Well the noise level is very low so that is very quiet as claimed. EL34 can output 120V at 1.5% THD if bias @ half HT (+125V), then if only 1 to 10V is required to drive the hp. that is still very good bias point. Second, gain of 6SN7 stage can be reduced and also bias EL34 @ about 1/2 HT, so what gain do you want so I can try to come up one meet your need.
How about these changes?
THD 0.05% @1Vp out 300 ohms hp
Max gain ~3
Output impedance ~70 Ohms
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Hi
A suggestion : to use the double triode 6SN7 in SRPP mode rather than to put 2 triodes in parallel.
This tube is perfect for that as its µ is constant when Ip > 5 mA. It will give very low harmonic distorsion.
Polarization points should be revisited but maybe Koonw can give a try with Spice.
B+ for SRPP can be reduced introducing a RC network in the B+ line.
Jacques
A suggestion : to use the double triode 6SN7 in SRPP mode rather than to put 2 triodes in parallel.
This tube is perfect for that as its µ is constant when Ip > 5 mA. It will give very low harmonic distorsion.
Polarization points should be revisited but maybe Koonw can give a try with Spice.
B+ for SRPP can be reduced introducing a RC network in the B+ line.
Jacques
Well done, Koonw !
0.1% is very low and excellent in my point of view.
In sims, noise floor depends on the sim parameters.
Real noise floor will be higher, no matter the stage, because of the real PSU.
So I think it is a good circuit Merlin el mago can try. Not too much components to change.
Jacques
0.1% is very low and excellent in my point of view.
In sims, noise floor depends on the sim parameters.
Real noise floor will be higher, no matter the stage, because of the real PSU.
So I think it is a good circuit Merlin el mago can try. Not too much components to change.
Jacques
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