Don´t you have a scope?
To distinguish between bursts of oscillation, protection chopping audio, DC jumps, whatever.
Ear alone is not enough.

Maybe.
To make certain, get a TPA3118 board and use it the same way you are using 8932 now.
No need to order from China and wait, just get one at Mercadolivre, even if slightly more expensive.
What city are you in?
If in SP, Multicomercial and shops in Sta Ifigênia have anything you need.

Just an insanity check: remember speaker leads must *both* be floating, no speaker terminal can touch ground.
If you use a speaker jack in a metallic chassis or cabinet (many put those amps inside a Hammond type pedal box) then you NEED a plastic jack (Cliff/Marshall/Vox type), not a metallic one (old Fender type).
Measure DC to ground, no signal, at each speaker out lead, both (+ and -) must measure 1/2 +V

Recheck: with amp OFF, measure DCR to ground at each speaker terminal, when connected to amp.

No. Period.


Please post a YT video showing us what you call noise, we have no clue what that word means.

Just to see where the chips fall, I would test once more the chipamp, driving it straight from generator or at most a 1 Op Amp low gain stage, say 3X to 10X tops if beyond what the generator can supply, and from a simple power supply, not boosted batteries or regulated supplies but transformer - diodes - caps. 
Nominal 12VAC will give you some 15-16V DC

The point being to confirm the amp itself fails and not Preamp or supply throw the towel.

Did you scope the +V rail to see if it drops?

That click click click may come from amp protection but also from supply protecting itself.

*In theory* TDA8932 should work fine for that load and supply ..... in practice, who knows?

But if so, stop using it, period.
TPA3118 has a reasonably proven record so far.

As with everything, practice makes perfect.

On na boring Sunday afternoon you can spend some time reading *all* those resistors and then confirming (or not    ) with a meter.

Even better, get a plastic box with 10 or 12 divisions, and group them by value, say 1-10 ohm, 10 to 100 and so on.
Not "one division per value" but next time you need one, you check the matching sub division and you know at least you are in the ballpark.

Also: at a glance you know you do NOT have certain value, instead of each time wasting 30 minute going through all of them again and again.

Quote from: smackoj on July 15, 2025, 04:35:58 PMHi friends; A very long time away so apologies. I did a quick cleanup on this Randall RG75D model SS amp. Built in China with one 12" spkr. This amp is almost silent at idle but start playing thru it and it sounds poor with some kind of high freq noise on every note. I checked the speaker wires and there is .25 vdc on them at idle. Is that enough dc to cause a problem? thanks amigos

Not by itself.

Disconnect those speaker spade terminals and try the amp with another speaker or cabinet.

Also connect another amp to the internal speaker.

So we know whether it´s an amp or speaker problem.

Post closeup pictures showing board (both sides) and wires, we might guess what goes where.

That.

Enzo used to strip knobs, fuse holder caps, maybe a handle or corner protector, a speaker, which might prove useful later.

Sometimes even a Power transformer.

Quote from: anderson4584 on July 10, 2025, 10:56:55 AMI can always change to channel 3. But I have issues getting it back to channels 1/2. I opened up the footswitch and everything seems fine in there. I played with the wires a little bit to see if it would change anything and the only thing that changed anything is.......it typically works fine when I hold the footswitch upside down.

That makes no sense.
Do you hold pedal in your hand or put in on the floor? (so floor can push both buttons at the same time)

 

QuoteWhen this issue happens, I also typically lose a lot of power output while playing, but ONLY in the bridge pickup. If I switch to the neck pickup, I get power back. That makes even less sense..

-

QuoteTried using another 2 switch footswitch I have that goes to a Peavey classic 20MH (this works... but it ends up having the same issue, which leads me to believe it's the amp).
-Swapped some cables around, and tried different guitars.

For testing, plug a spare TRS/"stereo" plug in theb Fsw jack.
Cover open, pins visible.

Solder a short (1" to 2") piece of wire to plug ground terminal.

Then touch either of free pins (to simulate temporary switch) with the free end ... what happens?

