John Curl's Blowtorch preamplifier part II - Page 2958 - diyAudio
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Old 19th November 2012, 11:35 PM   #29571
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It does not matter what Z the amp assumes. What does mater, resulting frequency and phase response, and that Z does not have dips that cause excess distortions or damage of the amp. For tube amps it can't go too high to damage an output transformer, but such high Z can't happen practically.
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Old 20th November 2012, 12:04 AM   #29572
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Speaking of power followers ...

I've always liked Andrea's

http://www.audiodesignguide.com/my/Follower_99c.gif

2nd article down:
http://www.audiodesignguide.com/my/index.html

The virtual ground is cool!
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Last edited by AudioLapDance; 20th November 2012 at 12:07 AM.
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Old 20th November 2012, 12:11 AM   #29573
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Quote:
Originally Posted by AudioLapDance View Post
Speaking of power followers ...

I've always liked Andrea's

http://www.audiodesignguide.com/my/Follower_99c.gif

The virtual ground is cool!
Yes, it is cool. And cathode follower was even called "Common Anode" stage, but since there were no p-type tubes available, and people wanted to use a single battery for both common anode and common cathode stages, it got common to use "common anode", "common collector", "common drain" stage through "common power supply". What Andrea did, he creatively avoided cliche that was not needed in this particular case: nothing else had been powered from the same power supply. Unlike the majority of "copy-paste" professional designers.
Respect.
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Old 20th November 2012, 12:17 AM   #29574
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Originally Posted by john curl View Post
The CTC Blowtorch measures relatively poorly, because there is no global feedback loop. It has an open loop bandwidth over 100KHz, however, and that is important (at least to me). Hirata? What do YOU know about the Hirata test? Ever try it? I have. This amp has no mechanism to trigger Hirata distortion.
Just asking if you've conducted the Hirata test on Blowtorch. I take it your answer is, "No."

Any chance of conducting Ron Quan's test on Blowtorch? I hear Dick Sequerra and some other gurus think this is real important?

Last edited by kgrlee; 20th November 2012 at 12:38 AM.
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Old 20th November 2012, 12:29 AM   #29575
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It does not matter what Z the amp assumes. What does mater, resulting frequency and phase response, and that Z does not have dips that cause excess distortions ..
Alas, practically no speaker designers follow your rules

Even KEF who made a song & dance about this on their Reference Series at the end of the last millenium.

This often makes life difficult for amp makers.

There's also the small matter of how the speaker reacts with the environment ..when it acts as a microphone. This IS affected by amplifier output Z

The cynical or naive might claim Mr. Marsh's -ve resistance is just improving this bit especially at LF. Baxandall's paper gives you some clues but you need to swot up on theory of speakers to grasp its full significance.

Wave, do you compensate for the bass resonance impedance peak?

Last edited by kgrlee; 20th November 2012 at 12:32 AM.
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Old 20th November 2012, 01:00 AM   #29576
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Originally Posted by Esperado View Post
At the end, it is very complicated, and, as traditional loudspeakers can give enough listening pleasure, and because i'm old and lazy...
How were you able to read my mind ...?

Simple put, very conventional systems can create remarkably pleasurable sound, enough that all this worrying about the n'th, n'th of whatever is quite pointless -- at least for me ...

Frank
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Old 20th November 2012, 01:26 AM   #29577
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Quote:
Originally Posted by kgrlee View Post
Alas, practically no speaker designers follow your rules

Even KEF who made a song & dance about this on their Reference Series at the end of the last millenium.
"And they are the very people who would prevent us to pick our noses"?
Shame on them.

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Wave, do you compensate for the bass resonance impedance peak?
No, I don't. I am too lazy. Audyssey compensates for me, for everything.

I only have a microphone transformer shunted by 0.1 Ohm resistor in series with subwoofer, for PFB by current. Why transformer? because the amp is bridged, class D.
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Last edited by Wavebourn; 20th November 2012 at 01:51 AM.
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Old 20th November 2012, 01:59 AM   #29578
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Originally Posted by fas42 View Post
Simple put, very conventional systems can create remarkably pleasurable sound, enough that all this worrying about the n'th, n'th of whatever is quite pointless
To be complete, when we decided to abandon the research of servoed loudspeakers for industrial production, because we had here or here some nice results in the middle of problems, i had the feeling that we loosed something because i was not able to adress-it correctly.
It is teasing, i understand Mr. marsh appetite. I would love to have a reaction from mr. Kglee's experience vs mine, if I'm not in his ignore list.

BTW: Why don't we use Constantan wires for the loudspeakers moving coils ?
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Old 20th November 2012, 02:01 AM   #29579
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Default Amplifier question

Hello kgrlee

What power amplifer do you use when listening .
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Old 20th November 2012, 02:06 AM   #29580
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Quote:
Originally Posted by Esperado View Post
BTW: Why don't we use Constantan wires for the loudspeakers moving coils ?
Because that would make the voice coil run much hotter than using copper. Also probably poorer eddy current damping but that might not be an issue in some cases.
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