I'm about to rip the guts out of an old Peavey VTB-300 tube head.

[throbbinnut]

Yeah, I know, better to leave them vintage and all, but I think I've come to grips with the fact that this thing just doesn't sound all that great in its stock form when you're used to Ampeg. I rebuilt the power supply to spec just to get it playing, I've got USA 6550 tubes biased up right, and I've played it head-to-head with my Ampeg V4B through the same speaker cabs, and the Peavey just sounds hollow and too trebly no matter how I set the knobs. Actually the front panel says VTA-400, and the back says VTB-300, so it may be voiced for guitar, who knows?

I am ready to pull out the circuit board and build a Super Bass 2x12AX7 preamp in front of the original Peavey 6AN8+4x6550 output stage. I'm pretty dang sure that would be amazing.

Thoughts?

Chris

[Jim Campbell]

Originally Posted by throbbinnut

Yeah, I know, better to leave them vintage and all, but I think I've come to grips with the fact that this thing just doesn't sound all that great in its stock form when you're used to Ampeg. I rebuilt the power supply to spec just to get it playing, I've got USA 6550 tubes biased up right, and I've played it head-to-head with my Ampeg V4B through the same speaker cabs, and the Peavey just sounds hollow and too trebly no matter how I set the knobs. Actually the front panel says VTA-400, and the back says VTB-300, so it may be voiced for guitar, who knows?

I am ready to pull out the circuit board and build a Super Bass 2x12AX7 preamp in front of the original Peavey 6AN8+4x6550 output stage. I'm pretty dang sure that would be amazing.

Thoughts?

Chris

wouldn't it make more sense to add a new pre thru the power amp input.....if you really hate it,you might be better off to sell it and buy another amp.....

[faceinbass]

f*cking do it. If I had the knowledge, I would.

[T-Bird]

Hi.

Originally Posted by throbbinnut

Thoughts?

Chris

Determine first whether the OT is the reason for the hollow sound. Sounds like that from Your description.



Regards
Sam

[spankdaplank]

I had a VTA 400 for several years. Is yours the one with two channels that can be daisy chained via front panel jacks?

http://www.peavey.com/assets/literat...vta400_800.pdf

Even if the front end is different it sounds like the power amp is the same as the one I had.

I kind of had the same opinion about the tone. I tried using an Ampeg SVP preamp directly into the power amp. It required a small modification to add a 1/4" input jack to the power amp chassis.

If I remember, the results were fairly good. Tone wise it got me about 75% of the way there to Ampegish tone.
I agree that the output transformer might be the limiting factor.

Before I sold it I returned the amp to its stock configuration and was really digging it for its unique tone and the crazy channel stacking feature.

The deal breaker was the footprint of this monster: it seems like it was about 36 inches wide. The my (whatever) is bigger than yours so it must be better theory.

[throbbinnut]

The one I have only has 1 channel, but it's the channel with the Lo Accent and Hi Accent. I'm pretty sure the output transformer is standard and doesn't affect the tone in a bad way. The weird tone shape I think comes from the weird preamp circuitry - the Lo Accent, Hi Accent, and Presence controls are all local feedback tone controls in the preamp section (where part of the plate signal from a 12AX7 is brought around to the grid of the same triode as negative feedback through some tone-shaping circuitry). I don't like them. They sound bad and they should feel bad. I want a standard Marshall tone stack and standard gain structure. Plus this will allow me to add a Master Volume pot in front of the power amp.

Seriously, I'm gonna do it. It'll be rad once it sounds like a Marshall Major.

Chris

[christw]

Originally Posted by throbbinnut

The one I have only has 1 channel, but it's the channel with the Lo Accent and Hi Accent. I'm pretty sure the output transformer is standard and doesn't affect the tone in a bad way. The weird tone shape I think comes from the weird preamp circuitry - the Lo Accent, Hi Accent, and Presence controls are all local feedback tone controls in the preamp section (where part of the plate signal from a 12AX7 is brought around to the grid of the same triode as negative feedback through some tone-shaping circuitry). I don't like them. They sound bad and they should feel bad. I want a standard Marshall tone stack and standard gain structure. Plus this will allow me to add a Master Volume pot in front of the power amp.

Seriously, I'm gonna do it. It'll be rad once it sounds like a Marshall Major.

Chris

Standard as in it's big enough for the amount of power that the amp is pushing? You seem to know what you're doing from the sounds of it, so I won't question you on it.

Originally Posted by faceinbass

f*cking do it. If I had the knowledge, I would.

AGREED!!!

Seriously, amps are tools. So are basses. If they don't do what you want, you can make it better or get a new one. I like modifying things and making them my own.

[faceinbass]

Originally Posted by throbbinnut

Seriously, I'm gonna do it. It'll be rad once it sounds like a Marshall Major.

Chris

Yeah, you NEED to do this.

Keep us posted.

[Growly Lytes]

Please let us know how you end up going with this amp.Maybe show us a clip of it before & after if possible.

[BassmanPaul]

Please be VERY careful when working on a live chassis! We've kinda got used to having you around.

[jimmyjames77]

Sounds like a fun project. Do it! Putting a VT Bass in front of it, or through the loop, will get her ampeg sounding. I do it with my Classic 400.

[bassmanrocke]

I am really interested in hearing how this turns out. I know very little about amp mods, but part of why I love my Peavey basses so much is that they have so little collector value you can pretty much mod them however you choose(Though I haven't had to do too much)and not worry about the hit you'll take on resale.

[throbbinnut]

Alrighty, I haven't cut any wires yet, so I'll button it back up and make a "Before" video with it so I can compare once the mods are complete. Should be interesting.

Chris

[Growly Lytes]

As we say Downunder `Choice`

[kesslari]

Originally Posted by throbbinnut

Alrighty, I haven't cut any wires yet, so I'll button it back up and make a "Before" video with it so I can compare once the mods are complete. Should be interesting.

Chris

I've found this to be a darn good practice.
I'd also join in with those who say "try running an external preamp into the power amp section" and that way you can see if you really like it before making the changes permanent.

[Growly Lytes]

Anything yet brother ??