Best practices for diagnosing signal chain problems?

[stevejamsecono]

Hello Folks,

Was unsure where exactly to fit this topic since it addresses a few areas (amps. effects, etc.), so hopefully here is best --

I have a somewhat complicated rig. I'm running a 4 cable setup into an amp head and small pedalboard that puts half of my effects into the loop and half out the front. I mostly use my amp gained up with my volume knob for cleans, so doing this was essential in order to keep my delays from getting out of control. When this works as intended, I'm very fond of the sound I get and feel very inspired. It's a setup I would like to keep. When it doesn't (as it has struggled with inconsistently over a brief tour this past weekend), it can be incredibly frustrating and difficult to diagnose in the moment.

At key parts of a few of our sets over the last week, it felt like the signal strength going into the amp weakened noticeably, making for a quieter, less gainy sound. The first time this happened I took my stuff home and painstakingly took it apart, tested all the cable connections in a sort of DIY way (i.e. plugging them individually into an amp to see if they got sound, then wiggling them back and forth once plugged in to see if they cut out at any time), and then reassembled my rig. I played a bit, everything seemed fine, and off to the next gig. The setup held up fine for another two shows before I started to notice this happening again at the last set. At first it seemed to be a loose power connection on one of the pedals, but once that was fixed it happened again if slightly less dramatically this time.

Obviously it's quite stressful to think this could happen at any time, but I'm at a bit of a loss of how best to diagnose it at this point with so many potential points of failure. I feel like I've accounted for most of them, but it's hard to tell which is doing what in a moment with my current level of knowledge. Suspected culprits are --

- My cables? - Unlikely as I just tested all of them and they seem work.
- Power supply? Possible, but my CIOKS DC5 has run wonderfully for a long time and I'm not overtaxing it as far as I can tell.
- Junction box? Possible. Would I need to replace it with something more robust, perhaps built into the pedalboard?
- Amp Power Tubes? Possible, but I did just replace them. Do they burn out more quickly because I'm using amp gain?

Any advice/ideas on handling something like this? I would STRONGLY prefer to keep this setup together as I've never sounded better, imo.

[marqueemoon]

I would spend some time with guitar>amp, then slowly add things back starting with effects in front of the amp.

After that maybe you could even install just a patch cable between the in and out of the effects loop to see if the loop itself is giving you trouble.

[JSett]

Just process of elimination.

Just cable & guitar?
Just guitar and pedalboard (out front) on its own
Just guitar and loop pedalboard together

This should narrow it down considerably. Once you've ascertained which 1/3rd of the rig is playing up then you can dig deeper into that part.

I bet it's a cable. It's almost always a fucking cable.

[stevejamsecono]

I would spend some time with guitar>amp, then slowly add things back starting with effects in front of the amp.

After that maybe you could even install just a patch cable between the in and out of the effects loop to see if the loop itself is giving you trouble.

Yeah that might be a solid move. Gonna fly by the seat of my pants for the gigs because I just need all this stuff for those, but once we get back to rehearsals next week I'll try this for awhile and see if that's doing it.

Just process of elimination.

Just cable & guitar?
Just guitar and pedalboard (out front) on its own
Just guitar and loop pedalboard together

This should narrow it down considerably. Once you've ascertained which 1/3rd of the rig is playing up then you can dig deeper into that part.

I bet it's a cable. It's almost always a fucking cable.

Well said, Johnny

[fuzzjunkie]

How deep into a set are you when this happens? Could something be overheating, like the power supply? I used to have an issue with my vintage Big Muff, where the volume coming out would temporarily drop. I ended up touching up a few solder joints to fix it.

Is it completely random? There isn’t a consistent combination of pedals being used? Are any daisy chained to the power supply? When you test one there might not be any issues because it requires both for it to show up.

Speaking of completely random, I had another similar experience years ago that would randomly show up during rehearsals. The same thing happened. Occasionally the volume between the guitar and amplifier would seemingly drop.

After several weeks of this and numerous equipment tests, I finally realized that it would happen when the other guitar player would step on my cable. I had tested the cable a few times and it worked fine. Some crystal-chakra type would say that our energy was misaligned or something, but it did seem like his polarity or something was the opposite of mine.

The bass player or myself could stand on my cable without any change in the signal between my guitar and amplifier, yet it would drop significantly in volume if he did. The fix was to simply keep him on the other side of the room/stage.

[øøøøøøø]

Intermittent problems are so tricky.

Agreed that starting with guitar + one cable + amp is best practice. Since your issue seems progressive and intermittent, my course would be something like this:

• Set up a mic, tape down a key on a synth, plug it straight into the amp and record/walk away. Let it go for an hour or two, then go back and look at the waveform in the DAW. Does the level visibly change? If so, you know the issue is with the amp (most likely a tube).
• If that doesn't reveal a fault, jumper the effects loop with one good cable. This should ensure that any switching jacks, etc are activated to enable any associated effects loop circuitry. Repeat the "record, walk way, evaluate" procedure
• If neither of those steps revealed a fault, we still haven't ruled out anything (that's the frustrating nature of chasing intermittent faults), but we've at least done some due diligence and can proceed to the pedalboard rig. Using a different amp (if possible), plug only the front-end pedals in and repeat the "mic up, record, walk away, examine recorded level" procedure.
• If no fault, repeat with ONLY the effects loop section (you can plug it into the front end of the second test amp)
• If still no fault, set up the entire rig as you use it and repeat the test procedure for a long-ass time (overnight)?
• If no fault reveals itself there, repeat all tests and try applying environmental stresses to suspect components in hopes of triggering a fault (mechanical stress/wiggling/tapping, etc)

Good luck and I don't envy you