Vintage Mistress ticking

[yeeshkul]

Yes, i did the star grounding. I may try two decoupled power sources , however the pedal is quiet now, so nothing really pushes me in that direction.

[yeeshkul]

I see it now in the photo.  A big fat wire going to the light blue section. Seems the light blue and dark blue sections are directly connected after all.
That means that although you have a star ground, you don't in fact have separate decoupled supplies for the audio and LFO/VCO sections.  You really have a single supply node and a single ground node, with a lot of capacitance between those two nodes.
It just happens to be distributed over the board.

Actually not. Look at the schematics image above the pictures - it is done just how you suggest it. On the image, i have shorts instead of 10R filtering resistors as i wasn't sure what value would be the best.
One of the filters is "sideways", because i am filtering noise *from* VCO that can get to signal part via the DC  path.

[DrAlx]

Separating VCO supply from audio supply in the hope of stopping VCO (clock) noise from affecting the audio is pointless, since the VCO signal is actually operating on and affecting the audio ***within*** the BBD itself.  E.g.  if you amplitude modulated the clock pulses, that would carry across into the output from the BBD, and no amount of supply separation would fix it.  I wonder if anyone has deliberately amplitude modulated the clock pulses to produce an effect

LFO tick noise is another story. You can give the LFO its own filtered supply, but to be honest I have found what helps the most is to keep the wires to the rate pot (which are often directly on the square wave output of the LFO) as short as possible and as far away from the audio part of the board.

[sebtux74]

Dear yeeshkul
What is the name of the software to draw this nice veroboard:

Thank you

[yeeshkul]

Paint Shop Pro 7.

[sebtux74]

Thank you

[miketbass]

I have just finished repair on a 1977 V2 version of this, the board appears to have all of the factory mods to the voltage regulation and supply filtering (seemingly installed at the factory judging from the components and shoddy soldering) and it is about as quiet as one would hope for. Compared to my same year Clone Theory w/SAD1024 this is whisper quiet.

Here is a component side shot of the pedal in question. After replacing the voltage regulator transistor I measure 12.2v on the supply pins. Clock frequency measures from 22khz - 220khz measured at the SAD1024. This particular unit was supposedly owned by Joe Satriani at some point - I have the pawn shop sales sticker to prove it!! lol

Anyways for anyone wondering what EH may have done in house to "mod" this circuit for lower noise I believe the attached photo captures it well.

[yeeshkul]

Thank you. The only unusual part i can see is that black elyte cap. The two greenees are quite usual, i had to add those to my unit, but i wouldn't say it really helped.

EDIT: actually the black elyte cap is a standard part, just soldered on the bottom of the pcb.