Re: Effects Loop Switches

[rnolan]

Hey Dante, no worries, if you look at the schematic (attached), I went for the cabsim output schematic where I knew there would be a switch, lower right hand side, you can see the switch to select MIC/LINE, that's where I worked it out.  And yes definitely non shorting.  Upside of you pulling it apart and knowing how the internals work, to spray contact cleaner, focus on either side, not top and bottom as the bit you need to clean is where those spring loaded side contacts are.

At a pinch you could use a guitar 2 way PU coil splitter toggle switch (the ones with 6 pins DPDT (double pole double throw) e.g. DPDT) as they do the same thing and wire it to the PCB (six wires) and they would probably mount to the chassis hole (side ways, not vertical ). Note of caution though, you'd want to make sure nothing gets grounded to the chassis if you did try this idea.

@Harley, you are right, steel wool (while being nice and fine) leaves lots of crap around.  I've used it to polish frets before but you need to cover the PUs.  I just ordered a set of fret polishing erasers (Fret erasers), the 8000 one would probably work ok to polish contacts (or use 8000 wet/dry paper).

[Dante]

Whelp, I ordered the wrong switches again. Thing is, the ones I got looked NOTHING like the sample and didn't match the size in the Spec Sheet online, so the pins were way too tiny again.

I am tired of waiting, I put the old switches back in. The one for FX Loop A is acting weird. It seems to not affect Channel A when I set it for Inst or Line. It's on Line level, regardless. It's difficult, but I can get it to Inst level with a 'half-push' in. Those front contacts are not behaving correctly when the button is out I guess....I'll look at my solder there, but I tested all the pins after install, using my multimeter. Everything was behaving as it should.

Here's the weird part: When I set the LoopA to Inst level, ChB gets louder. Like it's on Inst level. ChA stays at line level. So, the switch is working (I guess) and there is an issue in FX loop A perhaps. I'll do some more troubleshooting.

For now, I can jam with it on Line level and both loops are working fine (ping pong delays are doing the ping pong thing).

[rnolan]

Hey Dante, well that's a real bummer . So I attached the schematic, if you look top RH corner (and zoom in allot) you can see the 2 switches in the circuit.  But why would the A ins/line switch affect B .  Have a close look at the traces in case the soldering has caused any issues (maybe check the signal paths/traces around the switch mounts).

Of interest, you can see on the schematic how a plug into the return breaks the straight through connection (shorting jack).  So there is always dry signal on the send.  Also seems a couple of components have been "whited out" (just to the left of EFFECT_A and EFFECT_B)

For now, I can jam with it on Line level and both loops are working fine (ping pong delays are doing the ping pong thing).

[Dante]

Another day, another weird situation. I took the MP-2 apart again and looked over my soldering job on the switches. I was being extra cautious and just melting the solder and pulling away. I suspected I needed to add a bit more to each little connection - to be sure.

For a moment, I considered pulling the switches and wiring them both to Inst level using a couple little wires to jump the contacts.....just for a moment.....glad I didn't do that.

I tested the switches with my multimeter. They're working just fine....don't pull anything, don't add any jumpers.

Hooked it back up and here's what i got:

Loop A Line level
Loop B Line level
sounds like = line level in each loop (seems reasonable)

Loop A Inst level
Loop B Inst level
= line level in each loop again (huh?)

Loop A Line level
Loop B Inst level
= Line level in Loop A, Inst level in loop B?
Loop B is screamin loud compared to A

Loop A Inst level
Loop B Line level
= line level in each loop again (huh?)

I don't get it.

[Harley Hexxe]

Dante,

   This is beginning to sound like something in the circuit is not quite right. Maybe a resistor is drifting in its value, or possibly a cap beginning to fail. Take a look at the caps in the circuit with a magnifying glass and see if you can spot anything that looks like leakage or maybe a slight bulge at the end of it. Ceramic disc caps won't show any of these signs, but axial or radial caps might.

