bias supply problems and thoughts

[sluckey]

Take your bias output from the junction of R7 and R8. Connect R9 as a two terminal variable resistor. Now the circuit will be exactly like many Marshall amps. Then you will be able to increase the value of R1.

[Disabled_shredder]

so r8 will go to ground insead of the pot? i guess the question is if i do it that way i should be able to raise 4.7k back to 220k

[sluckey]

so r8 will go to ground insead of the pot? i guess the question is if i do it that way i should be able to raise 4.7k back to 220k

No. The only thing in your drawing that would change is the wire on the bottom side of the pot that is your bias output. Just move that wire to the junction of R7 and R8. The bottom side of the pot will have nothing connected to it.

I doubt you will be able to increase R1 to 220K, but it will certainly be greater than 4.7K. Just chose a value that gives you a healthy bias voltage range.

BTW, the circuit you drew will allow you to adjust the bias voltage to zero. That's potentially fatal for fixed bias output tubes. The circuit I proposed will not let you adjust to zero.

[Disabled_shredder]

many thanks sluckey. i will try that method as soon as i get the power amp section to fire ive been on that part way to long. i think this amp build is gonna kill me. i should have known not to design a custom from scratch amp. its a headache!

[Disabled_shredder]

so in a quick test to see what i could do and upon the good observation that i can pull the neg bias to 0 i changed r1 to a 2w 10k and added a 4.7k resistor to ground from the pot. not the marshall style but it gives me a minimum of neg 7.7 and a pos of 37-38 or so i cant remember now. ill mess with it more when i finish the power amp! thanks everyone for the help!