x0x #2 Finished: Faint Note Noise after Note is played Moderators: altitude, adafruit_support_bill, adafruit, phono, hamburgers

[A388Flyer]

First x0x went off without a hitch... had to do a bit of debugging on the second one, but it's 99% done.

The one problem I'am having is that after playing a note, if I turn up my volume really loud I can hear the note still being played very quietly... the sounds reacts to the VCF and tuning knob, so there is still some oscillation going on.

Thought it might have been Q39 base which shows around 27mv when not playing, but my first x0x (without this oscillator issue) shows the same.

It's not a major nuisance, but it's just "one of those things" you want to try and fix. Any advice on what to test and try to track this bug down is appreciated.

[Jaytee]

Sounds like maybe the VCA isn’t closing completely.

[A388Flyer]

Thanks for the reply. I swapped out the BA6110 in case that was faulty, but no dice

I then probed Pin 4 (Control) on the BA6110 and while my first x0x shows around 0.1-0.2V the x0x that is letting the oscillator through with note off is showing around 0.8V. Can't remember the Q number of the transistor feeding it, but I am wondering if the 733Ps I purchased from UTSource are bogus?

The voltage measured on the middle (Collector?) pins on these "733Ps" seems to be much higher than the voltage reference chart, although the outer pins seem to be in accordance with the chart.

[A388Flyer]

Tried swapping out Q31 (since it signals Pin 4 of the BA6110)... same thing, these 733Ps must not be legit and are letting out more voltage through the collector than they should.

Is the KSA733 a good secondary option (I see Mouser/Digikey have them)... I admit I am really green on transistors, such trying to figure out what will close the gate to the BA6110 properly.