Stumped by volume drop in amp/pedal board set up

Can you try weeding out one pedal at a time to see if a pedal is the culprit ? Or putting a voltage tester on the power supply to monitor it.

With an intermittent problem like this, it's probably something simple in the signal chain--like a cable. It could be a long cable from your guitar to the pedalboard, or the pedalboard to the amp. It may be one of the short pedal interconnect cables.

I mention this because over the last 45 years of my rock and roll career (har!) I have personally experienced this several times. The cause in all cases was "noise free" instrument cables. These are made like a normal coaxial instrument cable, but have an extra layer of conductive cloth--or more commonly on current-production cables--a carbon-impregnated polyethylene sleeve over the inner core conductor's insulator. Look:



That conductive sleeve is designed to reduce movement of the braided shield conductor against the inner insulator; it cuts down on handling noise, etc., as the cable is moved around.

Things go pear shaped when the cable assembler solders the terminal plugs on the cable and fails to trim back that super-thin sleeve by about 1/4".  In many cases, the conductive sleeve is the same color (usually black) as the core conductor's insulator, which basically renders it invisible.  If the sleeve makes contact with the core's solder joint, you get a partial volume drop, and the guitar will usually also sound really dark, with the tone control on the guitar having little or no effect on the tone.

That's a pretty interesting and unique power setup there. 18v power lithium batteries for the amp. I like it !

Should be great to drill and cut into the music that way.

Intermittent electrical gremlins can happen anytime, and if I were a pro, I'd have 2 complete sets of cables ready and waiting to swap in when it happens.

Then you can test the bad set at your convenience, and in simpler setups. And if that doesn't work and your back up, backup up set doesn't work, you're either cursed or it's a device issue like dirty input sockets. You didn't mention checking and cleaning input sockets.

Try that and you might sleep better at night.

And of course, ANY cable that gets moved around a lot...has the best chance of degrading. No doubt you've already swapped guitar cables so it's probably something else. Did you check your guitar jack ? They wear out and get dirty too. No doubt you've tried another guitar already.

But I'm intrigued by your "regulation" chips.

[super simple - the 18 volt battery is connected to an on/off switch and the leads from that feed (4) 7809 9vdc regulator IC's which are connected in parallel to spread the load to the power jacks in the enclosure.]

Let's break that down.

super simple...hmm.

the 18 volt battery is connected to an on/off switch...ok

and the leads from that feed (4) 7809 9vdc regulator IC's...um...4?

which are connected in parallel...one 18v source is regulated by two 9v regulators in series TWICE ? yep. lost me there. Maybe two 9v lines ?

to spread the load to the power jacks in the enclosure...I would expect only one 18v input on the amp, so why "jacks" ? Are there two 9v inputs ?

I'm just curious about this setup because my experience with battery powering car amps and small class D amps, it is more about CURRENT than voltage, and volume is very much affected by insufficient voltage and current(For example, 9v at 4amps seems about the same as 12v at 2amps sometimes).

And your 18v battery might start at 20v when first charged, and drop to the floor when discharged...as you well know...hence the regulating chips.

But what do the regulating chips do when they no longer have enough voltage and current to regulate ?

Mine shut themselves down.

Suppose one of your chips is bad and shuts down prematurely ?

You'd suddenly have a voltage and current drop.

This isn't very likely but I've seen chips misbehave intermittently due to static electricity and temperature and their horoscope for the day.

But this is only one part of your set up, an 18v battery dedicated to the amp...except it's not. The 18v is apparently also being used to power the 9v pedals and it's also regulated at 9v...or 18v ?

I mean if there are two 9v regulator chips to produce regulated 18v to the amp on one wire, is the remaining two 9v regulating chips sending out 9v on TWO wires that power pedals ?

In short, my operating assumption is that there are 3 power circuits, with 2 different voltages, and the same polarity.

Ok then, the pedals don't draw near as much power as the amp will at volume, and they aren't on all the time.

But the amp draws a LOT of power...especially on lower notes.

You might notice the lights dim on your pedals if your power is getting low, and maybe, the battery sag in Voltage could trigger a shutoff in a regulating chip.

