To revive this mod again: I completed this mod about a year ago and have been very happy with the results, and again thanks to all that have contributed and reTrEaD helping me out with my troubleshooting issues. In order to pay it forward, I have attempted to add a little more to this design and submit my first mod.
I have not, as of yet, completed this additional piece but plan to do so when I get some free time. If the experts could approve the wiring diagram, which I copied directly from the original, I would appreciate it.
Now for the good stuff. I've attempted to incorporate what is typically referred to as Jerry Garcia's FX loop which he built into his guitars using dual-TRS output jacks. My mod for this adds only one TRS jack and keeps the original TS output jack. No need for 2 TRS jacks as I'm not including any of Jerry's on-board buffers/pre-amps. I figure this is accomplished easier in a foot-pedal anyways.
In addition to adding a TRS jack, one will need to purchase another push/pull pot for the 'Parallel' Tone which is used for this mod. Don't forget one would also need a stereo/TRS cable plugged into this jack and a new jack plate to accommodate two jacks.
I am a bit shocked to see that this "effect-loop" mod has not been incorporated into any of the other mods on here. It seems pretty cool/easy, and is kind of "genius" as others have put it, especially for Jerry to have thought of it in the 70's.
To those unfamiliar with this on-guitar FX-loop: The genius of this wiring is that it allows one to keep full volume going to the pedals while controlling the output volume from the guitar. The advantage is that the tone and response of the pedals would not change with the guitar's output volume, as it normally would if you plugged directly into them. The wiring also allows for a true bypass of the effects when they weren't in use.
Disclaimer(s): 1) I copied the John's wiring diagram completely and then added the mod. 4) I take no creative credit for this mod, only the incorporation of it into the SLOS mod. 5) Sorry for writing so much.
(N.B.: Earlier, I PM'd haydukej and requested that he re-post this from the Strat Lover's thread to a new thread for discussion. Thanks for doing so, haydukej, and Welcome Back to the Nutzhouse!)
Your addition of the FX loop should work. But there was a reason that Jerry used an active preamp/buffer in this type of a set-up.
By running the FX loop out of the guitar passively, and then back in, you will be adding the cable capacitance of the length of cable to the pedals, through the pedals, and back into the guitar. That added capacitance will suck the tone out of your pickups.
Using one or more buffered pedals (i.e., non-true bypass) will help from the pedals back in to the guitar, but the run from the guitar to the pedals will still be a problem.
Well thanks for the heads up. I was hoping to get around not using a buffer. I'll have to think about how bad I really want the fx loop or if I can even fit that buffer in my current setup. I've done some research and it seems like a simple enough circuit to build myself, especially since some people are trying to sell it for $70.
I think I know the answer to this, but placing my JHS mini bomb boost as the first pedal in the chain still wouldn't solve the problem would it, seeing as how that's a JFET boost and not actually a buffer?
I don't know what the JHS pedal is, but any non-true bypass pedals will buffer the signal, even when "off". AFAIK, all Boss pedals do this.
The issue of cable capacitance is one of the reasons why "true bypass" isn't all its cracked up to be. There's a good article somewheres on that topic, I don't have the link handy but if you google "The myth of true bypass" or something similar you'll find it.
Our own JohnH has diagrams for a simple JFET buffer circuit that would fill the bill for what your doing:
Of course, with an active circuit, you'd probably want to go wiht the 2 TRS jacks so that the output jack can be used to cut the 9V battery.
Also, you have the issue of using a stereo cable out of the guitar (and back in) for the FX signal. I think Garcia had a special box to take the stereo signal and split it into in/out for the pedals, then back into the guitar via the other connection on the stereo cable (sharing a common ground, obviously)
I think we need to clarify for non-participating readers here - the reason for two TRS jacks is that one will carry two of the three signals involved, and the other will take care of the remaining signal and the battery power (Ring to ground, the standard method). Also, this modification needs an additional "breakout box" to separate the signals carried by the stereo cable used with the two-signals jack.
Excepting the battery power switching, the signals can be arranged to suit one's preferences. However, if you wish to use the guitar without the FX loop, you'll need to consider which jack should have the tip as the Output signal that will go straight to the amp. I'd personally prefer that to be the one with the battery power, so that the buffer is on all the time - that way there's no loss of Tone from using a longer (or lower-quality) cable.
Also, in all of this remember that there will be only one stereo cable (two conductors with a shield) - the other will still be a standard guitar cord. But it would be my advice that you should carry at least one spare stereo cable. No matter who made it, it's still subject to wear and tear, and you all know how Mr. Murphy feels about that one, right?
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