Hi,
I've recently put together a pepper shredder and sugar box and I am having an issue of high frequency oscillation in the 10khz - 16khz range and I'm looking for some help with troubleshooting it. The frequency of the oscillation changes when the volume, gain and bass control are changed and when the output voltage from the charge pump is changed otherwise it seems unaffected by changes to the input or output load.
With the sugar box if I boost the voltage from the charge pump I can make the oscillation disappear above 22khz making it inaudible but the starting frequency on the pepper shredder is much lower making this solution not work for the pepper shredder. Ive checked all my solder joints and cant see any issues. Ive tried multiple power supplies rated at 3A, 1.5A and 1A and although there is a shift in frequency when the power supply is changed non of them solved the issue. I've also had a poke around with an cheap oscilloscope and I cant find any obvious issues or where the oscillation is starting from.
Although I've put together plenty of electronic circuits this is my first tube project so I am fully expecting this to be a user error issue that I'm just not seeing so any advice is welcome and I'll happily answer any questions.
Thanks in advance!
Michael
