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Seperating Pre-Amp From Power Amp IN Amp Head?

Sloppyfingers

Member
Messages
1,157
Lets say, I wanted to operate on an Epiphone Valve Junior, would it be huge task to seperate the power section from it's pre amp section if I wanted to re-house the power section into a rack to use as a power amp only?

Not me of course..I would pay somebody..Just curious.

I just wanted to come up with a small tube power amp to run my pre amp pedals without having to carry an amp head around..I also want to slave it into my Fryette power station if need be..I was even thinking of getting a larger rack to somehow house both.

Sure there are still tube rack power amps out there, but nothing in a low power mono..They are all 20 watts stereo minimum..In a previous thread I toyed with the idea of tube headphone amps, but I'm not sure that would work, so I was just wondering about some of your thoughts on how extensive a job this tube head surgery would be..


Thanks ahead.
 

wyatt

Member
Messages
4,169
Because of the PCB construction, and the change of tube orientation to fit a rack, it would be *easier* to build from scratch.

You could reuse the transformers from the Epi if you wanted but due the the economies of scale, the overall project won't be as affordable as the Valve Jr was.
 

TimmyP

Member
Messages
2,488
By the time you put even a dinky tube power amp in a box or rack, it's going to be about as big and heavy as the head, so there is little if anything to be gained, and a lot of money to get it.

It would make more sense to just add a switching jack that would cut out the preamp and feed whatever is plugged into it to the power amp (jack tip to the power amp and switching leaf to the preamp output).
 

Sloppyfingers

Member
Messages
1,157
^ Thanks..Yes it does seem more trouble then what it's worth.

I appreciate all your input (pardon the pun).
I know Kingsley is coming out with a one watt power only in the new year, so I'll just wait.
I just wish that other tube pre amp manufacturers would come out with low wattage tube power amps in the el84-5 watt range.
Even el34 with power scaling.
I guess they went out of vogue.
 

lostpoet2

Silver Supporting Member
Messages
3,290
I think you just need to find a small amp you like with an effects loop and plug your pedals directly into the effects return. For example I think you could use the Peavey Classic 20 head this way and even use it 5w or 1w mode. Mick and Dan just experimented with this concept on That Pedal Show:
 

Sloppyfingers

Member
Messages
1,157
cool..I'll watch..Thanks!..I was trying to find a work around to having to carry a head or large expensive stereo power amp around, but no dice I think.
 

pdf64

Member
Messages
8,135
I don't see what the benefit would be from separating the VJ pre-amp and power amp?
The VJ pre-amp is as simple as could possibly be, just a simple flat response gain stage.
This feeds a volume control, then a second flat response gain stage, then the power tube.
So prior to the power tube, the only frequency / dynamic response shaping will be minor / secondary in nature, due to parasitic effects.
Just plug whatever you want to amplify into the input.
http://bmamps.com/Schematics/Epiphone/Epiphone_Valve_Jr._Schematic.pdf
 






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