3 channel Triple Rectifier Loop Mod.(Parallel to Series)

sflight said:

I recommend selling your effects and get ones that will work with the parallel effects loop. (Analog)..

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Thanks for the comment tho that means completely changing my sound as a lot of the sounds I have come from a 100% wet mix. I'm pretty set on making the loop series but just want to confirm it'll do what I want - ie. no dry sound coming through. and see what knobs/controls are disabled from it. Thanks

Let us know how it turns out. Good Luck!!

I've been experimenting with my GT-10 and the stock (parallel) effects loop in my Dual Rec. I'm pleased so far. Here's how I'm approaching it...

My best guess is that it can kill tone due to the latency of any digital effects coming into play; so that if you have any "dry guitar" signal being returned to the Mesa from your effects unit (e.g., a preamp emulation), it's causing comb filtering (funky EQ curve) when its latent (processing-delayed) signal mixes with the dry Mesa guitar signal. Maybe you guys have already determined this. I didn't see it anywhere... so there's my theory.

My first thought was to delay the internal Mesa signal (after the the mult where the send splits off) by the same amount as your processor's latency, so that the return signal would be in phase with the internal Mesa signal at the mix point. But that would require a mod to the head. Well, that's what I'm trying to avoid.

Anyway, my second thought was... it stands to reason that so long as you keep any such direct guitar signals -- that is, one latent, one not -- from mixing, you shouldn't have to worry about this tone-draining cancellation (comb filtering). This, of course, is the approach recommended by Mesa when they say to set your effects to 100% wet (no dry, latent guitar sneaking through) when using the effects loop.

Using the four-cable method, my thought was to use reverbs and delays set to 100% wet like that, letting the Mesa return do the wet/dry mixing, but then if I wanted to use a patch that had "direct" guitar in it (like a preamp emulation), I would simply be sure to avoid mixing in any mesa dry signal (in this case I probably wouldn't want the Mesa preamp sound anyway), using only the latent signal feeding the return to the head. This is accomplished by being sure that any such patch I create has the processor's SEND/RETURN turned off. So, the signal goes into my GT-10 from the guitar, then out of the GT-10's output jack to the Mesa return, which is mixed with the "muted" internal Mesa dry signal, and so causes no cancellation of the returned signal.

You could alternatively defeat the Mesa's FX loop, such that anything you pump into the head's input would make it all the way to the speaker cab with no latent return signal mixed in. You'd likely want to be switched to the clean channel, of course, if you're using some modeled preamp distortion from your processor.

Or not.

Anyway, I used it at a gig this weekend, and it sounded pretty dang good. So long as there's no latent direct signal getting mixed back into the original, the Dual Rectifier sound rings big and clear. I'm pretty hopeful I won't need to do the serial mod.

Why would you need to go to all this trouble? The *only* cause of the issue with phase and latency is the link from the Send level pot to the Mix pot allowing a small amount of dry signal through, so if you simply break this connection it's fixed. That leaves all the other functions of the loop working as normal.

(I don't have a Triple Rec by the way, I got directed to this thread from elsewhere, but I've done this mod to several Mesas and I can guarantee that it works perfectly.)

It's also not digital pedals that are the problem, it's only digital pedals that digitize the *whole* signal, instead of just the effect part. Many digital pedals leave the dry part analog even when the effect is on, including most Boss digitals. And some *analog* pedals do it as well, if the effect output is inverse phase - so going all-analog isn't foolproof.

This is such a well known problem - and it's only going to get worse, as more pedals are fully digital - that Mesa really should have fixed it years ago. It's extremely simple, they either need to fit a switch to take out the dry signal or a proper mix pot that goes to truly 100% wet, and then it wouldn't matter.

94Tremoverb said:

Why would you need to go to all this trouble? The *only* cause of the issue with phase and latency is the link from the Send level pot to the Mix pot allowing a small amount of dry signal through, so if you simply break this connection it's fixed. That leaves all the other functions of the loop working as normal.

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I'm trying this route because making the mode seems like more trouble to me.

But to be clear: are you saying that simply cutting a wire from the send pot to the mix pot is all that is needed to fix this? I thought it was more involved. Hell, if that's all there is to it, I'd happily do that.

I've also heard that after the mode, there's still some bleed. Sounds like your experience is different. The tech I talked to said there's so much RF and other types of crosstalk flying around in these high-gain circuits that there's a lot of 'voodoo'.

(I don't have a Triple Rec by the way, I got directed to this thread from elsewhere, but I've done this mod to several Mesas and I can guarantee that it works perfectly.)

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Cool. I have a dual rec, actually. I'll bear your admonition in mind for possible future action.

However, I'm not crazy about losing some of the functionality. What goes away, exactly? The solo control? The master volume? Loop assignability and footswitching? Mix pot function? All of the above?

