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Magnavox 93 series ideas

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drewski13

New Member
Hello! I have a 93 series Magnavox stereo amplifier. I was planning on restoring it and using it as a desktop amplifier but I recently had another idea. I'm very much into tube guitar amps and wondered if this amp would be a candidate for conversion. It uses a tube set that would likely be considered odd for a guitar amp, but I'm not sure useless. I would plan to add a fender style tone stack to the circuit to help shape the frequency curve. I would output each channel to it's own speaker in a 2x10 or 2x12 cabinet. Am I way off base with my thinking or could I make this work? Any thoughts are welcome! Thanks!
 
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I'm not sure it's that odd....the 6BQ5 is the same as an EL84, and the 6EU7 is the same as a 12AX7. I have at least two guitar amps in my collection that have the same compliment of tubes. I'd say, though, that since this is a hi-fi amp, getting large amounts of distortion may not happen in stock form....my guess.
 
I dunno, I've seen EL84 guitar amps before. The 6EU7 driver tubes are the same as a 12AX7 with a different pinout. It could be easily rewired for 12AX7's or just use socket adaptors.
 
Not sure I see the point in using a stereo amp for this. Usually mono amps are the choice just because you don't need 2 channels of amplification. That and what else do you do with a mono amp if you don't have a mate and aren't into mono records? PA amps are also a popular choice for this.
 
Actually, I can think of at least one use for this in the guitar world. While I love plugging straight into my tube amps, I do sometimes require the use of a Line 6 X3 live. I would not be beneath using a 93 series maggie as the power amp for this. It would be quiet, not color the output of the processor, and look super cool. I know, purists would scoff at putting any sort of modeling gear in front of an all tube power amp, but if it works, it works.
 
I'd save the Maggy for audio/stereo duty, specially if its complete,,, either rebuild it or pass it on... Lots of mono audio/PA amps available really cheap (hamfests, antique radio shows etc) that would make good guitar amp stock, a lot of PA amps have more than one input circuit also...
I got guitar amp schems online and built four git amps from scratch...
Just my opinion,,,,its your Maggy to do as ya please,,,,
Have fun!
 
I would keep it completely stock if I had received it in working condition. I got this thing for cheap and it was basically just the chassis and transformers. Most of the wiring had been cannibalized and the power tubes were broken(as in the glass was cracked or had shattered). I did end up with the original pre-amp tubes as well. So since it was already so trashed I thought I might make a neat experiment out of it. So my thinking is having the option to run either stereo or mono input with a stereo speaker cab. I'd like to add a volume and tone stack as well, though I know that will reduce the gain from the pre-amp stage. The chassis has an additional pre-stamped hole that would easily accommodate one more 12AX7 that I could possibly use to mitigate the loss of gain from the tone stack. Then again, since the amp was thrashed when I got it I could also just build a guitar amp on the chassis. I guess I thought it would be neat to at least use most of the original circuit for the idea since I do have the transformers and chassis. I appreciate all of the feedback and ideas and more are always welcome. Thanks everyone!
 
It's not often discussed here, but the output transformers in console stereo chassis aren't greatly different from guitar amp OPTs. That is to say, they're generally deficient in performance at very low and very high audio frequencies. Of course that made 'em cheaper to manufacture than true hi-fi OPT's, but there was at least one other reason: Acoustic feedback from the speakers to the turntable in a common cabinet usually causes massive oscillation unless the lowest frequencies are attenuated.
 
If you've got a chassis with transformers, you have a perfect excuse to modify it per Dave Gillespie's re-work of the circuit. I have one of those on the bench currently that I'm working on for another member here. Came to me as a basically stripped chassis, which honestly makes it easier to work with. Nothing in the way, just clear up the solder connections so its a blank slate and go for it.
 
gadget73 said:
If you've got a chassis with transformers, you have a perfect excuse to modify it per Dave Gillespie's re-work of the circuit.
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DG's re-work of the circuit really takes the 9300 series, and makes it sound like an actual high-fidelity tube amplifier...that's my take...
Even with the original output transformers...
 
If you see the stock measured performance vs modified, there isn't a lot to insinuate. Its just better with the phase inverter modifications and the EFB setup in terms of frequency response, power output, and distortion performance. There are other mods for these but I don't believe any of them have documented performance results.
 
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6DZ7 said:
Gadget, what you have just said means what? Better? The insinuation is that the original amp is not in the HI-FI category.
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I'm just saying that it can be made to perform better than it does stock. Don't read into it too much.
 
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