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Cathode Bias confusion
Cathode Bias confusion
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Old 13th August 2017, 01:16 AM   #61
45 is offline 45  Italy
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Originally Posted by Wavebourn View Post
Gentlemen, the only way to cancel the function (2 stage) is to multiply it by an anti-function. Have you seen any anti-tube? I did not. You can substitute one from another in PP, but the result would be, only DC and even order parts would be decreased.
So what I see on the scope is a miracle?
It's just about even fuctions and the phase of the amplified signal (including its harmonics). It is only about 2nd harmonic and it's not complete cancellation (i.e. not reduced to zero).

PRR tried to explain that in simple words, I think.

Last edited by 45; 13th August 2017 at 01:30 AM.
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Old 13th August 2017, 02:04 AM   #62
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Gents, I think, the truth is in between, as always.
The carefully picked tubes and adjusted operating points can mutually exclude some THD to the pleasing wow! point of listening, seen that (I mean: heard).
So we are here down to the specific schematics i.e. combination of tubes, voltage, traffos etc etc.
Though, of course, some basics be obeyed. .. that's what we are cookin' of that old technology ))
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Old 13th August 2017, 05:26 PM   #63
gabdx is offline gabdx  Canada
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Using a row of devices with inverted signal can cancel 'something' on your scope like you can built perpetual motion devices, I am sure you can do both.
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Old 13th August 2017, 05:35 PM   #64
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Cathode Bias confusion
It's nothing like perpetual motion devices, inter-stage distortion cancellation techniques have been used since the 30's, perhaps even earlier...
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Old 13th August 2017, 05:39 PM   #65
45 is offline 45  Italy
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Originally Posted by gabdx View Post
Using a row of devices with inverted signal can cancel 'something' on your scope like you can built perpetual motion devices, I am sure you can do both.
Scope I meant a true analyzer, not even a crap sound card.
If you don't how to do it it doesn't mean that it is not possible. It is just not accessible to you or maybe you have done it by chance without being aware. Who knows...with the total confusion even about basic things you have in your mind eveything is possible!
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Old 13th August 2017, 08:06 PM   #66
Wavebourn is offline Wavebourn  United States
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Cathode Bias confusion
Quote:
Originally Posted by jazbo8 View Post
It's nothing like perpetual motion devices, inter-stage distortion cancellation techniques have been used since the 30's, perhaps even earlier...
Yes, for true believers.
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Old 13th August 2017, 08:32 PM   #67
45 is offline 45  Italy
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Originally Posted by Wavebourn View Post
Yes, for true believers.
Then can you explain how you can get 0.15% THD @1W and 3% @8W distortion from a 3x4P1LSE, without any other feedback? Scale the power down for your SE and see what you get. Do you get that THD at 0.33W and 2.66W. I don't think so.....And it is not the different OT.

Last edited by 45; 13th August 2017 at 08:39 PM.
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Old 13th August 2017, 11:23 PM   #68
45 is offline 45  Italy
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Same identical amp with a (stand alone, very) linear voltage amp instead of ECC82 running at 242V/1.3mA with 100K plate resistance. Only other difference is plate voltage at 283V instead of 263V (that only brings more power).
Distortion never gets down to 0.15%. Even at 0.1W!
So I should believe that increasing the plate voltage by just 20V I will get such striking difference and/or the ECC82 is most linear device in any condition?
Attached Images
File Type: jpg 4P1Lx3 PSE(10W) Stereo amp-4.jpg (185.8 KB, 55 views)

Last edited by 45; 13th August 2017 at 11:28 PM.
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Old 13th August 2017, 11:47 PM   #69
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4P1L is specifically known for being super-linear triode-strapped, I do not get it why somebody turn its worthmost into the worthless. .. or we are talking about personal preferences then.
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Old 13th August 2017, 11:51 PM   #70
45 is offline 45  Italy
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Originally Posted by Shef View Post
4P1L is specifically known for being super-linear triode-strapped, I do not get it why somebody turn its worthmost into the worthless. .. or we are talking about personal preferences then.
No better than others. Paralleling tubes makes linearity worse no matter how well they are matched. In fact 2x4P1L in parallel are not better than a 2A3. Here there are 3 in parallel.....

Last edited by 45; 13th August 2017 at 11:56 PM.
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