Wiring diagram help -Amp FX loop switcher

[blues_mang]

Hey guys, I could use some help on this. I'm just finishing up my new pedalboard for all my modulation pedals and have implemented a switch to route the signal from in front of the amp to the amp's effects loop. It almost works, but something's not right. When the FX loop section is chosen, I'm getting very low output...just barely audible, however when the opposite side is chosen, it works fine. Here's the diagram, maybe someone can point out an error or tell me that this won't work the way I have it wired. I'm using a dual-color LED for status as shown:



What do you think? In theory (to me, anyways) this should work, but my theories are sometimes wrong. Go figure!

Thanks,

BB

[oskar]

Your second loop isn't really in the soundchain...
Try this. It'll do the switching and ground the send channel that is not in use.

S=send, R=return

[blues_mang]

Oskar,
I understand what you are doing with your diagram, but problem is, the Send loop and Ret loop on my diagram is an amp series effects loop so the return shouldn't go to the output. It should just be making a loop with the effect(s) that are in the first loop. The input should go directly to the output when that loop is selected kind of like having the guitar direct to the input of the amp and just some effects in the amp's loop. I just want to switch where the effects are (in the effects loop or to the front of the amp) If that makes sense.

-BB

[oskar]

If that makes sense.

Ah! Now I get it. Send is in the first case from your switch and in the second from the amp... It should work.
Have you checked the switch for continuity?

Split the search up in smaller parts to see where the sound fails.
1. Is there sound coming from the fx send...
2. does it pass the switch. etc...
It's just like testing a circuitboard with an audioprobe but on a bigger scale.

[iaresee]

See this: http://www.diystompboxes.com/smfforum/index.php?topic=71183.0 -- I'm not certain it's always okay to share grounds on the loop and the preamp. Some say it works. But I'm suspicious it's always okay. I still haven't built this, but I will in the next week...

[blues_mang]

Oskar,
yes, I checked continuity on the switch. Everything checks out. I have sound at every position, it's just that when I have the amp's effects loop selected, the sound is very muffled. Just barely audible. But I can still hear the guitar and I do hear the effect that is in the loop. If I disconnect the switch and hook the guitar direct to the amp's input and put the effect in the amp's loop, it works fine, so I know that the effects loop is working correctly.

Ian,
So from that thread, it looks like I have to switch grounds as well... or at least the grounds from the effects loop? If so, then you're right, a 4PDT wouldn't work. Well, it would, but you wouldn't be able to use status LED. Hmmm....

By the way, this is for a Peavey Classic 30.

-BB

[iaresee]

Ian,
So from that thread, it looks like I have to switch grounds as well... or at least the grounds from the effects loop?

It's quite possible. There's any easy way to test this: take your switcher + effect and set it to put the effect in your amps loop. And then unplug and jumper, externally, the front-of-amp side of the looper. If that fixes the problem you have to switch grounds as well. If that doesn't fix the problem maybe you've got a bad wire in the box?

If so, then you're right, a 4PDT wouldn't work. Well, it would, but you wouldn't be able to use status LED. Hmmm....

Yea, you're in to something more complicated with Wicked Switches.

[blues_mang]

Aha! Ok, I solved this one after a little bit of reading of the amp's manual and some prodding with wires. Here is my findings: I found that when cords were connected to the amp's effects loop jacks and I selected the "effects loop" side of the switch, no problem, sounded good. Turns out, I was getting the muffled sound when I selected the switch to the "front of amp" side. Then I found that if I pulled the cord from just the return jack on the amp's effects loop, I got good sound on the "front of amp" side of the switch. A little flipping through the amp's manual and I found a very useful statement concerning the effects loop: ..the effects loop send and return jacks are shorted together internally when nothing is plugged into them (to paraphrase). So, while the "front of amp" side was selected and everything was plugged in, I touched a wire from the tip of both the send and return jacks and Voila!, perfect sound. So, grounding had nothing to do with it... the jacks can share ground. I just had to figure a way to short the tips of the effects loop jacks when "front of amp" side was selected. A little reconfiguring of the switch wiring and it still can be done with a 4PDT and have a status LED