Made my loop serial, still sounds bad.

[Chiliphil1]

Hey guys, using the info found on this forum (thank you) I converted the loop on my ToV from parallel to serial in hopes that it would become useable. I don't use any effects but I want to be able to utilize the master volume. I did it by removing the green wire from the wiper and then moving the orange to the center wiper with the red. At the same time I tossed in some new (used) pre amp tubes and a set of EL-34's. Got it all back together, what a PITA! As soon as I flipped the loop, same problem. Basically it takes a lot of the aggression away and neuters the bottom end. I played with the loop level knob and it made a difference but still sounded terrible.

Has anyone successfully done anything to one of these amps to make using the loop possible? Thanks in advance.

Edit: Forgot to mention, I DID have a jumper in the loop, just a small patch cable.

 

[tele twister]

I did a parallel to series loop mod on my ROV II, but my wires are all grey. IDK if this applies to your amp.
I searched, but can't find the schematic I used. There were 3 wires on the effects level pot, 1 is disconnected and taped off,
and the other 2 are soldered to the center lug (wiper?) of the pot.
I thought the center lug was just a common place to connect the two wires, full time, essentially bypassing the pot.
AFAIK, after connecting the two wires to the center lug only, the pot does nothing anymore, and my loop works great in series...
...which leads me to guess your tubes created the tone change.

 

[elvis]

I think you may be fighting a different issue. The main reason for converting to a series loop is for use of digital FX in the loop. The parallel signal creates nasty artifacts when processing digitally delays the signal slightly.

My experience with Mesa loops that have a %Wet knob, there is very little difference, if any, between setting the knob at 100% Wet and bypassing the knob entirely. If you get parallel bleed, it's not generally the knob, it is in the circuit and/or tubes.

As for your issue, it seems that the circuit that drives or buffers the FX loop may have some filtering in it. Remember that the FX loop has additional circuitry that the internal path does not. This is a great exercise in proving that tone change when using loop processors is often not the processor, but the amp's loop circuit.

You may need to alter the loop circuit to make it more flat vs. frequency.

 

[Chiliphil1]

I think you may be fighting a different issue. The main reason for converting to a series loop is for use of digital FX in the loop. The parallel signal creates nasty artifacts when processing digitally delays the signal slightly.

My experience with Mesa loops that have a %Wet knob, there is very little difference, if any, between setting the knob at 100% Wet and bypassing the knob entirely. If you get parallel bleed, it's not generally the knob, it is in the circuit and/or tubes.

As for your issue, it seems that the circuit that drives or buffers the FX loop may have some filtering in it. Remember that the FX loop has additional circuitry that the internal path does not. This is a great exercise in proving that tone change when using loop processors is often not the processor, but the amp's loop circuit.

You may need to alter the loop circuit to make it more flat vs. frequency.

Understood. Thank you for the reply. I guess I'll just have to live with it.

 

[Don_Sloan]

I had the same issue with my Road King v1 with it losing a ton of lows and low mids with the loop engaged. Looking at the schematics, it appears the loop design is nearly identical in your amp.

There is a 2.2uf capacitor connected to pin 3 of tube V4a (which is the effects loop recovery stage). Changing this to a 10uf tantalum capacitor should eliminate the tone suck or at least reduce it substantially. Just be sure to install it in the right direction with the "+" end connected to pin 3. This worked great for me.

 

[Chiliphil1]

I had the same issue with my Road King v1 with it losing a ton of lows and low mids with the loop engaged. Looking at the schematics, it appears the loop design is nearly identical in your amp.

There is a 2.2uf capacitor connected to pin 3 of tube V4a (which is the effects loop recovery stage). Changing this to a 10uf tantalum capacitor should eliminate the tone suck or at least reduce it substantially. Just be sure to install it in the right direction with the "+" end connected to pin 3. This worked great for me.

Awesome! Thank you. I will try to get this done asap. Finally got the amp in a band setting last night and it needs that MV. Having to balance the channels over and over kinda blows.

 

[Don_Sloan]

I had the same issue with my Road King v1 with it losing a ton of lows and low mids with the loop engaged. Looking at the schematics, it appears the loop design is nearly identical in your amp.

There is a 2.2uf capacitor connected to pin 3 of tube V4a (which is the effects loop recovery stage). Changing this to a 10uf tantalum capacitor should eliminate the tone suck or at least reduce it substantially. Just be sure to install it in the right direction with the "+" end connected to pin 3. This worked great for me.

