Tube guitar head mods for bass?

[toneseeker]

Hello all,
I'm once again coming to the well of knowledge known as TB, in my never ending quest for improved tone.
A few months ago I found what I thought was a pretty good bargain and bought my first tube head. It's a 1970's 100 watt guitar head called the Peavey Rock Master (vintage tube series).
I had always been curious to try an all tube head and this one was cheap and relatively small and light.
Through a single 8 ohm 15" cab it has a nice warmth, presence, and midrange punch. The problem is it lacks good highs, lows, and that rich full sound I was hoping for.
I sometimes use it paired up with my solid state amps to add some warmth, fuzziness and midrange punch, but it just doesn't sound good on it's own.
I've recently contacted a tube amp tech that may be willing to try some mods for me. He looked up the schematics and said
"The amp topology does seem fairly typical. If there is reasonable access, it might be possible to make some small voicing adjustments to make the amp less midrangey." (he generally advises against mods on non point to point wired amps)
While I'm waiting to hear back from him I've been wondering what type of changes he can make (capacitors and resistors in tone stack?) and if it's worth it (I'm guessing around $60 per hr). This is all just speculative.
If this doesn't help I may look for something like a Trainer YBA-200 or Peavey VB-2.
One other kind of irrelevant question is: Do any of the new light weight Hybrid heads give the thick, rich tubey old school sound? All the ones I've heard so far sound pretty modern, crisp and maybe a little thin.
I'm looking forward to hearing comments and suggestions.
Cordially, Toneseeker.

 

[Jeff Scott]

I used to have a '66 Fender BandMaster head that Gerald Weber at Kendrick Amps modded for me for bass use. He replaced and adjusted some preamp caps and resistors, replaced the wimpy (for bass) output transformer with a Showman type he makes, added a bypass switch for the tremolo along with making the tremolo work on both channels, and put in new tubes, the power tubes being KT66s. This was the baddest BM on the planet.

 

[TheBassPreacher]

It'd be an interesting project, but it might end up costing you more than you would like.

As for non tube heads that sound thick and tubey, I've owned a number of tube amps in the past (Ampeg SVT-Classic, Mesa 400+ and Buster Bass 200, Traynor YBA-200, and I currently own a Peavey Alphabass head).... the best I've found to get that tube sound has been Markbass' stuff. With the VPF and VLE filters you can really dial in some nice warm tones. I've also heard the Tech 21 VT Bass pedal works pretty good and I recently recorded with the Tech 21 BDDI with some good results as well.

 

[anderbass]

The problem is it lacks good highs, lows, and that rich full sound I was hoping for.

I'm thinking you'd end up preferring a V4/V4B over your modded Peavey.

 

[B-string]

Almost gave any some secrets.......

 

[JimmyM]

I used to have a '66 Fender BandMaster head that Gerald Weber at Kendrick Amps modded for me for bass use. He replaced and adjusted some preamp caps and resistors, replaced the wimpy (for bass) output transformer with a Showman type he makes

i can almost guarantee that if you want that amp to be good for bass, a transformer replacement will have to happen. that would make the amp cost way more than it's worth. most guitar amps do have transformers that are wimpy for bass. that's good if you're looking for distortion, not so good if you're looking for clean output. personally, i wouldn't bother.

 

[T-Bird]

Hi.

i can almost guarantee that if you want that amp to be good for bass, a transformer replacement will have to happen. that would make the amp cost way more than it's worth. most guitar amps do have transformers that are wimpy for bass. that's good if you're looking for distortion, not so good if you're looking for clean output. personally, i wouldn't bother.

^This.

There is a way around it though.

Ask your tech to mod it to 50W by removing one of the PP pairs from both sides and relocating the OT tabs so the impedance labelling on the back and the correct OT tab matches. With halving the power, You drop the FEs of the OT by an octave. You'll lose 3dB, but that's easily "replaced" with an efficient cab and/or more speaker area.

Back in the 80's I made no mods to the JMP 1959 Marshall I had for bass, very good as is.

Regards
Sam

 

[jastacey]

I'd say just get the Peavey VB-2, it has pretty good EQ, it has a tube DI, it will handle 2-4-8 ohm cabinets, can get pretty loud, and it's priced right ... best of all you won't have to modify it