R2 Gain mod? & Noob R2 mod question..

[robredo_mattila]

Does anybody have a schematic for the R2 gain mod? I know the R2 Volume mod is easy to find info about, but I want to do the Gain mod at the same time.

Also, my R2 channel is quieter than R1 and I balance my Lead channel to be the same as R2 then I roll down my guitar volume control for quieter clean tones. Doesn't the R2 volume mod only reduce volume since it is a passive 250k pot? or does it boost the volume? maybe my Purple stripe Mk. III is faulty in that case?

...

 

[CoG]

You're bypassing a resistor with the new pot, though.

I find that after the R2 volume mod, if I have Volume on 7 and Lead Master on 5, I only need the R2 Volume on about 6.5 to balance.

Do the R2 volume mod first, it's easy. You *may* not want more gain on R2 once you get to play with it a little with the volumes matching.

 

[robredo_mattila]

You're bypassing a resistor with the new pot, though.

I find that after the R2 volume mod, if I have Volume on 7 and Lead Master on 5, I only need the R2 Volume on about 6.5 to balance.

Do the R2 volume mod first, it's easy. You *may* not want more gain on R2 once you get to play with it a little with the volumes matching.

Ok, thanks for that. So basically having R2 quieter than R1 (in stock form) is normal?

 

[CoG]

Yeah, my greenie was like that before I did the mod.

 

[robredo_mattila]

Yeah, my greenie was like that before I did the mod.

Great, I thought I had a bad tube. Obviously not! :twisted:

 

[camsna]

Nope. Totally normal. Albeit strange that Mesa would release it like that.

I agree. Do the R2 mod. After you do, R2 is one of the coolest sounds I've heard from an amp. Sure doesn't need any more gain!

 

[robredo_mattila]

Nope. Totally normal. Albeit strange that Mesa would release it like that.

I agree. Do the R2 mod. After you do, R2 is one of the coolest sounds I've heard from an amp. Sure doesn't need any more gain!

Cool, I was thinking more along the lines of adding another pot (or using the direct out space on the chassis) to control the overall gain level of R2 seperately from R1/Clean If that's possible?

 

[robredo_mattila]

Last quick question, is the stock reverb pot 250k ?

 

[robredo_mattila]

Well I did the mod, it makes a world of difference. I used the existing reverb pot (which I think is 25k instead of 250k?) and I left the shield wire going to one side so it's silent on 0 and 10 and it's loud in the middle, works best on about 7 or so.

I also built a quick footswitch for the Graphic EQ using an SPDT. This amp just keeps getting better 8).

Now, has anybody modded the FX loop from Series to Parallel?

 

[camsna]

Well I did the mod, it makes a world of difference. I used the existing reverb pot (which I think is 25k instead of 250k?) and I left the shield wire going to one side so it's silent on 0 and 10 and it's loud in the middle, works best on about 7 or so.

I also built a quick footswitch for the Graphic EQ using an SPDT. This amp just keeps getting better 8).

Now, has anybody modded the FX loop from Series to Parallel?

I don't know the value of the reverb pot. But the R2 Volume pot definitely needs to be 250K.

About modding the loop to parallel. I don't think anyone has. Or would. Your better off with a line mixer of some sort. Problem with the Mk III loop, though - is that it's send level is in-between consumer level (-10) and line level (+4). It's more like -2. So it'll clip the crap out of your pedals. And your line level gear will have to amplify the signal, which adds noise.

I've been pouring over and over what to do about that. I talked to John Suhr, who is going to mod my amp with a new, proper loop

 

[Restless Rocks]

I'm certain that there are LOT'S of players including myself who run various stock pedals in the FX loop of Mk III's and IV's without any signal level or tonal problems. The Mk III was designed so that R2 would be nicely balanced when the input gain is set around 6 - 7. Now many of you go for more R2 gain by maxing out the input gain and using front end boost etc. Hense the need for the R2 master mod. The signal level at the FX output is varied by the clean gain level (notice the MkIII R1 stays nearly clean even when gain is maxed) and the Lead Master. Much the way the Channel Masters set the FX send level on the MkIV. When the MkIII amps were designed most guitarist of the day were satisfied with the gain structure as stock, now many guys push for more extreme gain settings hense unbalancing the preset level of R2

 

[robredo_mattila]

I don't know the value of the reverb pot. But the R2 Volume pot definitely needs to be 250K.

About modding the loop to parallel. I don't think anyone has. Or would. Your better off with a line mixer of some sort. Problem with the Mk III loop, though - is that it's send level is in-between consumer level (-10) and line level (+4). It's more like -2. So it'll clip the crap out of your pedals. And your line level gear will have to amplify the signal, which adds noise.

I've been pouring over and over what to do about that. I talked to John Suhr, who is going to mod my amp with a new, proper loop

That's good to know, I have thought about getting a Suhr Minimix to use with a delay unit. Currently I use a Boss RV-2 reverb/delay in the loop and it sounds ok. However I tried an old Dod flanger in the loop and it just distorted like mad.

 

[robredo_mattila]

I'm certain that there are LOT'S of players including myself who run various stock pedals in the FX loop of Mk III's and IV's without any signal level or tonal problems. The Mk III was designed so that R2 would be nicely balanced when the input gain is set around 6 - 7. Now many of you go for more R2 gain by maxing out the input gain and using front end boost etc. Hense the need for the R2 master mod. The signal level at the FX output is varied by the clean gain level (notice the MkIII R1 stays nearly clean even when gain is maxed) and the Lead Master. Much the way the Channel Masters set the FX send level on the MkIV. When the MkIII amps were designed most guitarist of the day were satisfied with the gain structure as stock, now many guys push for more extreme gain settings hense unbalancing the preset level of R2

Very helpful and insightful, thanks!