Wiring the C-Buffer as a standalone unit

[darwin999]

Clearly, PedalPCB's C-Buffer (a.k.a., the Cornish buffer) is designed for being used together with an unbuffered effects PCB within the same enclosure, and for that use case the PCB & switch wiring instructions are straightforward and clear.

But what if you want to use the C-Buffer PCB as a standalone unit, in it’s own enclosure? For this situation, there is an ambiguity in the PCB labeling that may get in the way for some builders. So I thought I would write up how to wire it standalone, just to remove any possible ambiguity - particularly for new builders.

There are 2 key diagrams in the instructions: (1) the schematic, including the 3PDT switch


plus (2) the PCB assembly. Here I’ve added the labeling on the actual PCB (in red).


The ambiguity comes from the various in and out labels - i.e., IN, PCB_IN, OUT, and PCB_OUT – which are clearly labeled on the schematic.

However, the actual PCB itself has two IN labels and two OUT labels, i.e., nothing is labelled PCB_IN or PCB_OUT. And it’s also not initially obvious how to wire the PCB for standalone use. (Yes, I know, if you are an experienced PedalPCB user and think for a moment, you can figure it out along with some DMM measurements for confirmation.)

So for clarity, here’s the my relabeled PCB image with hopefully less ambiguous labeling:


And here’s how to wire it in a standalone enclosure, along with an LED:


I hope this may be helpful to some builders.
Cheers!

 

[keevohn]

Thank you! Dumb question, but do you still need the 3PDT switch in this scenario? If so, can you jumper the switch pads to eliminate it?

 

[darwin999]

do you still need the 3PDT switch in this scenario? If so, can you jumper the switch pads to eliminate it?

Not a dumb question at all. You definitely could shift to using a DPDT by giving up the LED, which (as shown by the 3PDT switch wiring diagram below) connects to the center vertical column of switch pins (i.e., B). Hence you would have to give up soldering the C-Buffer switch pad directly to the stompswitch, as the in and out wiring goes to the outer vertical columns (i.e., A and C) - and instead use wires to connect the DPDT switch pins to the PCB.


Here are the switch pin labels for the PCB - note the left vertical row is labeled C (not A) because this is the underside of the PCB. I.e., in normal use the PCB is turned over and then soldered directly to the 3PDT switch.


Note that *if* the PCB was instead wired so that the LED and SW pins connected to either column A or C, and thus IN and OUT were on adjacent pin columns for the 3PDT - then you could solder the DPDT switch direct to the PCB for IN and OUT connections (leaving the LED/SW pins unconnected). However the PedalPCB standard format has the LED in the center of the switch, which (I would think) is likely a good idea in order to keep IN and OUT wires well separated to avoid capacitive signal pickup between them.

I hope this makes sense - feel free to ask more questions if it doesn't. Cheers!

 

[keevohn]

Thanks for the explanation. I'm hoping for something even more basic - no switch, just an always on buffer in a minimal enclosure.

I just found this diagram in another thread. I think this is what I'm after?

This should work, The white circle & cross is an Adhesive Standoff
Confirmed with Mr Pedal PCB :

View attachment 3258