Yes these are the fitercaps of the power supply.

Hey Richard,

In theory, with other amplifiers, the effects loop is supposed to be between the preamp and the power amp sections of the amplifier head. Very few amplifiers on the market had built-in chorus effects with their effects loops, and I don't know the signal path routing in those amplifiers, but for the most part, they were and mostly are simple amplifiers without built-in effects. These only offer a single channel power amplifier stage, so you had to add another power amp for stereo effects.

To simplify this explanation in an amplifier like this, I'll use an example of a pedal board I built a few years ago using the NUX Cerberus. This integrated pedal has four effects sections, OD > Distortion > Modulation > Delay/Reverb. Now you can use this in the front of an amplifier and all of the effects are in series. Or, you can use this in 4CM because there is a Send and Return jack which is located between the Distortion and Modulation in the pedal's signal path. In this case, you are putting the OD > Distortion in the front of the preamp of the amplifier. You would then take the Send from the amplifier's effects loop and plug that back into the pedal. This sends the signal path through the Modulation > Delay/Reverb sections of the pedal. At this point the pedal has two outputs, but they are not stereo. One is a direct signal with the pedal's effects, and the other one has cab emulation if you want to turn that on in the pedal. You would take one of these outputs and plug this into the amplifier's Return jack, which would place the Modulation > Delay/Reverb after the preamp section (theoretically), of the amplifier. That would be the 4CM for a mono amplifier set up.

It's kind of odd that this pedal works this way because you have three selections to choose from when using chorus and they are labeled: CE, SC, and ST. I interpreted the last one as stereo chorus, but I don't seem to get that from it. Maybe I need to use a TRS plug from that output to get that? I'll have to send an email to NUX and ask about that.

So, to sum it up, any setup where you split effects between the preamp and power amp of an amplifier head can be called 4CM.

Hey Dante, I first bumped into the 4CM term back in the early days of the depot.  It (then) referred to connecting a stereo rack FX in between a MP-1 and stereo power amp (e.g. B200s) which I though of and referred to as chaining. So you take MP-1 A and B outs to FX L/R in and FX L/R out to power amp A/B in.  Thus 4 cables and FX in stereo after the preamp, and use the FX mix setting to control how much direct vs FX you want.  This made sense as the MP-1 loop is mono and serial and before the chorus (where MP-1 goes pseudo stereo).  Of course with MP-2 it has 2 parallel loops and programmable mix setting and is very similar to the 4CM idea as the loop is after the chorus and uses 4 cables, however the loop returns are before the cab sim.  So the way you are using it is, to some extent, an evolution of the idea and also you have a bunch of loops which allows some interesting patching options.  What 4CM means on other forums I have no idea as I don't read them.  I spose strictly speaking, any set up with 4 cables could be referred to as a 4CM?

Thanks MJMP,

   I'll be ordering those on Monday. I'll probably order several of them to have them on hand for the next MT-100 if this goes well.

    Are these filter caps? If they are then I don't need to be concerned with the tone.

Quote from: Harley Hexxe on May 31, 2024, 02:06:56 PM

Quote from: MarshallJMP on May 31, 2024, 01:17:36 PMDid that to Dante's MT100, but it's hard to find those 4700µF/80V caps in an axial housing. Good thing ADA also have the holes to put in a snapin cap (even 2 in parallel). I got these from mouser, if you want I can get you the part number. Found a 4700µF/80V snapin that fits so no need to put in 2 2200µF caps  like it was intended.

Yes please, if you would get me the part numbers, I'll order them.

I am understandably nervous since I've never done this before, but I think I have all the right tools for it and they aren't going to fix themselves.

Mouser 598-SLPX472M080H3P3

Quote from: Dante on June 01, 2024, 10:26:09 AM

Quote from: Harley Hexxe on May 31, 2024, 02:06:56 PMI am understandably nervous since I've never done this before, but I think I have all the right tools for it and they aren't going to fix themselves.

Dood, if I can do it....

That's the power transistors. MJMP did your caps, I'm going to be doing it all.

What I'm nervous about is screwing up traces on the PCB. Just like the caps, the PCB is old too.

Quote from: Harley Hexxe on May 31, 2024, 02:06:56 PMI am understandably nervous since I've never done this before, but I think I have all the right tools for it and they aren't going to fix themselves.

Dood, if I can do it....

Thanks man, I updated my diagram with actual pix of my MP-2 rig. Also added a 4CM post with a diagram for reference.

You will hear a lot of folks on here and other forums talking about the 4 Cable Method. What is is it? Why should you use it?

Okay, maybe this isn't a great 'explanation' but, you're basically running your preamp and effects units in each other's FX loops. Having the preamp in the loop allows you to use it as an effect or like a stompbox in the chain rather than just plugging into the input (resulting in the preamp distorting your effects).

Why use it? Because you have the flexibility of putting effects in front of your preamp or in the loop. Compressors, Wahs, Dirt Boxes, all sound better in front of the preamp. Whereas, Modulations, Reverbs and Delays sound better in the Loop or after the preamp (this is kinda the accepted norm, but do what you want, you will anyway).

It involves using 4 cables (duh)

Here's how to set it up:
Guitar > Multi-FX INPUT
Multi-FX OUTPUT > Preamp FX RETURN
Multi-FX RETURN > Preamp FX SEND
Multi-FX SEND > Preamp INPUT

Note: If you don't have an FX loop in your pedal chain, just run your 'after' FX thru the preamp's FX loop and the other FX in front of the signal chain, before your preamp.

PLEASE FEEL FREE TO CORRECT MY INFO, I'll update this post when I fix things ;)

Rock on! 

Dante,

I could tell a couple were photos of your rig(s). I wasn't too sure about the others though.

Still, really nice work man