John Curl's Blowtorch preamplifier part II - Page 485 - diyAudio
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Old 1st July 2010, 07:20 PM   #4841
PMA is offline PMA  Europe
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Quote:
Originally Posted by SY View Post
Me. It seemed to sound just fine, as would any well-designed preamp being used in a suitable system.
There are pretty big differences in sound of even well-designed preamps, provided one is not deaf.
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Old 1st July 2010, 07:29 PM   #4842
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SY's listening experience with the Blowtorch was short and limited to what I had on hand. His response was polite and vague. His new phono design is no less elaborate than anything inside the Blowtorch, and I believe, a very good design.
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Old 1st July 2010, 07:35 PM   #4843
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Quote:
Originally Posted by john curl View Post
SY's listening experience with the Blowtorch was short and limited to what I had on hand.
What you had on hand was some pretty decent gear! So if there were anything actually deficient in the Blowtorch, it would have been pretty evident. There wasn't and it wasn't.
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Old 1st July 2010, 07:38 PM   #4844
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Quote:
Originally Posted by PMA View Post
There are pretty big differences in sound of even well-designed preamps, provided one is not deaf.
That's the claim. Evidence, OTOH, is singularly lacking.

Quote:
His response was polite and vague.
When I don't like something, I can be pretty impolite.
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Old 1st July 2010, 07:59 PM   #4845
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Hi Tino,

I just wanted to make note of the fact that the STASIS amps do not have a global feedback loop ,if you look at Nakamichi PA-7 schematic you see what I mean.

Jam
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Old 1st July 2010, 09:07 PM   #4846
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John,

"What is often overemphasized is damping factor. It is overrated. Somewhat higher output impedance and with a flatter characteristic tends to show that the amp uses less feedback and has a higher open loop bandwidth. Both are important. Higher open loop bandwidth is the key."

Could not agree more.


Patrick
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Old 1st July 2010, 10:08 PM   #4847
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Originally Posted by john curl View Post
What is often overemphasized is damping factor. It is overrated. Somewhat higher output impedance and with a flatter characteristic tends to show that the amp uses less feedback and has a higher open loop bandwidth. Both are important. Higher open loop bandwidth is the key.
But your JC-1 has a stellar damping factor, John.

Subjectively, sometimes a little physical or effective resistance in series with an amp output can add a pleasant coloration to the sound, but this has nothing to do with high open-loop bandwagon and low feedback.

Those loudspeakers that were voiced by the designer using an amplifier with low DF may sound better with a low DF amp, and maybe tight and harsh with a high-DF amp.

Cheers,
Bob
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Old 1st July 2010, 11:11 PM   #4848
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Pretty good, huh? Well, my high damping factor is on parallel with relatively high open loop bandwidth that I am more satisfied with, that high damping factor, itself. High numbers like this are marketing points, but the REASON for the high damping factor is the key. It is NOT just because of negative feedback.
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Old 2nd July 2010, 02:15 AM   #4849
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If you do not use a negative output impedance the effective damping factor is limited by the resistive element in the voicecoil shortcircuited in the case of a conventional dynamic speaker after Kellogg-Rice. Try it yourself, take a naked speaker, short the leads and try to move the cone. It is a bit harder to move the cone but not even a damping factor of 10.000 can change that situation. Negative output impedance and current drive work totally different but the voltage - in , voltage times gain - out topology is the overiding principle ussed today and for good reason. It simply works with most loudspeakers you connect to it and there is a huge variety on the market.
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Old 2nd July 2010, 05:02 AM   #4850
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I would generally agree, Joachim. However, LOW open loop output impedance can reduce IIM in feedback circuits. That is why my output stage has such a low output impedance. The output impedance is low, BEFORE negative feedback is applied.
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