Awesome! Thank you. I will try to get this done asap. Finally got the amp in a band setting last night and it needs that MV. Having to balance the channels over and over kinda blows.

You're welcome! Hopefully, that solves your problem like it did for me. I couldn't be happy without my MV!
By the way, if you need a copy of the schematics for your Tremoverb, you can download them here: http://www.thetubestore.com/lib/thetubestore/schematics/Mesa%20Boogie/Mesa-Boogie-Tremoverb-Schematic.pdf

Thetubestore.com actually has a decent archive of amp schematics and typically better quality than ones I've found elsewhere on the internet.

 

[GJgo]

Subscribing to learn.

I tried the loop in my TOV last night for the first time actually, to run my looper pedal through it. It makes things so quiet in the loop (regardless of knob setting) that it's unusable. If I run the looper into the front it works fine.

This is bass ackwards from the loop in my mark III. If I run the looper into the front it works but has a bad sound, but if I run it in the loop it works great.

 

[Chiliphil1]

Subscribing to learn.

I tried the loop in my TOV last night for the first time actually, to run my looper pedal through it. It makes things so quiet in the loop (regardless of knob setting) that it's unusable. If I run the looper into the front it works fine.

This is bass ackwards from the loop in my mark III. If I run the looper into the front it works but has a bad sound, but if I run it in the loop it works great.

Dumb question but did you try the loop level knobs on the back? For me it helps but it still isn't as good as it is without the loop engaged.

Still planning to do the cap mod listed above. I'll post back once I do.

 

[GJgo]

After writing I did go back & actually read the loop level instructions (gasp!), and I then set the loop levels up by patching the loop direct pass through. Once I got that all dialed in (send level 1:00 and mix level 100%) it actually sounded better than with the loop bypassed, I assume because it adds another tube stage. Plus, with the master volume added I can balance the master vs. channel volume for the best fatness.

After I was happy with this I re-introduced my looper & set its volume up, and then it actually all sounded fine. I think in general I'm going to run the amp with the loop on w/ a patch cable whether I'm running a pedal in the loop or not.

 

[Chiliphil1]

After writing I did go back & actually read the loop level instructions (gasp!), and I then set the loop levels up by patching the loop direct pass through. Once I got that all dialed in (send level 1:00 and mix level 100%) it actually sounded better than with the loop bypassed, I assume because it adds another tube stage. Plus, with the master volume added I can balance the master vs. channel volume for the best fatness.

After I was happy with this I re-introduced my looper & set its volume up, and then it actually all sounded fine. I think in general I'm going to run the amp with the loop on w/ a patch cable whether I'm running a pedal in the loop or not.

Nice! Glad it worked for you. I'm still fighting with mine.

 

[afu]

I would bypass the pot altogether by tying the return jack to the return amp stage, whether that's just soldering the two wires or adding a short jumper on the board. That will at least remove the mix pot, since a serial loop would not need it.

My 3ch is this way and it's an improvement. That said, I keep my MVs as low as possible, so the Send stage is not clipping. The output control is for driving the power amp when the loop is engaged, so the channel volumes only need to be up enough to pass a decent signal. It makes a big difference for me.

Also, the output needs to be close to Noon to have a balanced sound. So set channel volumes with output at your preferred maximum level. If a little more volume is needed, the send can be bumped up a little to fatten the sound.

 

[Chiliphil1]

I have tried everything. I did patch cable, no patch cable, level max, level min, full wet, full dry, MV high channel low, channel high MV low. Nothing makes it sound the same as with the loop bypassed. It looses so much bass and cut when I have the loop on it's like a totally different amp..

I guess I am just going to have to be without a loop :roll:

I may try that bypass idea posted above. If I go that way I'll report back with the results.

 

[domct203]

Did you try changing the FX Loop driver tube?

Dom

 

[Chiliphil1]

Did you try changing the FX Loop driver tube?

Dom

Yes, I've tried Mesa stock, JJ, and Shuguang thus far. Nothing seems to make a difference.. I also don't want to give the impression that it's "bad" it's just different and seems to take that big bottom end away which really, is why I wanted a recto to begin with.

 

[DS-1]

I had the same issue with my Road King v1 with it losing a ton of lows and low mids with the loop engaged. Looking at the schematics, it appears the loop design is nearly identical in your amp.

