6N16 12x preamp srpp/cathode follower with printed circuit board design. - Page 5 - diyAudio
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Old 26th February 2012, 12:33 PM   #41
Koifarm is offline Koifarm  Netherlands
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Last week i have make me the headphone PCB. And today i assembled the board with the parts i already got. I still waiting for some parts. But here a preview of the board.

Click the image to open in full size.

Last edited by Koifarm; 26th February 2012 at 12:35 PM.
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Old 26th February 2012, 01:24 PM   #42
Koifarm is offline Koifarm  Netherlands
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For the headphone amp i have created a new thread.

6N16 headphone amplifier
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Old 14th April 2012, 11:42 AM   #43
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I have never understood why people insist on adding a cathode follower to the output of an SRPP in a preamp. The SRPP has a better load driving capability than the cathode follower so the latter is rather superfluous. Or have I missed something?

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Ian
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Old 14th April 2012, 12:27 PM   #44
Koifarm is offline Koifarm  Netherlands
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Quote:
Originally Posted by ruffrecords View Post
I have never understood why people insist on adding a cathode follower to the output of an SRPP in a preamp. The SRPP has a better load driving capability than the cathode follower so the latter is rather superfluous. Or have I missed something?

Cheers

Ian
Ian, the SRPP has the lowest distorsion when driving a high impedance.( read Elektor Audio special part 5) Then you can not drive a highcurrent source. Therefore you need behind the SRPP a bufferstage of any kind. It is all about choices and what you like for sound. For me i learned over the years that i like no feedback designs, SE amps, and circuits with as less sand as possible.
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Old 14th April 2012, 01:11 PM   #45
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Quote:
Originally Posted by Koifarm View Post
Ian, the SRPP has the lowest distorsion when driving a high impedance.( read Elektor Audio special part 5) Then you can not drive a highcurrent source. Therefore you need behind the SRPP a bufferstage of any kind. It is all about choices and what you like for sound. For me i learned over the years that i like no feedback designs, SE amps, and circuits with as less sand as possible.
Every tube circuit has it lowest distortion driving a high impedance. If you want low distortion then the SRPP topology is not your first choice; a regular CC stage would probably do better and your best bet would be a mu follower.

Cheers

Ian
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Old 14th April 2012, 01:21 PM   #46
SY is offline SY  United States
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Quote:
Originally Posted by Koifarm View Post
Ian, the SRPP has the lowest distorsion when driving a high impedance.( read Elektor Audio special part 5)
You might try to find Merlin Blencowe's excellent article on SRPP (AudioXpress, May 2010). He showed (and I did some measurements of my own and confirmed) that there's an optimum load for the SRPP where distortion reaches a minimum. That load is surprisingly low.

A common cathode stage has lowest distortion into a high load, but this is NOT the case for SRPP.
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Old 14th April 2012, 03:08 PM   #47
Koifarm is offline Koifarm  Netherlands
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SY, i just read the article. And it says all i know and confirm why i like the sound of the circuit.

Article: SRPP_Blencowe.pdf

Quote:

Whether or not the SRPP really is an SRPP depends on the load. If there is no load on the valve (e.g., it is DC coupled to another stage) then there is nowhere for current to go but straight through both valves, and so the stage is entirely single-ended, as in fig. 4a. This is not an SRPP but a common-cathode gain stage with an active load, and the maximum peak current flow is then equal to the quiescent current, as it always is with single ended operation. Such a circuit is obviously intended only for voltage gain, and is not widely used*.

So the first stage is a commoncathode stage with an active load. With operate single ended.
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Old 14th April 2012, 08:02 PM   #48
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Originally Posted by Koifarm View Post
SY, i just read the article. And it says all i know and confirm why i like the sound of the circuit.

Article: SRPP_Blencowe.pdf

Quote:

Whether or not the SRPP really is an SRPP depends on the load. If there is no load on the valve (e.g., it is DC coupled to another stage) then there is nowhere for current to go but straight through both valves, and so the stage is entirely single-ended, as in fig. 4a. This is not an SRPP but a common-cathode gain stage with an active load, and the maximum peak current flow is then equal to the quiescent current, as it always is with single ended operation. Such a circuit is obviously intended only for voltage gain, and is not widely used*.

So the first stage is a commoncathode stage with an active load. With operate single ended.

Unfortunately that article contains a number of errors, but nevertheless it is true that an SRPP stage distortion varies with load. With no load you may choose to call it a CC with an active load but the active load is a poor one and the plate load is only about the top tube's cathode resistor multiplied by its mu and that is why the SRPP has a typically high distortion even with no load. As I said before a better active load is the mu follower which will produce significantly less distortion. And as I said before a straightforward CC stage operating into a CF will produce less distortion than an SRPP. So I ask again, what is the point of the SRPP stage?

Cheers

Ian
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Old 14th April 2012, 08:48 PM   #49
Koifarm is offline Koifarm  Netherlands
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Ian,

when i compare the Cc - Cf with a SRPP of the same tube with the same components. I prefer the sound of the SRPP. But i can understand that another likes another kind of stage. Listening experience is for everybody different.

If higher distorsion would tell that the sound is bad, nobody would use tubes again. It is all about the tubes and components you use. And that is what i like about DIYaudio.
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Old 14th April 2012, 09:14 PM   #50
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Originally Posted by Koifarm View Post
Ian,

when i compare the Cc - Cf with a SRPP of the same tube with the same components. I prefer the sound of the SRPP. But i can understand that another likes another kind of stage. Listening experience is for everybody different.

If higher distorsion would tell that the sound is bad, nobody would use tubes again. It is all about the tubes and components you use. And that is what i like about DIYaudio.
That's fine. If you choose it because you prefer the sound then that's OK.

Cheers

Ian
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