Muff’n, Green Russian, why do I have low frequency noise

[Anonymous]

Hello brains trust!

So I have been finishing off my muff’n and after some wrong wiring, dropping the wrong pots in the wrong positions (who would have thought that there both were log and linear pots in this build?!), checking values and a bit a resoldering. I have finally got to a point where the pedal is basically working but I seem to have this low frequency rumbling noise in the background that is not doing great things to my bass amp speakers. I have yet to get the oscilloscope onto it to see exactly where it might be originating from but was wondering if this was a common issue and if it was an easy fix? The bypass is dead silent, so it is only when active that it happens. The diode switch also seems to make no difference either, should I expect much of a difference in sound between the LEDs and the regular diodes?

 

 

[Cybercow]

The first thing I see worth questioning is the orientation of the BJTs. What BJTs are you using?

I’m unable to make out any of the wiring due to the spaghetti bowl you’ve got there. :O

But is the input jack tip going directly to the main board input? Double-check the tp/sleeve of the jacks too. Again, the spaghetti makes the wiring difficult to follow.

[Anonymous]

I can’t believe you are having a go at my spaghetti art! I mean it may help you actually see what is going on but still ????.

In any case your response did prompt some further work. I found a 30hz 50mV p-p on the output of Q3 (with no input). I couldn’t see it on Q1 though. My oscilloscope was being a bit weird with its voltage measurements so I ended up checking a few different power supplies. Couldn’t work out why the oscilloscope was weird but I ended up swapping power supplies on the pedal and the low frequency hum has gone! Turns out cheap internet power packs are rubbish. Still tracking down the diode issue but will add a better picture or two to help with that….stay tuned for the next incredible episode….

[Author]

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