It's also not digital pedals that are the problem, it's only digital pedals that digitize the *whole* signal, instead of just the effect part. Many digital pedals leave the dry part analog even when the effect is on, including most Boss digitals. And some *analog* pedals do it as well, if the effect output is inverse phase - so going all-analog isn't foolproof.

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Interesting. I'll have to check the schematic of my GT-10, but I have the impression that everything's digitized right up front.

This is such a well known problem - and it's only going to get worse, as more pedals are fully digital - that Mesa really should have fixed it years ago. It's extremely simple, they either need to fit a switch to take out the dry signal or a proper mix pot that goes to truly 100% wet, and then it wouldn't matter.

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I have to agree. One end of the pot sweep says "100%", which leads one to think it means 100% wet, which is not the case. Seems very misleading.

Yes, all you have to do is disconnect the 'dry' end of the Mix pot. If you want to be really thorough you can move the center connection of the Mix pot to the 'wet' end as well, which will make the pot completely inoperative - with just the dry end disconnected, it will still have some effect on the return level - or you can just leave it turned all the way to wet.

On some amps - just the ones with selectable loops, I think - you will need a patch cable in the FX loop if you want the loop operative with nothing in it, but on others you don't.

I'm not sure if there's any bleed or not - I don't hear any, and certainly it fixed the problem with tone suck caused by my Line6 DL4 (well, apart from the normal Line6 tone suck ). I can't see any reason there should be any.

More recent Mesas say 10% and 90% on the mix controls, which at least is honest, but it's such a basic design mistake and so easy to fix you would think they would have done something about it by now. It's an extremely common complaint (rightly so) and many other companies have loops which don't cause this problem.

And I'm also sure the GT-10 will be all-digital, if it has any COSM effects in it - maybe unless you can turn all these off, but probably even then.

Sounds great. But, isn't there some loss of feature functionality with the FX switching and the solo and master controls?

Also, the PDF I got from Mesa for the mod shows some resistors that come into play. Do you ignore those?

No, the only change is that there is no longer that residual 10% of dry signal in the FX loop, which is what causes all the trouble with phase and latency. On the amps with selectable loops and the Solo feature associated with that, you will need to put a short patch cable into the loop if you want to run the loop but aren't actually using effects in it, that's all. On the amps with non-selectable loops you don't have to do that. (Or you could change the Send jack to a switched one, like the amps with non-selectable loops, and have the link automatic when nothing is in the jacks.)

I really don't know why Mesa want to make this more complicated than it needs to be. I truly wonder whether there's anyone at Mesa that really understands this problem. When I owned a Formula preamp, there was a line in the manual that said something like "we find that most players prefer to run their effects units in line after the preamp instead of in the effects loop we provided, because it sounds better, and we agree" - which of course it does, for exactly the reason we all seem to know now! So why haven't they fixed it?

I see. So after making this mod, the internal preamp dry signal is gone altogether, regardless of the mix pot position, which only impacts the return signal level. The only preamp signal that can get to the power amp is through the send/return loop. Solo level and switching via footswitch as well as the master control are all unaffected. FX loop switching via footswitch is also unaffected?

Do I have all this right?

Yes .

Thanks for helping me along. :lol:

But I guess since the FX loop is made to be "full time wet", that does mean the footswitch for the loop changes a bit, right? It would become a kind of mute switch for the amp, wouldn't it? Either the loop is on (full wet, no dry) or it's off (no wet, no dry). Is that right?

Or does the loop footswitch actually switch a separate dedicated direct preamp feed in instead of the loop/mix circuit? That would make sense, since there is a volume loss when engaging the loop via the footswitch. Or would it? :?:

The footswitch simply activates the send/return jacks, rather than bypassing the whole loop circuit - that's why you need to bridge the loop with a patch cable, on the amps with a selectable loop, if you want to run any of the loop functions (Solo etc) with no effects in the loop.

Or, you could copy the circuit from one of the non-selectable-loop amps (eg Single Rectifier) and use a switched jack in the Send, with the switch terminal connected to the return - that does the same thing as the patch cable, but inside the amp.

It depends on how much soldering you want to do .

Hey guys I made a post here but I'm now thinking sticking it in this thread is more appropriate.

I made the mod as per picture, though only removing 2 of the resistors. Results are -- soundwise the mod works great! FX sound like they're supposed to again, tone is a +lot+ better. The solo still works and the output still works. The only lost functionality is switching the loop on and off.
However there is a ridiculously huge volume drop as a result of the mod, not sure how much this has been touched on - think someone briefly mentioned a drop, but i wasn't expecting it to be this huge. Is this expected? The output knob has gone from a slight touch will blow your head off to having to crank it to max to make it close to rehearsal level. My plan to resolve this is get a pedal that boosts the volume for the FX loop, does this sound normal? Thanks

newm1ke said:

Hey guys I made a post here but I'm now thinking sticking it in this thread is more appropriate.

