help... my great cheddar sounds too good...

[marrstians]

so i built a great cheddar again using the ggg layout and schem... but i'm having a little problem... it isn't doing that little gatted blatty noisy sound on the position 4 like i remember it sounding... i can hear the trim pot changing the bias on the trannys, but i never get that classic gated tone.... what can i be doing wrong here? it sounds good and with total functionality on every other setting, and it seems to be trying to do what it's supposed to... but not quite there... any tips on getting that horrible tone?

[John Lyons]

Did you use the same trim pot value.
It's not getting misbiased enough I guess.


john

[marrstians]

using a 1k now, even tried a 5k to see if it would change the reaction more, but not at all... would changing the 10k resistor in that bias line, or maybe the cap give me a more extreme reaction? not sure what the culprit could be... but the pcb looks great, thanks :-)

[John Lyons]

What are the voltages you are getting on Q2?...
Well actually the range of voltages while in position 4
and rotating though the pots travel. Base Collector Emitter

[marrstians]

.79v-.85v
1.39v-1.43v
2.74v-4.20v

if i did those right...

[marrstians]

any ideas?

[John Lyons]

If that bottom number is the collector ( mistakenly said BCE instead of CBE) then you probably need a larger collector resistor
as the getting sounds you want are lower than 2.7v. Make sure that you put in the right values first though before you go tweaking it.

john

[alex frias]

Maybe a pot with a fixed resistor for external control of misbiasing?

[marrstians]

oops... yeah, i measured from the bottom of the of the board and forgot to switch the numbers when i did the voltages... looked back thru every thing and all the parts are correct on it... the only thing i noticed was that i accidentially pot a 5k pot on the fuzz knob instead of the 1k specified... but would this be causing my problem? if that were the case then wouldn't i get the right tone somewhere thru a sweep of the fuzz? not sure... but if it is the 5k pot that's the problem, i'm out of them   wasn't there a link somewhere on how to make a pot act like a smaller pot? i forgot where i put that one... any help in the right direction would be great

[John Lyons]

Yep that's the problem...
You should have a 1K pot in there for the fuzz knob.
That 1K resistance sets the operating point of the transistor.
That's why your voltages don't swing enough to get the gating sound.
Put a 1K resistor across the 5K pot and you should be able to get the sound you want back.
Use a resistor in parallel math/calculator to help you get close to 1K by putting a fixed resistor
across the outer lugs of the 5K pot. The total resistance measured across the outer lugs
should be close to 1K.

john

[marrstians]

DOH... you're right... i was thinking of a different type of pot setup was fine but after really looking at it, it all makes sense now... thanks... i guess it was a good learning lession when you're a bit rusty and try to dive head 1st into doing it again... gotta learn patience... but thanks a ton... i will enjoy my new pedal now