Repeat test but now soldering wire end to a pin or another to simulate a latching switch.

This way you are testing using a bare minimum "pedal equivalent" device, very simple and easy to understand, which depends on nothing else.

Post results.

Any ideas?

Just the button or the full switch?
Post a switch picture.

CE distribution in Arizona usually has all parts Fender, even some not available from Factory any more

https://www.cedist.com/

What is the problem you are trying to solve?                                                                                                       

Quote from: dmeek on July 07, 2025, 10:48:25 PMHere is the preamp schematic. The Tone switch is a gyrator notch filter. I can't see the value of the silver capacitor on the tone board but if
I assume it is 1000PF the frequencies are: 1 - Flat, 2 - 230Hz, 3 - 1kHz, 4 - 3.4kHz. If you can read the value, let me know.
I couldn't draw the reverb section because the foil side is hidden by the footswitch jack. If you can move it and post a photo I can do it.
If you want to lift the power board and post a photo of the foil side I can do that too.

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Thanks Dmeek, incredible job, as usual.

What I find *weird* is that the exact same amp (differences are just "modernization" but design/ideas are the same) was made "on both sides of "the Curtain/Wall"" because Regent maker was an East German/DDR State run Factory.
So much so that components used are "Soviet Block" type.
Transistors are Tesla, made in Czekoslovakia, guess other components too.

Not sure where did "the Reds" get Reverb tanks, for example.

Also curious about what speakers were fit in those amps.

My point is that *maybe* East Germans copied a British amp (although an earlier discrete transistor version), the opposite sounds unlikely.
But the Londoner uses American transistors (RCA) and ICs (Texas Instruments) but Britiish Cliff jacks and capacitors.
No brand visible but those large Blue ones look same (or very similar) to those used by Marshall.

Mysteries of International trade.

Sounds like state of the art troubleshooting to me 

Quote from: blackcorvo on July 02, 2025, 03:47:59 AM

Quote from: Loudthud on July 01, 2025, 09:31:23 PMWell first thing you gotta know is what power supplies are available to run the preamp ?

Initially, I'm thinking just 12v, both for the power amp and preamp, as I already have a 12v PSU that works well with the amp, and I could easily add a 3x 18650 battery holder to it in the future.
I also have some XL6009 boost converters, so I could use one for higher voltages on the preamp if needed.
The TDA8932B board I have can work with up to 30v, but I'd probably limit it to 20v max just for the sake of not going over the speaker's max 30w rating.

Marshall Lead 12 is a KILLER little SS amp.
You can build just the preamp to drive your power amp.

Full schematic

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Preamp only:

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2 "problems" to solve:

1) you will have to draw your own PCB
There are a couple ones on the Net, also Veroboard versions, but I do not trust them.
Also designers get "creative" and add unnecessary features as diode clipping, switchable gain stages, different EQ, etc. which actually degrade it.
Best is original one which is also the simplest.

2) it needs symmetrical supplies.
Originally +/-16V but works fine with +/-12V
You already have +12V and it is easy to get -12V out of it, using a charge pump IC.
I´ve done that many times for my 12V Lead Acid battery powered "Callejero" (Street Musician) busking amps.
Didn´t even use a charge pump IC (not available way back then in Argentina) but a humble 555 oscillator, go figure.

3) Plan B: most any Distortion pedal can work as a preamp for your Chipamp, even a humble MXR Distortion + , a Tube Screamer, etc. and all those work straight from single +9V supplies, and are happy with +12V.
Or you can pad +12V down to +9V by using an LM7809.

To broaden the scope: there are a few "Amp in a Box" pedals, sporting full tone controls, search the usual "PCB Pedal" sites.
But read all comments and build only those which are "checked".
Marshall Guv´nor is a Marshall preamp channel in a pedal format, works out of single +9V and there is a tested iron-on PCB layout available. search for it.

Don´t you have a pedalboard? Or a Zoom (or similar) pedal?

Those can straight drive your chipamp.

What a complex power supply 

It scratches my minimalist brain quite the wrong way.

Oh well.