   I wonder if you can test each side for DC voltage. They should be pretty close to the same if you can. If there is a significant difference, then that would tell me there is something going on in one of the loops circuits.

[Dante]

Are you ready for this? The MP-1 Classic loops behave exactly the same way, I think it's correct.

I have both on Inst level in the Classic, I'll probably run the same in the MP-2. I still don't get it. Does anyone else run into both their FX loops? Can you try this out and see how yours behaves?

I'm guessing you're not supposed to set Loop A to Line and Loop B to Inst at the same time.


Never noticed this before; the pushbutton switches are backwards in the Classic. Switch In is Inst level, switch out is Line level. MP-2 is the other way around

[rnolan]

Well that's confusing.  The loops are supposed to be independent, and appear to be so in the schematic.  When I was checking the circuit diagram I couldn't see any way that they would affect each other.

You "should" be able to have one at inst lv and the other at line and individually adjust their respective mix setting.  But then, where do they go in the stereo mix    The schematic in the manual shows them being fed from either side of the stereo out from the chorus, so A goes to A and B to B.  Moreover, A return goes out A and B return to out B.  So that they interact makes sense from that perspective as it affects the overall output.

I'm currently using the MP-2 loop in my live rack but it's set to line with the Midiverb4 in stereo in the loop and mix levels set to 25% on both.  I use 25% because that's what a default blank preset has and adjust the MV4 accordingly.  Except for the big echo I need for She Sell Sanctuary, it's up around 60% IIRC.

[Harley Hexxe]

That is confusing. We're obviously missing a piece of the picture here.

When the stereo loops were put in these preamps, I believe it was because more of the effects processors available were already stereo units, and many of these also have instrument/line level settings in them too. So, this poses the question; are we using the preamp inst/line settings correctly?

   Personally speaking, I'll use the line setting on the preamp to reduce the noise floor from the preamp, especially on higher gain settings, going into the effects, but this is really for recording purposes. To be honest, I don't really like putting too much into the preamp effects loops. Maybe some additional modulation and delay effects, but that's about it. I put my outboard reverb in between the preamp and power amp, and that always the last effect before the power amp.

   When I'm using the Eventide, then the effects chain becomes a bit more complicated. That needs to be before any other effects I might be using. That is how my rack grew into the large one that I have. I don't use the effects loops at all with that. Everything is between the preamp and power amp. That is where I have multiple outboard effects after the harmonizer.

[Dante]

I agree - there's something we don't understand here.

The bottom line is; my switches are working. That was the rabbit hole I went down. I'm not sure why they work the way they do, but my multimeter says they're working. I need to just accept that and be on my way.

Sorry I never came up with a replacement switch for anybody else, but I can walk you through getting them apart and cleaning them up

[rnolan]

Hey Dante, do they have to come off the PCB to get pulled apart and cleaned (I'm assuming yes?).

I currently use the MV4 in the loop and it's of course stereo and line level.  It's working ok.  I do prefer using a  desk and fx send but this way is compact.

[Dante]

Yeah, the tops of the pins keep the top cover of the switch on....gotta desolder to get them apart....sorry

[rnolan]

Hey Dante, well that's just how it goes... worth asking the question though.

Fortuitously all mine are working ok (not that they ever get used much).  I do switch between 2 x 12 and 4x 12 cab settings sometimes when recording.  Initially I liked the 2 x 12, now I seem to prefer the 4 x 12 setting. Very different sounds (as you'd expect).

I have had to clean the switches in the studio rack MP-2(s), but they came good with a blast of isopropyl alcohol spray and a few toggles.  But it also turned out that I was loosing a channel intermittently because the mixer assignment switches (that select main, subs 1&2, 3&4) on some channels have gummed up. I tried cleaning them (from the outside) to little affect. So I retired that desk for now and put in another.  Chasing that down was quite frustrating, is it a lead? is it a MP-2 out issue? mostly turned out to be mixer switches.  So now I cover my mixers with a soft cloth blanket when I'm not using them to keep the dust out.  To be fair, the mixer in question I've had for 30 years.