Peavey Classic 400 - Mega Thread - Part II

[Nighttrain1127]

Explain on why you would not use KT-88's please . I have read about Many people using them with good results. Not challenging you here but there has to be a reason you would go 6550's instead. So If I retube with all JJ's in the pre it won't matter?

 

[nashvillebill]

I put EH KT88's in mine. Realistically, they're 6550's, specs are the same. They sound good though and there's plenty of Crunch.

Perhaps a previous owner put in a different preamp tube and lowered the gain in the Crunch channel? Or put the 12AT7 where a 12AX7 is supposed to go?

 

[CL400Peavey]

Explain on why you would not use KT-88's please . I have read about Many people using them with good results. Not challenging you here but there has to be a reason you would go 6550's instead. So If I retube with all JJ's in the pre it won't matter?

You want less head room. Not more.

 

[Nighttrain1127]

I Had a tweed Classic 400 a few years ago that I sold but when I had it if you used the crunch channel with restraint on the gain it would crunch and not get all tube pre Buzzy like it could if you cranked the gain on the crunch channel. That is what I am looking for . I am not looking for Pushed SVT type grind . Maybe I would be better off with a Darkglass vintage microtubes in front of the pre

 

[CL400Peavey]

I Had a tweed Classic 400 a few years ago that I sold but when I had it if you used the crunch channel with restraint on the gain it would crunch and not get all tube pre Buzzy like it could if you cranked the gain on the crunch channel. That is what I am looking for . I am not looking for Pushed SVT type grind . Maybe I would be better off with a Darkglass vintage microtubes in front of the pre

Then tube it the way your old one was?

I am confused as to what the issue is.

 

[Nighttrain1127]

I don't know how it was tubed ( Not that i don't appreciate the help but) If I did I would have done that and not asked here . That is the Issue I no longer have the old one to go by. I guess I can just retube by the chart and see what happens. I didn't know if someone had some luck with some tubes and not so much with others. Guess not so Thanks for the help

 

[CL400Peavey]

Re tube the power section if you want different break up there. If you want something else out of the pre change those tubes. It makes no sense to change the power section tubes if you want to change the tone of the pre.

 

[eldoryder]

Dad-Blast-It!!!! EVERY freakin' time I find a deal on one of these "bucket list" amps, it is ALWAYS on the other end of the Earth. For anyone in the Virginia Corridor, here's a 13-day-old Craigslist Ad for a Classic 400. The guy only wants $400.00 for it! Don't know any other details than that, but here it is.

PEAVEY CLASSIC 400 CL Lynchburg, VA 0.00!!!! | TalkBass.com

[Invalid or Expired Link Removed]

Good luck, somebody.....may my sorrow at being too far away be your victory for being in the right place at the right time!

Mike in Texas

 

[metron]

Oh man this thread. I had two over the years. A NOS one and later another used one. Maybe it was the other way around. I have never heard or felt a fatter syrupy bass tone through my NV610 cab. That includes a vintage SVT, DB 680/728, and the DB 750 though they all were close. It was fun. About as visceral as bass gets though ultimately I found it prohibitive for gigging.

 

[groovaholic]

Back in the saddle!

Here's a gut shot--"the belly of the beast" as I start some minor mods, updates, and tweaks...

 

[Basshappi]

Oh yeah!

 

[CL400Peavey]

Back in the saddle!

Here's a gut shot--"the belly of the beast" as I start some minor mods, updates, and tweaks...View attachment 742569

I knew you couldnt stay away for long. What mods are you doing?

 

[groovaholic]

I knew you couldnt stay away for long. What mods are you doing?

Basically, I’m doing all the same functional mods as I did to my last Classic 400:

• Replace the power cord (ground pin was broken off)
• Remove the fan (the wooden front panel was already removed)
• Add a Speakon output
• Add a chassis-mounted bias adjustment pot
• Retension the tube sockets
• Install spring retainers on the KT-88s
• Replace the preamp tube retainers with shorter ones that fit better

Then some cosmetic stuff like installing “chicken-head” knobs, cleaning up some corrosion on the chrome, etc.

The amp had a blown tube, so I removed half of them while I waited for the replacement, and the amp STILL sounded big.

I'm anxious to get it nursed back to full health!

 

[tombowlus]

Those sound like nice tweaks!

 

[CL400Peavey]

Basically, I’m doing all the same functional mods as I did to my last Classic 400:

• Replace the power cord (ground pin was broken off)
• Remove the fan (the wooden front panel was already removed)
• Add a Speakon output
• Add a chassis-mounted bias adjustment pot
• Retension the tube sockets
• Install spring retainers on the KT-88s
• Replace the preamp tube retainers with shorter ones that fit better

Then some cosmetic stuff like installing “chicken-head” knobs, cleaning up some corrosion on the chrome, etc.

The amp had a blown tube, so I removed half of them while I waited for the replacement, and the amp STILL sounded big.

I'm anxious to get it nursed back to full health!

Those sound like nice tweaks!

The functional mods are all items I would love to have done to mine down the road. Would really love the speakon jack.

 

[groovaholic]

The functional mods are all items I would love to have done to mine down the road. Would really love the speakon jack.

The Speakon is relatively easy to add; there's a perfect space for it just to the left of the 1/4" jacks.

Ideally, I'd have replaced one or both of the 1/4" jacks with Speakon combo jacks, but the 1/4" share a PCB with the impedance selector switch and some other circuitry I felt it best not to mess with...

But adding an easy-access bias pot is really the heart of the matter -- that little bias trim pot means that you have to bias the amp while its disassembled, then (supposedly) wrestle that 85# monster back into the wooden case without damaging any of the tubes.

It is NOT practical.

 

[groovaholic]

Here's pics of the Speakon and bias pot locations that I mean:

 

[nashvillebill]

....
But adding an easy-access bias pot is really the heart of the matter -- that little bias trim pot means that you have to bias the amp while its disassembled, then (supposedly) wrestle that 85# monster back into the wooden case without damaging any of the tubes.

It is NOT practical.

IIRC, I was able to slide the amp partially out of the wooden case, but not all the way, and access the pot. Still a pain but possible.

The manual stays that the amp must have exactly 120VAC power supply for an accurate biasing, I believe. I used a constant voltage supply but a Varian with a meter would work.

 

[groovaholic]

I'm replacing it with a Vishay-Spectrol 10-turn precision potentiometer -- not nearly as touchy and lets me check bias without any disassembly beyond what would be required to change tubes anyhow.

Also, I set bias with plate current, not the bias voltage in their spec -- using the voltage spec tends to result in a really cold bias, where I prefer it in the 60-65% range.

 

[nashvillebill]

Also, I set bias with plate current, not the bias voltage in their spec -- using the voltage spec tends to result in a really cold bias, where I prefer it in the 60-65% range.

I don't think I saved the discussion, but there was a long debate about setting up this amp on one of the repair forums I hang out on, several of the senior techs didn't advise using plate current on this amp. I'm going from memory, it was a couple of years ago so I don't remember specifics but their comments seemed logical.

Perhaps BobbyBld can comment.