Plate loaded 6N6P over SRPP 6N6P any day of the week... - diyAudio
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Old 23rd February 2011, 11:12 PM   #1
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Default Plate loaded 6N6P over SRPP 6N6P any day of the week...

In my case. I decided to add an active stage after the RAKK DAC passive I/V section I have. I first lowered the resistor after the LL1674 transformers to 47 Ohm. And then added a 6N6P SRPP stage.

I got what I wanted in terms of speed. But something was amiss. No musicality. Ripped out one 6N6P and converted the SRPP to plate loaded 6N6P. The sound really came to life.

I'll pick the plate loaded version of the SRPP any day of the week. YMMV, IMO and all that.

PS. Bypass cap is 100uF/10V

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Last edited by Bas Horneman; 23rd February 2011 at 11:20 PM.
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Old 23rd February 2011, 11:39 PM   #2
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Do the transformer and 47R make up enough grid leak resistance? Seems low to me.
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Old 24th February 2011, 12:08 AM   #3
kevinkr is offline kevinkr  United States
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Quote:
Originally Posted by Miniwatt View Post
Do the transformer and 47R make up enough grid leak resistance? Seems low to me.
It's cathode biased so the resistance in the grid circuit can be anything from zero to the maximum acceptable grid resistance for the type of tube used.

I like choke loading as well and use it in some of my driver stages. The next phono stage may have them as well - the current one uses tube based gyrators.
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Old 24th February 2011, 07:24 AM   #4
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Hi Bass,
I'm working on a similar project. So I need to ask why 47R.
Resistors after the I/V transformer is used to be in the KΩ range.
A good idea would be to replace the anode choke with an output transformer.This would allow to throw away the coupling cap
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Old 24th February 2011, 08:24 AM   #5
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Originally Posted by Alkis View Post
A good idea would be to replace the anode choke with an output transformer.This would allow to throw away the coupling cap
I did that after my RAKK dac passive I/V. I had a single 6J5 drive the SILK 941 but it lacked speed in the low end. The circuit attached is what I am working on now, a few solder point and it will be up and running. I found that driving SILK 941 with low Z really improved speed/ attack in the low end but some of the resolution/ microdetail got lost adding more stages and a coupling cap. I think 6V7g/ecc88 won´t be the last attemt I do, and 6n6p driving my 941 by anode is up for a go next time.
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Old 24th February 2011, 08:34 AM   #6
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Hi andRookie

Isn't 210V too much for the ECC88 as the datasheet says max 130V plate-cathode.
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Old 24th February 2011, 09:28 AM   #7
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Hi andRookie

Isn't 210V too much for the ECC88 as the datasheet says max 130V plate-cathode.
Haven´t thought of that. During the test I used a 6N1P and it did not protest. I see I should just keep using it and not burn my ecc88s. Thanks!
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Old 24th February 2011, 03:50 PM   #8
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Originally Posted by kevinkr View Post
It's cathode biased so the resistance in the grid circuit can be anything from zero to the maximum acceptable grid resistance for the type of tube used.
I learn something new here every day

So I guess it's a matter of matching the resistor to the transformer impedance?
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Old 24th February 2011, 10:15 PM   #9
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Quote:
I'm working on a similar project. So I need to ask why 47R.
Resistors after the I/V transformer is used to be in the KΩ range.
Well yes, you'd use something in the kΩ range if it is passive. But I wanted the output stage to have a reasonable output similar to that of the passive stage. Maybe it is even lower I'm not sure. This way I guess the final gain is slightly lower than that of a typical cd player output.

I made a drawing error with the 260k resistor. And the I/V transformer is a 1674 ofcourse and not a 1694.
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Old 24th February 2011, 10:21 PM   #10
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A good idea would be to replace the anode choke with an output transformer.This would allow to throw away the coupling cap
I suppose so. I have so many projects still and funds are low. Plus I am very happy with the sound this way it's hard to believe it could be improved .

Last edited by Bas Horneman; 24th February 2011 at 10:23 PM.
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