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If you run the amp clean, they can be helpful. If you run it dimed or thereabouts and use your guitar volume to control gain, they add mud. Which way do you run yours?
I've found that the right speaker change gets you 90% of the way there (C.Rex being the best thing I've found for them). A slightly larger cabinet made of real wood helps as well. That is with no circuit changes.
On the green board version, moving the verb return to pre-master is an EXCELLENT idea.
The power supply stiffening.......if you like a stiff feel at your strings, more similar to playing through a solid state amp, then by all means, do that.........not necessary and not helpful IMO.
Changing the mid cap to 15nf or even smaller will give you some kick in the low mids. It will also tend to make the amp a bit muddy when pushed into overdrive. You could also remove the "boxy" effect by reducing the size of the treble cap, which reduces high mids. There is absolutely nothing sacred about 250pf. Try 150pf or 120pf or 100pf. This method would also not add mud when pushed into overdrive. Or you could change the size of the slope resistor. There are a lot of ways to skin a rabit.
The jumpering of the mid pot reduces low mids and low end, which reduces mud, but that acts rather in opposition to lowering the value of the mid cap....
The NFB control is a good idea.
The little boost mod thing he has just tosses in another Ck to increase frequency response and gain of that stage. In opposition to what he claims, this does NOT give a boost when the amp is already in overdrive, it just adds gain. It also adds mud because the cap value he is using is 22uf, which is adding too much low end. 4.7uf would be plenty and probably still too muddy, 1uf to 3.3 uf would probably work better because the last thing you want with a "solo boost" is added mud...
Also, as Bruce notes, you have to be VERY careful with the lead dress.
Having played with a lot of amps that had those mods and messing with them on my own amp, my personal opinion is this: The presence mod is a good idea. If you have the green board version, move the verb return to pre-master for sure. The rest, not so much; some work at cross purposes or do undesirable things, many add mud to the ovedrive. My personal BJ is stock except for a presence control circuit wise, but it does have a C.Rex. It sounds great. I could mod the crap out of it if I wanted to, as I do to many amps, but I don't see a reason for it once the speaker was changed.
I've found that the right speaker change gets you 90% of the way there (C.Rex being the best thing I've found for them). A slightly larger cabinet made of real wood helps as well. That is with no circuit changes.
On the green board version, moving the verb return to pre-master is an EXCELLENT idea.
The power supply stiffening.......if you like a stiff feel at your strings, more similar to playing through a solid state amp, then by all means, do that.........not necessary and not helpful IMO.
Changing the mid cap to 15nf or even smaller will give you some kick in the low mids. It will also tend to make the amp a bit muddy when pushed into overdrive. You could also remove the "boxy" effect by reducing the size of the treble cap, which reduces high mids. There is absolutely nothing sacred about 250pf. Try 150pf or 120pf or 100pf. This method would also not add mud when pushed into overdrive. Or you could change the size of the slope resistor. There are a lot of ways to skin a rabit.
The jumpering of the mid pot reduces low mids and low end, which reduces mud, but that acts rather in opposition to lowering the value of the mid cap....
The NFB control is a good idea.
The little boost mod thing he has just tosses in another Ck to increase frequency response and gain of that stage. In opposition to what he claims, this does NOT give a boost when the amp is already in overdrive, it just adds gain. It also adds mud because the cap value he is using is 22uf, which is adding too much low end. 4.7uf would be plenty and probably still too muddy, 1uf to 3.3 uf would probably work better because the last thing you want with a "solo boost" is added mud...
Also, as Bruce notes, you have to be VERY careful with the lead dress.
Having played with a lot of amps that had those mods and messing with them on my own amp, my personal opinion is this: The presence mod is a good idea. If you have the green board version, move the verb return to pre-master for sure. The rest, not so much; some work at cross purposes or do undesirable things, many add mud to the ovedrive. My personal BJ is stock except for a presence control circuit wise, but it does have a C.Rex. It sounds great. I could mod the crap out of it if I wanted to, as I do to many amps, but I don't see a reason for it once the speaker was changed.
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