John Curl's Blowtorch preamplifier part II - Page 1238 - diyAudio
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Old 22nd May 2011, 06:50 PM   #12371
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Quote:
Originally Posted by john curl View Post
I think that global negative feedback is great IF the open loop bandwidth is higher than the useful bandwidth. However, that is seldom the case, except for the original JC-2 line amp, or the CTC Blowtorch. That is the 'secret' to my success!
Sorry John, you think wrong as Bruno's article clearly shows.
He unequivocally showed that there is no advantage, only disadvantages, for having an open loop bandwidth as wide as possible.
You can easily raise the gain when going to lower frequencies (which looks like lowering bandwidth) with only positive effects.
But, if you think he made a mistake somewhere (other than your tired 'for me it sounds better'), please educate us! Better yet, write a Letter to the Editor and I put it up for all of us to read!

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Old 22nd May 2011, 08:38 PM   #12372
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That is what I believe, of course, USEFUL bandwidth is essentially the frequency response of the human ear, in this case, just so that you know what I am trying to state.
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Old 22nd May 2011, 08:40 PM   #12373
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Unfortunately, Richard Sequerra and Mitch Cotter disagree with Bruno, and they have more experience and education. I will side with them.
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Old 22nd May 2011, 08:44 PM   #12374
DF96 is offline DF96  England
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I guess it is just possible that harmonic masking could be an explanation i.e. you can reduce the perception of distortion by adding more distortion at lower frequencies. Alternatively, the pleasure of low-order distortion outweighs the pain of high-order distortion. But this can't be right, because it would mean that the wider bandwidth amp isn't better, but worse in a nicer way!
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Old 22nd May 2011, 08:48 PM   #12375
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PIM will not go away, just because people want it to. Look at Ron Quan's paper for further details.
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Old 22nd May 2011, 09:45 PM   #12376
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Quote:
Originally Posted by john curl View Post
Unfortunately, Richard Sequerra and Mitch Cotter disagree with Bruno, and they have more experience and education. I will side with them.
John, I guess you could also add Matti Otala here.
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Old 22nd May 2011, 11:10 PM   #12377
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I detect a bit of 'RT' here (reverse trolling). ;-)
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Old 22nd May 2011, 11:58 PM   #12378
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Matti and Walt Jung as well! Just talked to Walt this week. '-)
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Old 23rd May 2011, 12:06 AM   #12379
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Quote:
Originally Posted by janneman View Post
Sorry John, you think wrong as Bruno's article clearly shows.
He unequivocally showed that there is no advantage, only disadvantages, for having an open loop bandwidth as wide as possible.
I think you can only make that statement if you have a narrow criterion
by which to judge advantage.

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Old 23rd May 2011, 06:13 AM   #12380
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Originally Posted by Nelson Pass View Post
I think you can only make that statement if you have a narrow criterion
by which to judge advantage.
I would agree with that.

Along those lines, late last year there was a full-page ad in TAS saying that you were coming out with a new zero-feedback amp. I haven't seen that materialize. Did I misread that ad, or is the amp still in the pipeline?

Just curious. You don't need to answer if it's not appropriate.
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