Stereo Hi-Fi amp into 36 watt amp?

[JonFrum]

I have a 4xEL84 stereo phono amp I'd like to use for a 36 watt build. I thought I had seen someone say they had built a 2-OT 36 watt amp, but I can't find it now. I'd run it mono, so I'd need some help with the wiring on either side of the OT.

[Mooncar]

I second that request.

[Andrew4566]

For the proper way to wire the 2 OT's look at some of the silvertone(sears) schematics at schematic heaven. The twin twelve may have been the one I saw that had that set-up.

-Andy

[rjgtr]

Or better yet why not run it in stereo?

You could have a stereo effects loop feeding two phase inverters. Think of the possibilities. Gibson had a stereo amp that had one side clean and the other side with reverb. You could wire a 2x12 cabinet so one side is dry and the other is wet. Or use a foldback reverb driven from one OT side and returned to the other. Then you won't have the oscillation issue and can make the reverb really full.

Oh there's just so many possibilities...

[dartanion]

I have been working on a 36watt design that I had considered 2 OTs, but have chosen a single OT for simplicity. Although it is a 2PI arrangement with an 18watt + 5E3 power section.

A stereo 36watt would be cool though. And it sould be an easy conversion from what you have, just preamp mods to what you want.

[Strat]

I'm pretty sure Graydon's first 36W was built with two 18W transformers so I'll expect he'll help out with the wiring. I would guess that as the 18W primary is 8k and for a quad of 84's it needs to be 4k that you would simply parallel all the primaries and secondaries, unless of course you go with the stereo option.

[toyota_tim]

I run an old Knight stereo hi-fi amp rewired as a stereo 18w+18w.
It has a stereo effects return that uses the second input on each PI. This way the effects are run full wet in parallel. The dry signal is untouched by the loop. Using switches already on the chassis I can switch to wet only for effects like stereo chorus, or 1 channel dry and 1 channel wet like was mentioned above.
Only draw back, you always need 2 speakers hooked up. My plans are to build large head cab with 2 small speakers built in that will switch out when I pug in the externals. Lately I have been running this amp into a pair of Altec 1207c's (6x8" columns)

[Wannatone]

I'm pretty sure Graydon's first 36W was built with two 18W transformers so I'll expect he'll help out with the wiring. I would guess that as the 18W primary is 8k and for a quad of 84's it needs to be 4k that you would simply parallel all the primaries and secondaries, unless of course you go with the stereo option.

Just remember that you'll have to connect 2 speakers. To be more precise, you'll have to run the dual OT amp at half of the 'single OT' speaker impedance. Paralleling OT's aint change the winding ratio.

Think about it. If you have a 12 V mains transformer and a 12 V bulb... then connect a 2nd mains tranny in parallel... that bulb aint burn any brighter as you still have 12 Volts... but now you can connect two bulbs because you have doubled the currrent capacity using a 2nd tranny. Right?