Metropoulos Forum

5F1 CIRCUIT - im wondeirng if anyone can anyone point out how to make this amp break up earlier and what maybe causing it to clip past 8 ( unwanted clipping - sounds buzzy - unmusical - any ideas how to make it handle it at full volume - sound slike my guitar signal is making noise right out of the rectifier tube!

Unfortunately, low power single ended circuits like that just turn to fuzzy mush when dimed.
How much earlier could you want it to break up? I'd think the volume was tame enough to run it at six or seven and get plenty of grind. Not enough at that point?

Flames1950 wrote:Unfortunately, low power single ended circuits like that just turn to fuzzy mush when dimed.
How much earlier could you want it to break up? I'd think the volume was tame enough to run it at six or seven and get plenty of grind. Not enough at that point?

not enough at that point i would like to take this simple circuit and understand it some more - like understanding some say they remove negitive feedback on these? or up the bypass caps on the cathodes ( i think i actually get that from 25mfd to say 100uf,... i think...or lower V1 and V2 cathode resistors, down to 1K or even 820 omhs. And if not enough up the NFB resistor from 22 to 33K or so! it just sounds like my guitar signal is coming right out of the rectifier tube after 9, the thing is clipping...

rockstah wrote:

Flames1950 wrote:Unfortunately, low power single ended circuits like that just turn to fuzzy mush when dimed.
How much earlier could you want it to break up? I'd think the volume was tame enough to run it at six or seven and get plenty of grind. Not enough at that point?

not enough at that point i would like to take this simple circuit and understand it some more - like understanding some say they remove negitive feedback on these? or up the bypass caps on the cathodes ( i think i actually get that from 25mfd to say 100uf,... i think...or lower V1 and V2 cathode resistors, down to 1K or even 820 omhs. And if not enough up the NFB resistor from 22 to 33K or so! it just sounds like my guitar signal is coming right out of the rectifier tube after 9, the thing is clipping...

I dont know where you got that advice but when I was dfoing tweed fenders the thing was to lower the bypass cap values to like 5uy or 1u to try and clean up the mush and add NFB to give you more headrrom which will actually make it a bit tighter and elss mushy. Doing the opposite will only add gain and make the drive really messy. People dont often dime fender tweeds to 10. They really fall apart at that point. They do sound great with my TMB. I dont think your going to get a really rockin amp from a 5F1. Not marshallesque at least. Maybe rock in a stones kinda way or bluesy way.

Billy Batz wrote:

rockstah wrote:

Flames1950 wrote:Unfortunately, low power single ended circuits like that just turn to fuzzy mush when dimed.
How much earlier could you want it to break up? I'd think the volume was tame enough to run it at six or seven and get plenty of grind. Not enough at that point?

not enough at that point i would like to take this simple circuit and understand it some more - like understanding some say they remove negitive feedback on these? or up the bypass caps on the cathodes ( i think i actually get that from 25mfd to say 100uf,... i think...or lower V1 and V2 cathode resistors, down to 1K or even 820 omhs. And if not enough up the NFB resistor from 22 to 33K or so! it just sounds like my guitar signal is coming right out of the rectifier tube after 9, the thing is clipping...

I dont know where you got that advice but when I was dfoing tweed fenders the thing was to lower the bypass cap values to like 5uy or 1u to try and clean up the mush and add NFB to give you more headrrom which will actually make it a bit tighter and elss mushy. Doing the opposite will only add gain and make the drive really messy. People dont often dime fender tweeds to 10. They really fall apart at that point. They do sound great with my TMB. I dont think your going to get a really rockin amp from a 5F1. Not marshallesque at least. Maybe rock in a stones kinda way or bluesy way.

Billy i wondered about the advice as well
so what i think i might do is just remove v1's( and even v2's as well) bypass cap and see how it sounds, perhaps lower it to 5 or 1( 5uf and 1uf right?) after that. dont get me wrong here im not trying to marshallesque the amp, i am merly trying to clean up and try to get it to not clip so harshly ( the gain is great withouit the clipping, nonmusical buzziness going on)- it really sounds like the signal is coming right out of the rectifier tube past 9( it goes to 12) i figured i could learn more with this simple circuit.
What do you mean your TMB?
this amp has a great clean sound - what do you think?

The TMB is my Time Machine Boost pedal.

Yeah I eould use a 1u for the bypass cap on stage 1 or remove it. Id also try lowering the NFB resistor to 4.7k.

Billy Batz wrote:The TMB is my Time Machine Boost pedal.

Yeah I eould use a 1u for the bypass cap on stage 1 or remove it. Id also try lowering the NFB resistor to 4.7k.

i know i could figure this out but where is the neg feedback resistor?
the 22k on r10 ( between the 16 and 10 mdf caps?
love to get a great bluesy tone out of it - its nice sounding amp

Yeah I think its 22k in those amps. It leads form the output jack right?

[quote="Billy Batz"]Yeah I think its 22k in those amps. It leads form the output jack right?[/quote
to the output jack from the board is 56k like the picture above ^
i was thinking the resitor bewteen the 16 and 10 caps on th eboard

It looks like that 56k is the NFB resistor. Its way too high for that amp IMO. Id go to 10k at least right away.

Billy Batz wrote:It looks like that 56k is the NFB resistor. Its way too high for that amp IMO. Id go to 10k at least right away.

ok but are we sure that is the NFB resistor?

Perty sure

what about removing it all together?

That would do the opposite. That would be like raising its value to infinity. If you keep lowering it you would eventually get 0 resistance which is just a jumper wire carrying back total NFB which would cut 95% of the volume and all the drive.

so ill try 10k then