[sdiy] TB-303 humming noise problem

[Gordon JC Pearce]

On 11/02/13 07:45, Paul Anderson wrote:
> My suspicion is that the LED is being driven using pulse width
> modulation, and that's what you are hearing. Can you post a link to
> the schematic? There's probably a capacitor nearby that is in a bad
> mood.

Not PWM but multiplexing, and you are hearing switching hash getting 
back into the audio (possibly because something is dragging the chopper 
PSU down).

Time to check those little disc ceramics, very carefully - now those 
capacitors *do* fail, frequently.

-- 
Gordonjcp MM0YEQ