Wiring for Paramix between two circuits

[Anonymous]

Hi there,

I’m looking to put a Paramix circuit in between a preamp and a cab sim in one box, so it will go pre amp->paramix->cab sim.  Essentially, I’d like the paramix to act like an FX loop in an amp, with a wet/dry blend.  I will be using three different 3PDT switches with true bypass on each circuit inside the box.   I’ve never put 3 circuits in a box before, and I’d like some advice on the paramix offboard wiring specifically related to grounding and not creating a ground loop.  I can see where input/output “tip” signals should go so all good there.  However, in the Paramix build doc it looks like there are extra ground pads from both the “In” and “Out” sections of the PCB that are grounded to the sleeve of the jacks, in addition to the main ground pad next to the +9V.  In my build, the Paramix circuit and bypass switch won’t be connected to an input and output jack, as it will be sandwiched between two other circuits.

My goal for the 3 circuits is to star ground everything to the DC jack sleeve via the main input jack of the pedal.    So circuit 1 (preamp) will be grounded via it’s PCB ground pad and the input jack and circuits 2 and 3 would share those grounds according to Madbean’s dual circuit wiring except with an extra circuit in the middle.  I’m fine with keeping the specified Paramix build doc bypass switch wiring the same, fwiw.  I just need to know where to connect the ground from circuit 1 (preamp) to which pad/location in the Paramix wiring scheme, and which location to take a ground from Paramix’s circuit to circuit 3 (the cab sim) without creating a ground loop.   Can I bring the ground from circuit 1 to the Paramix “Ground” pad, connect the ground from the Paramix “In” dual pad to the Paramix’s 3PDT bypass switch, and then take a ground from Paramix’s “Out” dual pad to circuit 3?   How do the ground pads that are part of the dual pads for “In” and “Out” relate to the overall “Ground” pad in the power section for the Paramix PCB?

Thanks!

• Dan

 

 

 

 

[Anonymous]

Well, let’s play the “KISS” game!  Ground is ground for all of the points you discussed.  You can take any ground point and attach it to any other ground point and even continue the connection to other ground points.  The important thing is ALL BOARDS, JACKS, ETC. MUST be connected to a common ground.  It does not need to be a single “STAR” ground point.  That type of grounding is primarily used in amplifier designs due to the high gains involved.  Ground loops are mainly an issue with connections to different amps, mixers, etc that have longer cable runs and use different power connections.  Inside pedals, ground loops are not an issue.  So, keep it simple and just make sure every board, power supply and jack have a ground connection.  I hope this helps..

[Playsforfun]

Hey Dan. In addition to ‘The Great One”s good news I’ve got a little too. I found as I built, especially combo pedals which I love, there are ground pads all over these boards. Many are available for exactly what you are wishing for. And the more you cram in there the more sharing of ground points there can be. One example for the paramix could be that when you are boxing you discover that to ground both P1 and P3, you can jump between the two pots and then to a single pad on the board. You just freed up the pad 1 of the ‘jumped’ pot. It happens when you don’t use the LED pads for an LED also. They are all over the place and you will find them more and more as you build. And if you use the 3PDT boards, well, now you have close to a zillion ground pads available. Have fun.

[Anonymous]

Hi Wilkie, playsforfun,

Thank you both for taking time to write up helpful and thoughtful responses.   I think I was feeling a little intimidated by trying to make all of the switch wiring work as a somewhat intermediate builder.  But the advice from both you is great, and I think I was overthinking the grounding.  But the additional info is helpful in making sure I can approach future builds more confidently, too.    When I get the whole thing working, I’ll make sure to do a build report.
I really appreciate the help!

Thanks again,

– Dan

 

 

 

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