• WARNING: Tube/Valve amplifiers use potentially LETHAL HIGH VOLTAGES.
    Building, troubleshooting and testing of these amplifiers should only be
    performed by someone who is thoroughly familiar with
    the safety precautions around high voltages.

Converting tube guitar amp to Hi-Fi amp

I don't know, depending on what he has a lot of it could probably be used.

Starting with the assumption that you don't need to get as high of output as the guitar amp had you should be able to use...

- Chassis
- PT
- Output tubes (if only two you do SETSP, if four PP)
- All of the sockets

You might be able to get away with using the preamp tubes but a few bucks for more appropriate tubes would not be unreasonable.

Whether this is a reasonable thing to do is of course another matter. It might indeed be most cost effective to sell the guitar amp and use the proceeds to build a hi-fi amp but I think that "you can't get there from here" is a bit of an over statement.

As a matter of fact I have ordered two of the populated chassis that Drew Druncan us selling on the AX84 forums so that I can build a guitar amp with one and use the other for an electronic crossover and SETSP for my stereo. Instead of the 12AX7s that will be in the guitar amp the home amp will probably use something like 6N1P or 6922. 6V6, 6L6 or several other octal options can be used for output tubes. The existing PT is perfectly adequate and a pair of edcor OTs are only about $40.

I looked up the schematic in question and it is PPP using four EL34s one PI tube and two preamp tubes. It seems to me that with the right coice of tubes he could even do a nice PP amp using one 9pin tube socket for the initial gain stage for both channels. Use the other pre amp socket and the PI socket for LTP PIs or use cathodyne PIs and free up the other pre amp tube socket for something else.

Seems to me like a lot of potential there.



2008-02-27 10:04 pm
converting tube guiter amp to hi fi amp

Thanks for your response guys; I have a couple of other tube amps that I can salvage for additional parts if need be, I wanted to check with the experts out there, if it was just a matter of changing out and adding additional components to the pre amp stage to make the conversion.

My other plan is to build a fairly high powered audio amp using 6550 tubes on the output stage, any ideas where I could get a schematic?


2008-03-04 2:00 pm
without dis-mantling the amplifier, use a 1meg ohm resistor in series at the quarter inch jack side. This will allow you to use a cd player or cassette deck on your guitar amp but the fidelity will not be all that great as it is designed for the guitar impedences.


2008-02-27 10:04 pm
Thanks Korey, thats a start! I envisaged adding and changing a few of the front end components i.e. resisters and caps to smouth out and improve the overall quality of the amp.

Its just knowing what and where to apply changes to take of the rough edges. This would be my first stage project before attempting to build from scratch.
EC8010 said:

Sell it and use the money to buy a Hi-Fi amplifier. :D
Seriously, it can't be done; the two are quite different.


I completely agree with the above, and butchering a guitar amplifier
for parts whilst possible, you would need two of them for matching
output transformers, and there is no guarantee they are suitable.

Besides I doubt you could design an ad-hoc valve hifi amplifier
that made the best use of the disparate parts available.

Using the clean channel and messing with the inputs would probably
make a decent sounding mono amplifier for PA vocals for a group,
but proper hi-fi ? forget it - as said they are very different beasts.

I used 4K P-P Chumacher guitar output transformers (made for ADA guitar amps) for Hi-Fi and vocal amps, they sound nice. At least, highs are better than with bigger transformers made for Hi-fi. I used paralleled 6L6 tubes, 375V plate voltage, 315V regulated screen grid supply, obtaining 50W from guitar transformers made for 80W output. You may try that.

What is more critical, is a driver stage before output tubes: guitar amps made such a way so driver stage produces harmonics, the louder the more, to add dynamics to plain electric guitar sound. You don't need them for Hi-Fi.


2004-09-19 12:45 am
I would strap the output tubes as triodes as first thing.
You will get a wider frequency response as result of the summing factors: the output impedance is lower and less output power.

After this, get rid of tone stack and lower the gain of the preamp section.
Pay attention to the drivers, they must be able to drive the output tubes without distortion, unlike guitar amps.