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Old 15th June 2018, 11:08 AM   #31
6A3sUMMER is offline 6A3sUMMER  United States
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I came upon this thread late in the posts. I only read from post 21 & on.

Post 21 had one question: is this classic and standard circuit for push pull ?

I should have simply said no it is not.
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Old 15th June 2018, 11:28 AM   #32
jazbo8 is offline jazbo8
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First DIY tube amp
At least you spot it as SE, I missed it completely because I assumed we were still talking about PP amps, well you know what they say about assume...
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Old 15th June 2018, 06:51 PM   #33
guitarnerd is offline guitarnerd  Taiwan
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Well, I was more interested in these part of the circuit (in the attachment)
Looks like some kind of compensator? thought I might saw similar ones somewhere
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Old 16th June 2018, 02:45 AM   #34
PRR is offline PRR  United States
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Quote:
Originally Posted by jazbo8 View Post
The Williamson amplifier is arguably the first "modern" tube amp design, .... Definitely pentode, as Williamson detested the "ultralinear" connection. ...!
Um, IIRC, the Williamson was "triode" power stage. By necessity, it used triode-strapped KT66 (beam tetrode, patent-evading pentodes) (good big triodes were fading from the scene), but was triode operation.
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Old 16th June 2018, 08:54 AM   #35
jazbo8 is offline jazbo8
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Quote:
Originally Posted by guitarnerd View Post
Well, I was more interested in these part of the circuit (in the attachment)
Looks like some kind of compensator? thought I might saw similar ones somewhere
Yes, they are for NFB compensation, but those are not on your schematic.
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Old 16th June 2018, 10:33 PM   #36
6A3sUMMER is offline 6A3sUMMER  United States
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guitarnerd,

Where did you get those schematics in post # 33? I do not remember seeing those. They almost look like some passive frequency response networks for something like phono preamps, or similar.

Take a look at the dyna stereo 70:

dyna st 70 schematic - Google Search

It has 2 negative feedback compensation networks:

1. A series RC (82pF 18kOhm) dominant pole from the input Pentode plate to ground (often found in amps). The dominant pole on your amplifiers may be your output transformer.

2. A capacitor from the screen of the bottom output pentode (Ultra Linear tap) back to the input Pentode cathode circuit (very unusual). Instead, these compensation caps are more often connected from the output transformer secondary (across the main negative feedback resistor) to the input pentode cathode circuit.

The main feedback resistor is 1k Ohm from the output transformer 16 Ohm tap to the input pentode cathode circuit.

With negative feedback that comes from the output transformer secondary to the input cathode, there are usually a self bias resistor and bypass cap in parallel from the cathode, with the bottom of that network to another resistor to ground. The negative feedback is applied to the junction of the bottom resistor and the self bias network.

Last edited by 6A3sUMMER; 16th June 2018 at 10:44 PM.
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Old 17th June 2018, 02:25 AM   #37
hooman is offline hooman  Iran
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Quote:
Originally Posted by 6A3sUMMER View Post
guitarnerd,

Where did you get those schematics in post # 33?
I do not remember seeing those.
.
post...22
post....23

Quote:
Originally Posted by guitarnerd View Post
Well, I was more interested in these part of the circuit (in the attachment)
Looks like some kind of compensator? thought I might saw similar ones somewhere
if have more gain can use this kind of passive circuit for high frequency response .
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