Bypassing an effects loop?

[rspst14]

Hey guys, I'm wondering if there is any way to bypass an amp's effects loop.  I have a couple of non-true bypass pedals in the effects loop of my Peavey Classic 50, and I'd like to be able to get as clean of a signal as possible when I'm not using these pedals.  I can easily bypass the pedals in front of the amp using a true bypass box, but is there any way to switch the effects loop in and out?  I have a two button switch for my amp, with one button switching channels and one button turning the reverb on and off.  Since I leave the reverb on all the time, is there any way to modify the amp so that the second button turns off the effects loop?  I realize that I could always use another true bypass box, but that still leaves some longer cables in the effects loop.  I play without effects a lot, but it's nice to have those pedals for certain things.  I'd like a setup where the signal from the guitar travels through the least amount of cable as possible when I'm playing without anything turned on.  Is there any way to do this, or is it just not possible to turn off an effects loop like this?  Any help would be appreciated.  Thanks.

Ryan

[Chris S]

Hi Ryan,

My hunch is that the the output or input from the amp will have a stereo jack on it (tip ring sleve). A normal guitar jack is (tip sleeeve). My suggestion for by passing the effects is build a little box that between the effects loop and the input or output of the amp effects loop (sorry not sure which it will be) plug a stereo lead into the amp and the box. Then get the box to.

A. Connect the Stereo sleeve to the mono sleeve and the stereo tip to the mono tip and leave the ring unconnected. - this will turn the loop off

or

B. Connect the Stereo sleeve to the Stereo ring and the mono sleeve the stereo tip to the mono tip. - this will turn the loop on

My hunch will be that it is the amp loop input that you will need to do this to.

Alos I have a Peavy 50 Classic, I thought that if you plugged a effects unit in the loop then the dirty to clean footswitching switch then became your effects on off switch.

Chris

[Peter Snowberg]

That should be a fairly easy mod. First... have you seen this page? http://www.blueguitar.org/new/articles/blue_gtr/amps/peavey/c50_origmod.pdf

According to the schematic at Steve Ahola's site http://www.blueguitar.org/new/schem/peavey/modnotes/c50twdbm_sch.pdf the reverb is switched on and off via a JFET. It looks like you could freeze the reverb on all the time by removing R31 on the main board and installing a jumper across C31. You might want to make that a toggle switch instead of just a jumper but either way it looks like jumper installed = reverb on. OK. You could then copy the channel switching logic (12V relay, 1N4001 or 1N4148 snubber diode, 22uF/25V cap, and 470 ohm resistor) with the switching connected to the side of the old R31 position (marked 2 on the schematic) that connects to J33. Break the line from the effects return jack and use the relay to switch the line between the jack's tip connection and the switch connection in the jack that would be shorting to the tip with nothing plugged in. Presto.

I can elaborate more if you can find a clearer schematic for me to draw on.

Take care,
-Peter

[rspst14]

Alos I have a Peavy 50 Classic, I thought that if you plugged a effects unit in the loop then the dirty to clean footswitching switch then became your effects on off switch.

Chris

Thanks Chris.  I haven't tried the switch with anything in the loop, as I'm still getting my pedalboard together at the moment.  One button is labeled "select/effects", and the other is labeled "reverb."  Peavey uses that same footswitch for a couple different amps, I just assumed that maybe another amp model was designed to allow you to switch the effects loop in and out.  That would be kind of inconvenient if putting something in the effects loop meant that you couldn't use the footswitch to switch channels.  I'll have to give it a try and see.

Ryan