There is a 2.2uf capacitor connected to pin 3 of tube V4a (which is the effects loop recovery stage). Changing this to a 10uf tantalum capacitor should eliminate the tone suck or at least reduce it substantially. Just be sure to install it in the right direction with the "+" end connected to pin 3. This worked great for me.

Can you please post a picture of the mod?

Thanks a lot!

 

[Don_Sloan]

I had the same issue with my Road King v1 with it losing a ton of lows and low mids with the loop engaged. Looking at the schematics, it appears the loop design is nearly identical in your amp.

There is a 2.2uf capacitor connected to pin 3 of tube V4a (which is the effects loop recovery stage). Changing this to a 10uf tantalum capacitor should eliminate the tone suck or at least reduce it substantially. Just be sure to install it in the right direction with the "+" end connected to pin 3. This worked great for me.

Can you please post a picture of the mod?

Thanks a lot!

I will look when I get home this evening and see if I took a picture of it. Of course, mine would be on a Road King I, so if you don'thave the same amp, the location of the cap might be different, but there were a few different models that had the same design mistake.

I'll see what I can find in my pics though.

 

[Don_Sloan]

I have tried everything. I did patch cable, no patch cable, level max, level min, full wet, full dry, MV high channel low, channel high MV low. Nothing makes it sound the same as with the loop bypassed. It looses so much bass and cut when I have the loop on it's like a totally different amp..

I guess I am just going to have to be without a loop :roll:

I may try that bypass idea posted above. If I go that way I'll report back with the results.

Have you changed that capacitor I recommended yet?
If you haven't, you will always have that bass roll off until you do. The value of that cap sets the corner frequency of that tube stage for the loop. The smaller the cap value, the more low end gets shunted to ground and is therefore removed from your signal. The larger value I recommended allows the full guitar range to pass through the loop. This is actually a mod that Mesa recommended and the value is what they use when they do it. Otherwise, once those bass frequencies are removed from the signal, nothing else you try will add them back.

On the other hand, if you've already replaced it and still have the same issue, then you likely have another problem where something isn't working as designed. But if everything else is working properly, the cap should fix it. At least it has on every amp so far that I've done the mod to.

 

[Chiliphil1]

I have tried everything. I did patch cable, no patch cable, level max, level min, full wet, full dry, MV high channel low, channel high MV low. Nothing makes it sound the same as with the loop bypassed. It looses so much bass and cut when I have the loop on it's like a totally different amp..

I guess I am just going to have to be without a loop :roll:

I may try that bypass idea posted above. If I go that way I'll report back with the results.

Have you changed that capacitor I recommended yet?
If you haven't, you will always have that bass roll off until you do. The value of that cap sets the corner frequency of that tube stage for the loop. The smaller the cap value, the more low end gets shunted to ground and is therefore removed from your signal. The larger value I recommended allows the full guitar range to pass through the loop. This is actually a mod that Mesa recommended and the value is what they use when they do it. Otherwise, once those bass frequencies are removed from the signal, nothing else you try will add them back.

On the other hand, if you've already replaced it and still have the same issue, then you likely have another problem where something isn't working as designed. But if everything else is working properly, the cap should fix it. At least it has on every amp so far that I've done the mod to.

I have not had a chance yet, I am planning on it. I'll make an updated post once I have it done. I'm sure it will work I just have not been able to purchase the cap and do it yet.

 

[DS-1]

I had the same issue with my Road King v1 with it losing a ton of lows and low mids with the loop engaged. Looking at the schematics, it appears the loop design is nearly identical in your amp.

There is a 2.2uf capacitor connected to pin 3 of tube V4a (which is the effects loop recovery stage). Changing this to a 10uf tantalum capacitor should eliminate the tone suck or at least reduce it substantially. Just be sure to install it in the right direction with the "+" end connected to pin 3. This worked great for me.

Can you please post a picture of the mod?

Thanks a lot!

I will look when I get home this evening and see if I took a picture of it. Of course, mine would be on a Road King I, so if you don'thave the same amp, the location of the cap might be different, but there were a few different models that had the same design mistake.

I'll see what I can find in my pics though.

Thanks a lot!

I have a Triple Recto 3ch. The schematic is really similar to the one of the Dual Recto 3ch.

Did this mod changed a lot the sound of your Road King I using the loop? Do you think that the "tone sucking" is eliminated or reduced? Do you find any difference in sound using or not the loop?

Thanks!