I made the mod as per picture, though only removing 2 of the resistors. Results are -- soundwise the mod works great! FX sound like they're supposed to again, tone is a +lot+ better. The solo still works and the output still works. The only lost functionality is switching the loop on and off.
However there is a ridiculously huge volume drop as a result of the mod, not sure how much this has been touched on - think someone briefly mentioned a drop, but i wasn't expecting it to be this huge. Is this expected? The output knob has gone from a slight touch will blow your head off to having to crank it to max to make it close to rehearsal level. My plan to resolve this is get a pedal that boosts the volume for the FX loop, does this sound normal? Thanks

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Thanks for the input, newm1ke. Good to hear.

Did your mod leave the mix pot functional at all? If so, could it be that you don't have it cranked all the way clockwise, and so the return level is attenuated?

94Tremoverb said:

The footswitch simply activates the send/return jacks, rather than bypassing the whole loop circuit - that's why you need to bridge the loop with a patch cable, on the amps with a selectable loop, if you want to run any of the loop functions (Solo etc) with no effects in the loop.

Or, you could copy the circuit from one of the non-selectable-loop amps (eg Single Rectifier) and use a switched jack in the Send, with the switch terminal connected to the return - that does the same thing as the patch cable, but inside the amp.

It depends on how much soldering you want to do .

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Cool, thanks.

Hey, if this is how it is wired, why does the dry signal drop in volume when the FX loop is engaged, currently, do you know?

Does it still drop in volume if you put just a patch cable in the loop? If not, the volume drop is caused either by the effects units themselves - possibly an issue with either the send or return impedance loading down the signal, or a phase reversal in them. If it does... I don't know! I can't see any reason from the schematic that the volume should drop otherwise.

newm1ke - I saw your other thread. If you can, put everything back exactly as it was and hopefully it will work properly again. Then just disconnect the dry end of the Mix pot. Removing the switching transistors and jumpering the boards like that is totally unnecessary, and I would guess you've just connected something wrong.

There's no logic to removing the transistors in the interests of "purity", unless you are using an all-tube effects chain, and even then it really wouldn't matter. There are at least two Mesa amps that deliberately use transistors in the signal path (carefully without telling anyone they're there) to *improve* the tone. If you really want purity, just bypass the loop altogether with the rotary switch.

Hey, 94 -- did you see the mod schematic earlier in this thread (not the photos, the schematic, which is different, I think)? Why do you think they're messing with resisters and doing all the extra jumpering stuff? You're basically saying cut a single wire, right?

That's the same mod schematic that a tech at Mesa sent me.

Yes, I saw the schematic - that's what I'm basing saying that it should make no difference to the volume on. I really don't know why they want you to do all that stuff. To be honest I haven't looked very closely at either that or the instructions earlier on to see exactly what they're trying to do, since I *know* that the only thing you need to do is remove one wire. It's worked perfectly on every one of the several Mesa amps (I forget exactly how many, more than five and less than ten but all different models) I've done this to.

Hey guys thanks for replies, just thought I'd update you on he issue I had coz I think I've resolved it. I got the MXR 10 Band EQ ped you guys are all raving about, stuck it at end of loop (well, before delay) and cranked the gain/volume levels on it and it now works great. It cranks the volume comfortably again, nowhere near as much as before the mod but I prefer it like this as the output is much more management rather than millimetres. I had a good rehearsal/gig volume at 2 o'clock on the output, and can engage solo if needed more for watever reason. Very happy with this mod.

The only remaining issue is channel switching. There's still very loud thuds when switching between channels, louder as the volume goes up. This is maybe something for another thread as I've tried the FAQ stuff of switching through channels in standby but still doing it throughout practise.

Other than that, very happy with the results

94Tremoverb said:

Why would you need to go to all this trouble? The *only* cause of the issue with phase and latency is the link from the Send level pot to the Mix pot allowing a small amount of dry signal through, so if you simply break this connection it's fixed. That leaves all the other functions of the loop working as normal.

(I don't have a Triple Rec by the way, I got directed to this thread from elsewhere, but I've done this mod to several Mesas and I can guarantee that it works perfectly.)

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Just wanted to let everyone know that this worked for me. I recently bought a Boss Re-20 space echo and a volume pedal and wanted to run them along with a chorus pedal in my FX loop. I have a mid 90's 2-channel Dual Rectifier solo head and was quite frustrated by the residual (~10%) dry signal remaining in the chain when the mix knob was at 100% wet.

So, I found this forum, found this post, opened up my head, de-soldered the green wire running from the send pot to the mix pot, and wrapped the end with some electrical tape. It was extremely simple, took maybe 10 minutes. Fired my amp back up, the loop rotary dial still works (bypass, on red & orange, red only, orange only, foot switchable), and now no dry signal is passing through my FX loop when the mix is at 100% wet. Works just like I wanted it to. I couldn't be happier. Thank You 94Tremoverb :mrgreen: