6SN7 SRPP - oscillating dc offset

[Cassiel]

I have already tried the heaters with a DC voltage reference and this configuration gives me less noise. Just a little less though. I'm thinking my next step will be installing high frequency filters. An input filter and a toroidal and resistor combo from signal ground to chassis ground. I have already tried the low picofarads caps to ground - nothing.

 

[lordearl]

Did you try re-wiring the socket for a different tube? 6cg7 will be quieter and needs no mods to the circuit. Output impedance is too high with either 6sn7 or 6cg7, so I use the ecc88 (pcc88).

6sn7 is so old. Like using a typewriter instead of a computer!

 

[lordearl]

Cassiel - I just checked my amp for tweeter noise. It is silent on the right channel and a little noisy on the left. I get the feeling it might be some AC interference. Is the noise in your amp present on both channels?

 

[Cassiel]

Yes, both channels. You may have a noisy tube.

 

[AudioMax]

Helo! I'm new on this forum
been searching around web to find mods for analog metric 6SN7 SRPP and i found it
Anyway.....i bought this kit long ago in high school and it found its place in old diy project room because it sounded like ****. So i see there is possible way to mod this thing.
So I'm planing to use this amp like a headphone amplifier (PC output > headphones) So do anyone know what to do to mod this board to sound good?
I'm planing to replace tubes for some tungsol 6sn7.
what else to replace to get some good sound from this?

 

[lordearl]

You'll never get enough drive from SRPP to power headphones......

 

[gregoryharding]

I've been considering building this same preamp. Is this a good design? Or would anyone recommend another using 6SN7's and SRPP circuit.