?
4) claims like lower noise (that can't be measured) against measurements that don't support the claims lead to conflicts that are not resolvable using rational means.
4) Who can make judgements? Who is the Solomon who could even resolve these debates?

If accuracy is a goal and methods of determining accuracy can be agreed upon this all is rational. If "good" sound is the goal it all becomes judgments and is driven by experiences and those will take sensory inputs other than sonic (its really impossible for them not to).

And if its personal judgments everything from added distortions, frequency response variations etc. could be part of what constitutes good. Floyd Toole did research on ideal speaker response and found the common preferred response was not flat. The unfortunate corollary to that is for recording engineers to compensate for the speaker with microphones and recording techniques that enhance the parts that the speaker are suppressing.

On the other side of the argument is that the sound recording really never existed in nature as an experience and the process and the artists involved are making a new experience with the tools available (techniques and eq) and raw material of the recording. Much as a photographer manipulates exposure, light angles etc. to capture what he can of the experience he its trying to capture. They are creating an experience that is representative of the original event. In which case all the pieces between the original acoustic vibrations and you sitting in front of speakers/headphones add/subtract from the final experience. Much as looking at the Mona Lisa under a fluorescent light would not give the color or dynamic experience the canvas is capable of, let alone what a reproduction of the Mona Lisa would provide. Everything, different hardware,software, locations, state of mind, desire to experience differences will influence the experience.

If you go down the good sound road it gets pretty rocky since there are no signposts, clear roadmaps or really goals and lots of dead ends. On the other hand accuracy needs some consensus as to the required measurements and goals and may prove far less exciting.
 
You guys are about to get stuck in a thorny philosophical trap.
1) Good sound does not necessarily equal accurate sound
I disagree strongly. What I call good sound equates to giving me the subjective experience of hearing live music, there is a naturalness, an ease, to what I'm listening to, even at high volumes, which overrides any other consideration. I've spent 28 years listening at different times to what I call "good sound" vs. hifi, and the former beats the pants off the latter every time. The "good stuff" has been achieved using every no-no in the audiophile vocabulary: opamps, cheap components, plain cables, no fussing with acoustics and room treatments - no sugary additives at any time. If the "accurate" stuff is as unpleasant to listen to as it often is, then I'll leave it to other good folk to "enjoy" that experience ... :D
 
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