Express preamp for bass guitar?

[Abstract]

Hell Yeah!!!


For the last few days I've been messing around with my new 2x7189 express/liverpool. It seems to be calming down a bit and not misbehaving so much (or I may just be going deaf, and getting better with the amp). So far, I've been having a blast just playing with the distortion and feedback potential. It goes without saying that it sounds very nice.

I'm a bass player first and foremost, but I'm pretty heavy into guitar as well. For giggles I decided to try this amp out with my #1 bass today. I shouldn't have done that. Now I have to figure out how to get a bass amp version of an Express made. I'm not sure I can turn my old amp back on. I turned my Reissue Fender Bassman on the other day (back to back with the 'Wreck) and it sounded like shit. I never should have bought this amp. It's ruining me for everything else.

So I guess my real question is, has anyone ever made a KT88 or 6550 "Express"?

[Abstract]

The search function gives me an error message.

[leaveitalone84]

I'll try to field this.

From my limited knowledge on the express the power amp is biased a little cold so it saturates early because the preamp has a lot of gain. The preamp has a lot of distortion too.

If you paired the preamp with a bass amp power section you may get something pretty cool. You'll get preamp distortion thou.

See if you can find a Traynor YBA-1 Bass Master head. I think you can still find them relatively cheap. You could probably mod the preamp into an express.

[Wayne]

See if you can find a Traynor YBA-1 Bass Master head

Say - I picked up one of those recently & was trying to decide what to do with it - now I have another idea. Thanks

W

[Abstract]

I'll try to field this.

From my limited knowledge on the express the power amp is biased a little cold so it saturates early because the preamp has a lot of gain. The preamp has a lot of distortion too.

If you paired the preamp with a bass amp power section you may get something pretty cool. You'll get preamp distortion thou.

See if you can find a Traynor YBA-1 Bass Master head. I think you can still find them relatively cheap. You could probably mod the preamp into an express.

Thanks for the reply.


Do you mean that you've heard of people modifying the preamp of a YBA-1 to Express specs...or do you mean that you believe that it could probably be done?


I'm perfectly comfortable with distortion, no matter the source, as long as it's as musical as my 2xel84 amp and I can clean it up with the volume knob.


I think a 2x6550 or 2xKT88 would be the bomb. I'm sure it would be a pain to build, as it's probably fairly uncharted waters. Anyone wanna try....cheap?

[Zippy]

Why not stick to the family of output tubes? 2xEL34 (Express) or 4xEL34 (with perhaps a higher plate voltage on the power stage but keeping the classic voltages in the preamp)?

[Abstract]

Why not stick to the family of output tubes? 2xEL34 (Express) or 4xEL34 (with perhaps a higher plate voltage on the power stage but keeping the classic voltages in the preamp)?

Thank you for the reply,


The ONLY reason is my affection for 6550 breakup.

I used to have an old 70's SVT with 6550's and I loved the cranked tone...I figured 1/3 power would still be a fair amount of power. It's sale afforded my fixed bias Liverpool. The amp that started this thread.

Besides, I've not heard an EL34 based bass amp, though I know they exist. Perhaps an EL34 amp would be perfect...I think it's more the preamp that I like the sound of. It's a bit thin with bass so I'm thinking some tweaking of the preamp would be necessary...not a LOT of tweaking, but as far as controls, the bass center frequency could be an octave lower. I'm not at all sure what's involved with this, and couldn't even speculate...

The mids and treble could be lowered too (not a dealbreaker), and the presence can go away. It needs to be as hiss free as possible.


...a guy can dream can't he?

[Structo]

I'm not a wreck guy so to speak but, from what I have read, the Express amps operate on the verge of insanity, pushing the power tubes into early saturation and distortion.
Seems that most bass players go for a clean tone with huge headroom and power.
Then if they want dirt they use a pedal or two.
I'm not a bass player and I don't play one on TV.
Just sayin'.

[Zippy]

The ONLY reason is my affection for 6550 breakup.

I used to have an old 70's SVT with 6550's and I loved the cranked tone...I figured 1/3 power would still be a fair amount of power. It's sale afforded my fixed bias Liverpool. The amp that started this thread.

Besides, I've not heard an EL34 based bass amp, though I know they exist.

Ah, OK. That was exactly why I chose the EL34 quad - for the breakup quality. If you're into the 6550, there's your answer. I actually mod'd an SVT several years ago (last century!) to run EL34s. It was a pretty sweet voice but not intended to overdrive such as a 'wreck front end would. Given the way that an Express has a clean-to-distorted continuum, I would tend to go with an output tube that acts the same way. The 6550 might be interesting but I would anticipate it to act very differently.

[Abstract]

I'm not your normal bass player.

I lean heavily into Primus and experimental guitar influenced bass. Lotsa chords and dirt. Not Cliff Burton Anesthesia distortion, but more tube breakup than a little.

Mainly with active pickups (preamps).

So I can REALLY drive a circuit hard.


Man it's been a busy week, I'm gonna get off the comp and go play bass thru the wreck again. It sounds great, just could be a little thicker in the very low registers.

BBL

[rfgordon]

The Express preamp is very basic, so it should work well for bass--but you might want to fatten up some of the coupling cap values. This preamp into a pair of 6550s or KT88s into a bigger OT with more bandwidth (I'm thinking one of the Dynaco style OTs) would probably make for a killer club-size bass amp.

[Abstract]

The Express preamp is very basic, so it should work well for bass--but you might want to fatten up some of the coupling cap values. This preamp into a pair of 6550s or KT88s into a bigger OT with more bandwidth (I'm thinking one of the Dynaco style OTs) would probably make for a killer club-size bass amp.

My thought's EXACTLY.

I just don't know what needs to be adjusted.

[dartanion]

The Wreck preamp is all wrong for bass as well the power section is designed to sag/swell, and distort. You need a much bigger power supply and design for clean in a bass amp. It would be cool to try it, but it's probably not going to resemble a Wreck when you're through tweaking it. Stock, I would think it would be really mushy and distorted with whatever power tubes you run in it.

[Abstract]

The Wreck preamp is all wrong for bass as well the power section is designed to sag/swell, and distort. You need a much bigger power supply and design for clean in a bass amp. It would be cool to try it, but it's probably not going to resemble a Wreck when you're through tweaking it. Stock, I would think it would be really mushy and distorted with whatever power tubes you run in it.

I think you're probably right.

But that's great because I'm not really looking for the solid state tight thump...but instead, more of a tubey, saggy Jbass grind.

I like the TW preamp because it's so transparent. The grind comes from the power tubes right? I'm saying I like the way the circuit sounds now, and I think it could be a bit better with a fatter bottom. Perhaps the 6550's will take care of that.

Is it a p.i.t.a. to work 6550's into the power sections (edit: and still have it sound like a 'wreck)?

[dartanion]

The issue with a straight express would be that it would break up too much for bass. There is quite a bit of sag in the power supply when hitting it hard with guitar, now try hitting it with bass frequencies. I just think it'll be too mushy. I'd try it with my express, except I don't own a bass.

FWIW- I use my 69 SFTR for bass quite frequently and it does the light crunch tube sound with a bass.

Hiwatts and 1986s are another good option or starting point for that bass tone.

If you really wanted to do a bass Wreck, over spec the transformers, and probably crank the plate voltage up to around 500-600V. It takes a lot more power to produce bass frequencies, so you'll need the extra oomph or it may be too squishy.