Noisy germanium circuits.

[druz15]

So I'm breadboarding a Rangemaster circuit using NOS Germanium PNP trannys.

I'm using a modified version of the circuit that allows you to power it from regular 9V PSU, but when my charge pump polarity inverter bits arrive I'll probably build to the normal schematic.

I know it's a famously noisy circuit but this thing is fucking noisy. I'm not talking hiss, I'm talking high pitched screeching that happens whenever you stop playing, that's almost as loud as the signal itself.

I've got a 100uf cap going to ground from the 9V, it's a good PSU (one of the ones you get with strymons, but will eventually be running it from my MXRCAE powerboard)

Apart from switching the resistors to 1% metal films which I'll be doing next, what else can I do to tame the noise?

Better filtering on the supply rail? Bigger or smaller caps? Or a LPF in the circuit to cut everything above 20kHz maybe?

any suggestions?

EDIT: I thought it might be a bad transistor but I swapped out a few different ones with different HFes etc and the problem was there for all of them,
there was even noise with no transistor socketed (obviously the circuit isn't passing audio at that point which suggests the noise is either on the supply rail or the output section)

schematic I'm working from is this one
http://www.tonefiend.com//wp-content/up ... %20v03.pdf
PAGE 8, with filtering added to the supply rail

[alanp]

http://madbeanpedals.com/projects/Range ... er2014.pdf

Try breadboarding that one. The -9V is coming from pin 5 of the IC, so you can strip all that back if you don't have the IC on hand. It's only to change the +9V to -9V, anyway.

[druz15]

yeah might try that.

Correct me if I'm wrong but if swap the 9v and ground terminals on my breadboard, that is essentially a positive ground power supply no?

So I can do that to test this running on -9V and then when I get a charge pump inverter running it'll behave the same way.

My Power supply is actually isolated so I don't technically need to run an inverter, but this saves me from having to use a polarity switching cable

[druz15]

ok breadboarded that, still got noise. Turns out it was the Damage Control / Strymon wall wart. Noisy fucker, but quiet as with timeline etc, must be something to do with the digital crap in the strymon.

Anyway got it working. Sounds fantastic, Rory, Brian & Jimmy in a box. New secret weapon, happy chappy

[alanp]

Wonder what the basic design of it is. Linear PSU's are better for pure analog (no switching noise) -- this is why you don't use 1KW ATX PSU's in your analog synth, even if it does have 12V at a zillion amps.

[TmcB]

ok breadboarded that, still got noise. Turns out it was the Damage Control / Strymon wall wart. Noisy fucker, but quiet as with timeline etc, must be something to do with the digital crap in the strymon.

Anyway got it working. Sounds fantastic, Rory, Brian & Jimmy in a box. New secret weapon, happy chappy

Hahaha I have been nailed by this exact problem before!

I was putting in all sorts of power filtering and it turned out the Strymon wallwart is a total piece of shit. As soon as I hooked it up to something good, it worked perfectly.

Also watch the type of chip you get for the voltage inverter, some will bring in high pitched oscillation if you get the part number wrong.

[druz15]

ok breadboarded that, still got noise. Turns out it was the Damage Control / Strymon wall wart. Noisy fucker, but quiet as with timeline etc, must be something to do with the digital crap in the strymon.

Anyway got it working. Sounds fantastic, Rory, Brian & Jimmy in a box. New secret weapon, happy chappy

Hahaha I have been nailed by this exact problem before!

I was putting in all sorts of power filtering and it turned out the Strymon wallwart is a total piece of shit. As soon as I hooked it up to something good, it worked perfectly.

Also watch the type of chip you get for the voltage inverter, some will bring in high pitched oscillation if you get the part number wrong.

Yeah I was just using it as it's the only wall wart I have lying around these days.

Thinking I might give the inverter a miss actually, I've just wired the +9v and ground the other way round and it works fine off my power supply, so shouldn't have any issues. Will do it for the 3 knob tone bender I've got planned though, as I might need to use that in a daisy chain at some point