Metropoulos 2203 replica, with a few tweaks

[hotguit]

hi george
Do you suggest to try 56k/250pico or 56K/470 pico tone stack?
so no cap on 10K; 4,7K on cathode increase gain significantly (imho of course); maybe a 8,2K or 6,8K.
Can't you tell more about the tone stack?
thank you
hot

[syscokid]

Capture1.JPG (90.33 KiB) Viewed 3157 times

I'm trying to have fun in figuring out what you got there...

The tone stack resistor looks like it's still a 33k. Could a smaller cap, like a 330 or 250pf increase mids?

The cathode resistor looks like a 4.2K ...too hard to tell...

[hotguit]

don't know what thinking.
george told that only cathode and tone stack tweaks were made.
Hope he wants to tell more about that tweaked 2203.
hot

[VelvetGeorge]

Sorry I didn't document that one better. It is almost certainly a 250p or 330p in the tone stack. 4.7k cathode. I put a small cap across the plate resistors to stabilize things, not larger than a 10p or 22p.

george

[syscokid]

Sorry I didn't document that one better. It is almost certainly a 250p or 330p in the tone stack. 4.7k cathode. I put a small cap across the plate resistors to stabilize things, not larger than a 10p or 22p.

george

Thanks for dropping some beans, George. I must have stared and enhanced that picture for about an hour, and didn't even notice the cap between the plate resistors...

[SteadyEddie]

Increasing the treble cap to, say, 1000pf or higher will give a mid boost and apparent increase in gain. I've done it to my plexi and it sounds great with a Strat. Good increase in sustain.

[hotguit]

Increasing the treble cap to, say, 1000pf or higher will give a mid boost and apparent increase in gain. I've done it to my plexi and it sounds great with a Strat. Good increase in sustain.

what do you mean with "trebble cap"? the 470 p across voltage divider (470K)? or the 470pico across the 470K between V1A and V1B?

summarizing the tweaks on george's amp:
V1 cathode res. = 4K7
cap between plates (not across but between plates res.) = 10 p - 22 p. (i think 22 p.)
slope res 47K or 56K
tone stack cap = 250 p - 330 p.
ANY HELP WELCOME

Need a volunteer with a ptb board to try this tweaks. (too much difficult on a pcb )
hot
p.s.
thank you George, your help is always appreciated

[VelvetGeorge]

Tone stack resistor should be 33k. And the cap is either 250 or 330.

I may have tried 2.7k cathode value, but settled at 4.7k.

George

[SteadyEddie]

The tone stack treble cap. Raise it to 1000pf and you get thicker upper mids and more sustain

Increasing the treble cap to, say, 1000pf or higher will give a mid boost and apparent increase in gain. I've done it to my plexi and it sounds great with a Strat. Good increase in sustain.

what do you mean with "trebble cap"? the 470 p across voltage divider (470K)? or the 470pico across the 470K between V1A and V1B?

summarizing the tweaks on george's amp:
V1 cathode res. = 4K7
cap between plates (not across but between plates res.) = 10 p - 22 p. (i think 22 p.)
slope res 47K or 56K
tone stack cap = 250 p - 330 p.
ANY HELP WELCOME

Need a volunteer with a ptb board to try this tweaks. (too much difficult on a pcb )
hot
p.s.
thank you George, your help is always appreciated

[hotguit]

The tone stack treble cap. Raise it to 1000pf and you get thicker upper mids and more sustain

Increasing the treble cap to, say, 1000pf or higher will give a mid boost and apparent increase in gain. I've done it to my plexi and it sounds great with a Strat. Good increase in sustain.

what do you mean with "trebble cap"? the 470 p across voltage divider (470K)? or the 470pico across the 470K between V1A and V1B?

summarizing the tweaks on george's amp:
V1 cathode res. = 4K7
cap between plates (not across but between plates res.) = 10 p - 22 p. (i think 22 p.)
slope res 47K or 56K
tone stack cap = 250 p - 330 p.
ANY HELP WELCOME

Need a volunteer with a ptb board to try this tweaks. (too much difficult on a pcb )
hot
p.s.
thank you George, your help is always appreciated

thank you
i'll try it
hot
p.s.
is the tone still "focused"?

[hotguit]

well
after george's last beans (thank you) the tweaks made shoul be:
V1 cathode res. = 4K7
cap between plates (not across but between plates res.) = 10 p - 22 p. (i think 22 p.)
slope res 33 K
tone stack cap = 250 p - 330 p.
Steady Eddie suggests a 1000 pico on tone stack (trebble)
Any help welcome
hot

[guns4hire34]

What does the 10p or 22p across the plate resisters do exactly?

[VelvetGeorge]

It's there to keep things stable, prevent oscillations.

George

[guns4hire34]

George,
Any certain voltage on those??

[syscokid]

George,
Any certain voltage on those??

Obviously I'm not George, but to be on the safe side, I would use 1kv. There's still quite-a-bit of voltage at the plates of V1.