Comverting a Rockmaster preamp into a TB Raxx

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dicianne
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Comverting a Rockmaster preamp into a TB Raxx

Post by dicianne » Wed Jan 19, 2022 9:23 pm

I have a rockmaster preamp to spare. And I was thinking to convert it to a TB Raxx
How dumb of an idea is this. And is it feasible.
This is essentially the same as the TG Raxx isn't it? what parts were changed specifically?
Thanks

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Enzo
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Re: Comverting a Rockmaster preamp into a TB Raxx

Post by Enzo » Thu Jan 20, 2022 1:54 am

The difference between the TBRAx and the TGRax is two capacitors in the tone stack...that's it. C103 and C106.

The Rax's have two tubes, the Rockmaster has four. The Rockmaster as a far more complicated circuit. The Rax has a gain switch that gives a boost in one stage. Rockmaster has additional gain stages for the dirt channels. The Rax are nice little tube preamps, but kind of a one trick pony. I should think you could get anything the Rax can do out of the Rockmaster...and a whole lot more.

It wouldn't be a modification I would recommend to a client.

dicianne
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Re: Comverting a Rockmaster preamp into a TB Raxx

Post by dicianne » Thu Jan 20, 2022 8:20 am

Hi Enzo, Thanks on that info regarding the difference between the TG/TB

Now what would you change in the rockmaster to extend the bass frequencies in the clean channel. I don't care if the mods incidentally affect the dirt channels as well. I don't use distortion that much on bass

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Enzo
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Re: Comverting a Rockmaster preamp into a TB Raxx

Post by Enzo » Thu Jan 20, 2022 6:41 pm

Beats me, the main caps for passing along signal are already fairly large values. There are maybe two caps that could go from 0.047uf to maybe 0.1uf, but I don't know that that would get you far. You could possibly add cathode bypass caps to a couple stages, but that also makes them gainier, and might even make it muddy. This isn't really the stuff I do. Left up to me, I'd likely consider adding an EQ between preamp and amp. Either pedal or rack mount.

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