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I guess my question, as someone that barely knows how clipping diodes work, is: will I ruin a part around these diodes if I tinker, or is there a range of forward voltages that I should be staying within to ensure the 914s remain intact and I don't blow out the ic ?

Tinker away, you can't hurt an IC by swapping out passive parts.

FYI, LEDs have a very high forward voltage (~1 to 3 V) compared to silicon (~0.6 V) and Ge (~0.3 V).  In a feedback loop, LEDs give you more gain; in clipping to ground, LEDs will give you less clipping and more output volume. 

The D9V I/V curve is very close to the 1N34A, and it's Ge as well.  BAT41 has a slightly higher Vf as the current rises, and it's the closest Si diode as jessenator says.  1N5817 has a significantly lower Vf than any other diode I've measured except Russian D310 and D311, it's about half the Vf of a 1N34A.  So in order of similarity to 1N34A, I'd try D9V, then BAT41.

Doesn't matter, since you'll be installing a non-polarized cap.  Strap one out, and replace the other one with your 470nF.

From the Setback build doc:

If you don't want the Tails switch it's easy to defeat. Simply solder a jumper between the TLS1 pads on the PCB. Leave the TLS2 and LED2 pads empty. You can also omit R16 and R17 in this case.

You'll still want to block DC from the NE570 pin 11, but instead of equipping both C9 and C10, you can strap one of them, and replace the other with a 470nF non-polarized cap. That's assuming you omit both R16 and R17. 

IC01 is an OKI MSM5819.  Here's view inside it, from another turntable that uses the same chip in a similar way to control the speed, although voltages are different (Yamaha PX-3).
 
It looks like pin 10 is an output of the MSM5819, nominally 3VDC, adjusted by R101.  If R101 is clean and working OK, and you have a wiggly voltage on pin 10, it's likely coming from the chip.  Inputs to this pin include the 6.144 MHz oscillator on pin 17, and pins 1, 4, 11 and 12.  I would:
1. Check the oscillator frequency which should be 6.144 MHz.  If it's wiggly, replace it.  If it's OK,
2. Check the voltage on the other input pins that are called out on the schematic: 1, 4, 11 and 12.  If any of these are off (unlikely), trace back to the source.  If OK,
3. Replace the MSM5819.

Sounds like fun!  We can't hurt it, and we just might help.  Bring it on!

I find that the guitar, the pedals and the amp all interact, and it takes experimenting to find the right combo.  And, a pedal that's perfect for a Tele and a Marshall can be absolutely horrible with a Les Paul and a Fender Twin.

I would suggest two things.  First, start with one guitar straight into one amp, and set the knobs in a way that sounds good to you.

Then add one pedal, and work with the settings on the pedal without changing either your guitar or amp.  If you can find settings that you like, mark them on the pedal or write them down.  If you can't, set the pedal aside and move on.

Put another pedal alone between your guitar and amp.  Same process.  Find the sweet settings, or set it aside.  Continue until you've tried all your pedals, one at a time.
 
Second, work on the sequence.  Take your two favorite pedals and find a sequence that works, again without changing your guitar or amp.  Make notes.  If you can't make them work together, set one aside and try another pair.  Once the first two are good, add in another pedal, etc.

If you have other guitars or amps, same process with each one.

This should lead you to (1) a set of pedals that work individually and together, and (2) a sequence that gives you sounds that you like.

You will likely find one or more pedals that just don't sound good with the rest of your setup.  Use them with a different guitar/amp, or sell them, or give them away.

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Levy's Leathers has a great selection, and up to 4.5 inch widths.  +1 on a wide strap with a suede back, I don't think padding will help much. 

This is the Cardinal build doc from 2013, and the schematic inside is labelled V1.4.  Gotta love that Wayback Machine, you can find more 1776 FX history at https://web.archive.org/web/20140415000000*/https://1776effects.com .

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Where the 910k and the 10k join is where your V+ should connect. 

Thanks for posting, Bean, we all go thru dark places from time to time, and just saying it out loud can help.  I appreciate all you do for us, both here on the forum and thru Madbean. 

On your original question: Something like an Alesis Micro Gate might be a good starting point.  One of these in a "Y" connection with your main signal chain could open the gate to the second branch of the "Y" at a certain signal level.  It wouldn't suppress your primary signal chain, but the secondary branch would be silent until the signal level threshold is hit, and return to silence when the level falls back below the gate threshold.  Or, you could run a separate signal in/out of the Micro Gate and trigger it with your primary signal source level. As a bonus, they're inexpensive and stereo, the two sides trigger together but signals are independent.
Manual: https://ia802808.us.archive.org/5/items/synthmanual-alesis-micro-series-owners-manual/alesismicroseriesownersmanual.pdf

After that 47k, there are two loopback paths, one to the gain pot lug 2, and one to the output of IC1.  I'd check everything in those paths, if the signal is good up until the 47k.  IC2 could also be faulty, try pulling it and see if the signal is good all the way up to it's empty socket.

The power on IC1 and IC2 are correct, IC1 runs on +9V and ground, while IC2 runs on +18V and -9V for more headroom.  The voltages on IC3 also look OK. 

I think the key is that the output is low both during bypass and when it's active.  That narrows it down to the following, which is the buffered bypass path, along with the foot switch wiring.  You might want to use an audio probe to see where the signal falls off.

• input jack
• 2 resistors and a cap on the input side of IC1
• IC1 which is the buffer
• 4.7u cap, 560R and 100k resistor in the bypass path (unlikely)
• 68k and 100k resistors at the output
• output jack