Anyone build a stereo guitar amp with 3 OTs ?

[chopstuck]

I have a couple of donor chassis with 3 output transformers each. One Hammond a Conn and a Magnavox. You know the two moderate sized treble stereo channels and one big bass OT.

Anybody ever take advantage of one of these transformer sets to make a "HI FI" guitar amp with extra stereo imaging without the loss of out-of-phase low end ?

The odd thing is they all hook up to like two push-pull pairs.

Thinking of a 2x6 and 1x 15 combo cabinet of DOOM.

[Stevem]

The funny thing is that when you play a guitar thru something with a flat hi fi response guitars sound like shit.
Plug your guitar into your home stereo some day and see if you like it much!

[NickC]

My experiments with self-contained "stereo" guitar amps have been disappointing. Not wide enough sound field onstage to really impart the separation. A panning delay just doesn't pan wide enough in that configuration to impress. Just gets swallowed up with all the other sound sources onstage.

I use a tube amp (wattage depending on venue) for the center stage signal, the "main" guitar sound. Then run a mono line (derived from Pigtronix Keymaster) to a stereo effects rack, and from there route a stage-left and stage-right feed to a pair of Tech21 Power Engines for the effects. It yields a big sound with dramatic sweeps of FX.

0.02

[chopstuck]

Well thanks for the tips. So far one of my favorite niche builds is a RCA record player stereo with 2x SE 6Bq5's .
The circuit is a double Kalamazoo with that great 330k power tube gridleak resistor.

The thing just screams. Hifi parts don't have to be used in a hi-fi way. I tied off the UL taps and don't run any NFB.
I run either a 2x12 cab or 2x single 12" cabs. With a Roland chorus it sounds as big as the room. Loud too.

I may give up on the idea of using all 3 trannys at once.

Small stereo power amps are lots of fun to slave into as well.
I have some line level inputs I use with my effects unit.

Oh well. I will have to try something else with those giant low power boat anchors.

[Jack Hester]

Though I've never built this amp, I have an original GA-78RVT. You could model something from it.

You could also do something like the configuration that I've included, for a little stereo guitar amp that I plan to put in an old radio chassis of mine, with an internal speaker, and two external speakers. I have not finished with mine yet, but you can use it as an idea. I can't remember where I saw the original, but I modeled mine from one that has already been built.

Jack

[chopstuck]

Jack I love those amps. At one time I had 3 versions.
Their problem was when you drove both channels with one preamp it loaded that preamp down too much. I almost want to build one with two quads of EL84s and either a CF to drive them or another trick to get maximun driving voltage.
I'm probably just nuts enough to pull it off.

Marc

[LeftyStrat]

I have a Groove Tubes Space Station sfx mkii keyboard amp that has a novel approach. There is one front facing speaker and a speaker facing to the left but ported to both sides. The amp uses a technique similar to Mid/Side microphone placement. Front speak has L+R and side speaker L-R.

It can get a really spacious signal if is is elevated off the floor. Pittman licensed the patent to Fender and they use it in their acoustic guitar amps.

Here's the patent:

http://www.google.it/patents/US6219426