But that wouldn't be intermittent, just curious. I'd dedicate the 18v to the amp myself but that's me. And there is some power loss from the regulating chips as well. Power loss bad. I'd also have to test the amp and see if regulated power is really useful. The chip might turn itself off without warning but running power directly into the amp will give a better clue that the battery is exhausted when the volume reduces. And then you swap in a backup battery in a simpler system. Right ?

Yours is a cool solution though.

I use the old version 9v boxkings and 12v/9v Talent batteries. Both have regulated 9v and MOST importantly, status lights ! I love those status lights.
I think Talent has an 18v version but I bet it's not regulated sadly. I'm thinking of a Quilter rig and wasn't really sure how I want to power it. I have the cabling to create 18v from two 9v battery packs I think, so that's my working plan at the moment. But your idea of using an 18v tool battery is interesting too.

So what happens to a Quilter if it sees 24v ? Turn into a 100watt monster or does it shut down ? My experiements with cheaper stuff suggest DC powered amps just take what Current it needs and doesn't care much about voltage. But what do I know ? A car amp isn't a Quilter !

And after all that, my bet is on dirty/faulty device inputs and cables. Been there, done that !

Peegoo, I took my DMM and connected it to the cable that connects my guitar to the board. That checked out fine - infinite ohms while moving the cable around. I left the DMM connected to that cable end and then powered up the board and with all of the pedals connected, receiving power, but all in bypass mode the DMM read 4.68Mohms. I then pressed up and down on each of the cables to see if the reading changed and on a couple of cables the DMM briefly flashed to 4.69 or 4.70Mohms and then returned to 4.68. Is this an effective way to test the cables and if so does this data tell you anything about the state of the cables? I'm hoping to avoid having to take everything apart as there are about 40 cables, organized and secured with zip ties, etc, but please don't hesitate to say "Pete, you lazy slug. You need to disconnect them and check them individually."  Thank you!!

That’s exactly how I T/S complex systems when I was in the AF.

There may be too many bits of equipment, too much gain, sharing the same 0V common. Impedances in their returns could lead to positive feedback between them and the whole system becomes unstable.
I suggest to run each block of equipment, ie pre fx, amp, loop fx on separate power that are isolated from each other, part from the signal connections.
Sorry if that’s how you’ve done it, if so I missed it.

If you suspect a cable issue, buy a cable tester. I bought one a few gears when MF had one as their “Deal of the Day”. I love it. I can test just about any kind of cable there is by simply plugging it in.

Interesting thread !

A cable with capacitance so high it makes tone pots useless ? Ooooh, ouch.

A way to test cables with a ohms tester ? Cool !

Yep, I thought 4 regulators should be 3.

And another vote for isolated power, especially between 1)different device types and even 2)different manufacturers and sometimes 3)different DECADES.
I once tried to cut down on battery weight by breaking all 3 rules and not only did I get noise, but I could actually use a knob on one device to change values on a different device ! Spooky. And for sure, some devices just don't work well with others.

DrKev : sorry about the long Covid. I've had "long epstein-barr" since I was 19 and am always cycling up and down. One gets used to it and compensates over time. Hopefully "long Covid" is a lot less permanent ! I think a lot more eyes are on the problem due to it's rumored large scale. I'm hoping any help found will help EB sufferers as well. We'll see. As for cables, many have bagged their solderless patch cables. But maybe there's a way to turn YOURS into a solid soldered solution to keep the custom lengths ?(and your investment). And yeah, stop stubbing your toe. I broke my right little toe stubbing a heavy old Epiphone case last year. I don't recommend this ! Thought I'd let you know there's no upside to it.

Thanks Stinger, I have not tried a different power source yet, but that is my next step.  I don't hear any other popping noises - there is just a volume drop and that eventually comes back.   

I have ordered a different power supply that I plan to power with my Ryobi batteries. It is not truly isolated, but I'm hoping that it will provide the stability that I need. I have rewired my board to get rid of the daisy chaining that I had , so that now no more than 2 to 3 pedals share an output, and I grouped the pedals that are sharing an output so that ones that are paired, are rarely/never on together. 

Hopefully this will be a nice stable improvement.

Here is the unit:New power supply