Small Stone Piedrita Phaser is Back!

It seems like it's been an eternity, but in reality, it was April 29 - a little over three months - since I last worked on the Piedrita Small Stone Phaser clone.  When I left it, it was passing signal, but not phasing.  I had unsoldered some resistors while addressing the volume drop issue, and one of the pads on the board was gone, which meant a connection was missing.  I just ran a little jumper to fix it, and it works!

I had substituted a 10K resistor for R42 (stock is 4.7K), and that fixed the volume issue.  However, like everyone else who has done that change, I now had the screaming feedback with the color switch engaged.  So now I'm working on that. 

One solution I tried (see the pic) is a 10K trimmer for R11 (in the feedback loop) and a resistor and pot for R42.   In theory, this allows you to tune the feedback out with the trimmer.

However, this doesn't work for me - I still have feedback I can't adjust out.  And second, after studying the schematic more, I realized that you don't want to mess too much with R42.  Putting a pot there means you'd mess with the volume of the phaser in the non-color mode. 

So I'm going back to 10K for R42, and I'm going to try a higher value for R11 (was 3.3K stock, and clearly 10K isn't enough on my pedal).  Stay tuned.