Preamp / FX loop switch

Started by Alien8, November 15, 2007, 03:34:27 PM

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Alien8

Hi Everybody!!  I'm a newb, and am really happy to see the amount of information sharing and assistance provided on this site.  Kudos to all!

Anyways, I was in another thread asking a question kind of related to that subject, but thought I should maybe start my own, since it is its own topic.

Basically I would like to be able to switch out my delay pedal from being in front of the amp to the FX loop with a stomp switch.  I've got a diagram of what I think will work, however I do not understand what to do with all of the gound wires from each jack.  Since I would have a connection made from the input of the amp to the fx loop, I thought that would be a bad thing, and would require some isolation.  Here is the drawing:



My question is:  Do I need to isolate the grounds in FX loop from the EFX chain?  Then, if I do need to isolate the grounds do they need to be switched as well?  Ie... switch the guitar ground from the EFX chain directly to the output when the EFX chain is in the FX loop - which would also mean that the grounds of the FX loop send need to be switched to the EFX chain, and back to the FX rtn when not active?   Undecided

Alien8

Does anyone have any ideas, or places to point me to go in the right direction? 

Alien8

While at the local electronics store on the weekend I found an 8 pole 3 throw rotary switch  :icon_lol: that should cover me to begin this project...  and for only $4 CAD  :icon_eek:.  The bonus of this is that I can add an LED quite easily now  :o!!

After much research on the weekend and some simple road map drawing, I have come to the conclusion that all signal grounds will be isolated from one another, and switched with the signal.  This should keep the two signal "highways" separate from each other, unless I want them to be by turning the switch... Just like a switch track for a locomotive really.

I also decided that a foot switch is not required for my purpose... 


  :icon_idea: On a side note, I've come to the conclusion that the only method to really accomplish a switch between a Preamp and an FX loop would be to route all grounds with the signal, thus switch the signal grounds with the signal.  You would either need to find a 6 pole 2 throw switch, and use the diagram above to route it (3 poles set-up for signal lines / 3 poles set-up for signal ground lines), or use some type of CMOS chip, and electronically switch the same routing.