• 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.

What would you do with this amp?

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Please help. I recently bought an amplifier pulled from a Hammond P-40 tone cabinet. The schematic can be viewed here Just click "hammond", then "schematics" then scroll down to tone cabinets and click "P-40/Q-40".

I tried to attach the image but that never seems to work for me. If someone else can attach it to a response it will make viewing easier.

I would like to re-use as much as possible from the amp. I can replace the "treble" and "bass" transformers with single ended etc. Let your imagination go and tell me what you think!

Depends if the two output transformers are the same- i don't know if they are or not. If they are, then you could build yourself a stereo amp. edit- they look very different. Unfortunately you will need a pair the same. Maybe buy a pair somewhere.

But yeah, you will want to totally build a new circuit re-using that chassis. A good project! 6V6 in push pull is quite nice sounding too.

You cuold always get another whole amp and have a pair, these come up occasionally on ebay. Then you could bi-amp your speakers... 4 amps in total!
I think I'd try it the way it is first. just seperate the inputs and try it. Make sure the caps are OK first of course, but a PPP 6v6 output and 6sn7 difamp driver could sound good just the way it is. You can always change the transformers later.

Just remember, it's setup for balanced input right now so if you want to use it single input you will need to make some changes or build a phase splitter or something in front of the input.

Have fun.

Try it the way it is

Just seperate the inputs and try it

It would be really cool to fire this thing up. It is a 40lb monster of an amp. How would I seperate the inputs? It appears (from schematic) that pins #1 and #6 on the "Power and Input Signal" plug are the inputs. Would I simply connnect my left to #1 and right channel to #6?

I would like to try it the way it is, however, I only have experience with single ended (I've built an EL-84) amps and I am a little intimidated. The out put transformers are NOT the same. One (the bass) is significantly larger than the other (treble). I have some sacrificial speakers I could use to try it but I'm not sure how I would wire it up.
that amp has a balanced input. That means for example, pin 1s input signal could be + going voltage while pin 6 is - going, 180 degrees out of phase. That is what a balanced input is.

By spliting the amp input I was talking about driving the high frequency amp with 1 channel and the low frequency with the other channel. You will need to make some mods just to get it going. The low freq. amp doesn't have any DC blocking cap on the input and will need a ground reference for the grids of the 6sn7. I would change the cathode circuit too, most likely to match the high freq. amp.

If you still have questions about the balanced input do a search for "phase splitter" or "balanced line" or check "tubecad.com". Nelson Pass's site has a lot of info in this reguard aswell.

be careful but have fun
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