Stuff you wanted to know but were afraid to ask

I'm asking this AFTER a long, involved thread many months ago, but... I'm still not quite sure how to best connect power to a Muffin Crumb Amplifier or Tone daughterboard... Seems like you could just take a second wire from the DC Jack, but it was mentioned before that this would bypass any protection circuitry.

This is a VERY stupid question considering that these are you-pick-the-values utility boards for various situations, but... I'm also not really sure where to start when it comes to choosing values for either the Tone or Preamp/Clipping/Recovery blocks. First time using this kind of add-on.
 
If you're adding it to an existing build, tap 9V from the cathode of the main PCBs polarity protection diode.

If you're using it standalone (probably not) use a 1N5817 diode instead of wire to connect the positive lug of the DC jack to the PCB.


As far as the values, start with values from one of the Muff variants.
 
Robert said:
If you're adding it to an existing build, tap 9V from the cathode of the main PCBs polarity protection diode.

If you're using it standalone (probably not) use a 1N5817 diode instead of wire to connect the positive lug of the DC jack to the PCB.


As far as the values, start with values from one of the Muff variants.
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Gotcha, thanks much! I believe this is what @jwin615 had mentioned, but I got caught up in an alternative method of flying a cap and diode off of the actual Crumb if going straight from the DC Jack... If tapping the cathode of the pcb’s protection diode won’t cause a loop that seems much easier.

I’ll definitely take a look at the various Muff variants, that should help with the Tone Crumb for sure. The Preamp Crumb seems a little trickier to determine possible values, especially since it can do a few different things. Maybe looking at Muff schematics will help with that too?
 
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Thought I made a screenshot or saved bookmark about killing oscillations, supply and RF noise in pedals so could someone help me out fill this quick list?

  • 100nF cap from power jack positive lead straight to case
  • feedback cap between OPA output and - legs and hpf cap on transistor BC legs
  • Star grounding
  • Isolating cable jacks and only one gnd ref contact to case
And I know I’m missing one trick. Thought I made a bookmark or screenshot about it, but cannot find it. But it may have been a few hunder pF cap between input or output jack leads?
 
Robert said:
Why do folks ask to have random objects/animals drawn on their packing slip?
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mostly to see how far you will take it so they can have their viral moment should you go above and beyond ... like those posts of people who asked room service to decorate their room with pictures of Jeff Goldblum
 
ICTRock said:
mostly to see how far you will take it so they can have their viral moment should you go above and beyond ... like those posts of people who asked room service to decorate their room with pictures of Jeff Goldblum
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Yep, this. Some people don't care about imposition.

Btw, could you come to my house and give me a foot massage. Thaaaaanksssss....
 
How should I read symbols on a schematic, where no pin is specified, the symbol appears symmetrical, but directionality is important for pins? In particular, I'm wondering about pots and JFETs. Here's some example pots to show what I mean:
1735937206322.png

1735937357412.png
PPCB schematics, and other more recent ones I've seen, will specify the pins pretty clearly. In the first case I'm pretty sure it's pin 3 at the top and 1 at the bottom, since that seems standard for volume. But I'm wondering more generally.

And here's the JFET:
1735937406602.png

My understanding is that for JFETs the drain and the source can mostly be used interchangeably, so I suppose from a schematic perspective there's no difference. But for transistors where pin 1 is drain and pin 2 is source, you can't easily convert the schematic to a PCB without some pin wrangling.

Am I missing something?
 
I don't know that there is or was a standardized way of specifying which leg is which on a potentiometer on a schematic. If you know how the pot behaves either increasing or decreasing resistance you can figure it out (using legs 1 to 2 increases resistance, using lugs 2 to 3 decreases resistance). Legs get jumpered so that if the wiper fails the circuit can still function somewhat as if the pot is just a jumper on that portion of the circuit. On something like that speed control you'd have to know whether increasing speed would mean increasing the pots resistance or not.
 
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