• WARNING: Tube/Valve amplifiers use potentially LETHAL HIGH VOLTAGES.
    Building, troubleshooting and testing of these amplifiers should only be
    performed by someone who is thoroughly familiar with
    the safety precautions around high voltages.

DC filaments for 6550s

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yes i could do with the 5K1 but i know the sound will be dull (less treble)...pretty much same as 4K7. in fact anything less than 100k seems to have bad treble. i use those values to cut the hiss im hearing and very little gain reduction. the primary wiring is in phase so no howling noticed whichever value used. i need to strike a balance between hiss reduction and treble loss here.

i was wondering if i used 5K1 on the NFB and played with the 6550 grid resistor values, would i get back the treble i lost in the nfb? the grid is now at 10k. or maybe the damping cct between the AX and AU needs a tweek. what do ya think?
 
As SY mentions,the o/p stage grid stopper values should have no effect on treble and playing with grid stoppers in an attempt to alter the treble is quite wrong.. Seems you have a serious component misplacement, have you double checked against the circuit diagram ?
I have a slightly modified GEC 88-50, the 5K1 is the correct value for 8 Ohm LS (20dB globbal nfb)with absolutely no loss of treble. In fact global nfb actually extends the top end range. Your input stage + phasesplitter should be pretty close to the enclosed jpg. I used a 6SN7 (better sounding) instead of ECC82 types.
richy
 

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