I'm focusing on the phrases, "fast", "linear" and "very high dynamic headroom": they're the very qualities I hear missing from the majority of complete systems, here I use the terms "plodding", "distorted", and "groaning under stress" ... 🙂
Transformerless? I doubt it. I don't think you could parallel enough LSK389's and in any case why matched pairs.
If noise matching is similar to that of vacuum tubes, transformers with a 1:50 step-up would also apply. Fortunately not much inductance needed.
Thanks,
Chris
Thanks,
Chris
No I don't believe it was, nor did I or should I wish to imply that --- although a transformerless noise-matched design is feasible with sufficient numbers of paralleled parts. Indeed, there is no need for matched pairs.
As I remarked in a thread I started that has been pretty much ignored, the same FET 1/4 power reciprocal dependence of noise on drain current works for us in the other direction when doing massive paralleling, even for a limited overall available current, provided the capacitance does not get so high as to constitute a significant tau with the extremely low ribbon resistance. Another caveat is the possible departure from the noise/power law at very low currents per part.
But that's getting still further off topic and should be discussed perhaps in another ignored thread 😀 I just mentioned the linked article because (1) it was contemporaneous and (2) because it had a lot of information about Linear Integrated Systems and their parts (much of the founder's history was news to me). This, in turn, apropos of why one cannot build a form/fit/function identical CTC Blowtorch.
Very interesting tack. Could I pose a question?
Phantom48 can provide 170mW if matched. An ideal DC-to-DC convertor gives, say, 5 Volts at 34mA. If single-ended (not differential) does the noise equivalent resistance decrease continually with added paralleled devices? Or is there an optimum number with, say, 34mA available?
Thanks,
Chris
Phantom48 can provide 170mW if matched. An ideal DC-to-DC convertor gives, say, 5 Volts at 34mA. If single-ended (not differential) does the noise equivalent resistance decrease continually with added paralleled devices? Or is there an optimum number with, say, 34mA available?
Thanks,
Chris
You're on it. The best way to go is with high efficiency conversion of that available phantom power. But --- the paralleling advantage is unlimited, subject only to the caveat about departure from the 1/4 power model, which may indeed set in at very low currents.
I worked on such a design for a while, mostly as a stunt, until distracted by more immediately remunerative pursuits. A lot of the work was on the efficient but low noise power conversion.
Yes Wes is good people. We had the distinction of being shushed by Streicher at AES when we were giggling at each others' jokes, during the speaker's talk.
The goal should not be to recreate or copy a CTC Blowtorch. Like I stated several times the vision should be a preamp which confirms the requirements of nowadays audio systems. We now have digital components (CDP, Music server etc.) which deliver higher signal outputs. So we need a phono section with higher gain, and of course highest quality) and a line section with lower gain.
Gentlemen that's the vision and way to go.
Mr Wood,
you seem to have mentioned between a thousand and +5K of Mr Wurcer's favorite JFET in parallel.
🙂clown🙂
Ron Quan interview
Only slightly OT: John's buddy Ron Quan is interviewed here. (You need to scroll down to "The Tenacious Transistor Teacher"). Interesting person.
I have his book, and it is interesting in that it has lots of insights that are of use in audio design, even if the book's title suggests otherwise.
jan
Only slightly OT: John's buddy Ron Quan is interviewed here. (You need to scroll down to "The Tenacious Transistor Teacher"). Interesting person.
I have his book, and it is interesting in that it has lots of insights that are of use in audio design, even if the book's title suggests otherwise.
jan
JC wrote:
...a gain stage that is very fast, very linear and with very high dynamic headroom, is necessary, in order to minimize the duration of the 'ticks' and mistracking artifacts ...
To which you answered.
If you would extend that throughout the entire system with vinyl, your speakers would collapse.
When I listen to those stories about how much head room you need in a phono pre-amp in order to accomodate clicks and mistracking artifacts, the only thing I think is: at which stage are you going to shed those high peaks before they hit your speakers.
My guess is the best place to do that is with a low pass in the first stage of the phono preamp. That minimizes head room requirements in the rest of the chain.
...a gain stage that is very fast, very linear and with very high dynamic headroom, is necessary, in order to minimize the duration of the 'ticks' and mistracking artifacts ...
To which you answered.
If you would extend that throughout the entire system with vinyl, your speakers would collapse.
When I listen to those stories about how much head room you need in a phono pre-amp in order to accomodate clicks and mistracking artifacts, the only thing I think is: at which stage are you going to shed those high peaks before they hit your speakers.
My guess is the best place to do that is with a low pass in the first stage of the phono preamp. That minimizes head room requirements in the rest of the chain.
More likely, that the amp would collapse ... I'm a great believer in the idea that the typical power amp is the weak link, rather than the poor, derided speakers ... 🙂
True headroom is key to getting realistic sound, people who have artfully combined high quality, very sensitive speakers and powerful, reasonably competent amps know that one can generate intensely dynamic, realistic sound, with tonality intact.
This is not frequency related, this is maintaining accurate output level. You want to extend the headroom capabilities, not reign them in ...
I am affraid you missed my point. Some advocate phono preamps that have enough headroom to generate >20 V p/p signals. If you calculate how much this will be at 30 dB or so gain, it becomes obvious that even if you have an amplifier that can deal with it, which is what you advice, your speakers won't.
Therefore, you need to get rid of these peaks. Since the peaks are of very short duration, I believe a low pass filter will sort them out. I built in a roughly 50KHz low pass in the first stage of my phono amp that does just this (I hope). At any rate, it works well enough for me not to be bothered too much with pops and clicks.
Therefore, you need to get rid of these peaks. Since the peaks are of very short duration, I believe a low pass filter will sort them out. I built in a roughly 50KHz low pass in the first stage of my phono amp that does just this (I hope). At any rate, it works well enough for me not to be bothered too much with pops and clicks.
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