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Magnavox 185/175 with 6l6G tubes?

century tek said:
Member GordonW uses 6L6GC's in Magnavox amps he has supped up. Maybe send him a PM. He would give good tips on how to rebuild the power supplies and such.
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Not with these output transformers. Mine use the heavier outputs, found in the AMP101/AMP128/AMP132/AMP142/AMP150/AMP179 amps (the PPP 6V6), which are fine with a pair of 6L6s (one pair of 6L6s can provide about the same power output as a quad of 6V6s).

The AMP175/AMP185/AMP164/AMP169 outputs can actually be saturated in the bass, with an optimized single pair of 6V6s. There's no real reason to use 6L6s- these transformers will just saturate at an even higher frequency, as you force more power out of them...

Regards,
Gordon.
 
GordonW said:
Not with these output transformers. Mine use the heavier outputs, found in the AMP101/AMP128/AMP132/AMP142/AMP150/AMP179 amps (the PPP 6V6), which are fine with a pair of 6L6s (one pair of 6L6s can provide about the same power output as a quad of 6V6s).

The AMP175/AMP185/AMP164/AMP169 outputs can actually be saturated in the bass, with an optimized single pair of 6V6s. There's no real reason to use 6L6s- these transformers will just saturate at an even higher frequency, as you force more power out of them...

Regards,
Gordon.
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s

Gordon,

That’s some good info you have there. Know I know what amps to look for in the future.
Here’s a question you might have an answer too. What about swapping out the output transformers for organ iron? I’ve come across some pretty nice size organ iron in the past.

Keith
 
The phono only, 185 models, have a single 6.3V filament winding that is rated for 2.7A of use. With 6L6 tubes installed you would be pushing 4.2A. Not saying it can't be done but certainly the limits of that winding are being stretched.
 
Kidmoe said:
The phono only, 185 models, have a single 6.3V filament winding that is rated for 2.7A of use. With 6L6 tubes installed you would be pushing 4.2A. Not saying it can't be done but certainly the limits of that winding are being stretched.
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Yep. The 175s have a second heater winding, that will also handle about 2.5 amps. With those, you can split the amp into channels- run all the heaters for one channel to one heater winding, and the heaters for the other channel to the other heater winding, and it will work with 6L6s.

At that time, you could then swap in some heavier output transformers, rework the driver stage and feedback loop to work with the 6L6s and new transformers, and it should work. But, it's not a drop-in, since the new transformers will need different feedback compensation than the originals...

Regards,
Gordon.
 
baddog07 said:
Would bigger 6v6 output transformers help with the bass saturation?
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Yes. Something like the Dynaco Z565 output transformers (as Dave G. mentioned in his articles about upgrading the Magnavox 6V6 amps) will improve the bass response markedly. You will want to stick with pentode mode (capping off and not using the UL taps on the transformers), unless you're willing to mod the phase inverter, as Dave describes...

Regards,
Gordon.
 
GordonW said:
Yes. Something like the Dynaco Z565 output transformers (as Dave G. mentioned in his articles about upgrading the Magnavox 6V6 amps) will improve the bass response markedly. You will want to stick with pentode mode (capping off and not using the UL taps on the transformers), unless you're willing to mod the phase inverter, as Dave describes...

Regards,
Gordon.
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Thanks for all the help....will check out Dave’s post again.
 
Good output iron is rarely cheap unless you get lucky. Sometimes you can salvage decent stuff from junk chassis though.

Unfortunately not all transformers are created equal, and to use one with a feedback amp usually wants some tinkering to make it behave. I have something I built from Hammond tone cabinet transformers, and it wanted a lot of fiddling to make it stable. They're just not hifi transformers, but I bet they'd be great in a guitar amp.
 
Your best bang for the buck with that 185, assuming its rebuilt to stock specs, would be listening to it thru its stock speaker system... The speaker cabs that came with mine have 15" woofers, so the bass doesn't really suck!!! Mids and highs are really good... I recapped them also...
There has to be a reason they are so popular 60 years later!!!!!
 
gadget73 said:
Good output iron is rarely cheap unless you get lucky. Sometimes you can salvage decent stuff from junk chassis though.

Unfortunately not all transformers are created equal, and to use one with a feedback amp usually wants some tinkering to make it behave. I have something I built from Hammond tone cabinet transformers, and it wanted a lot of fiddling to make it stable. They're just not hifi transformers, but I bet they'd be great in a guitar amp.
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Sounds like a pain in the butt to try and get it to work with organ transformers.
I’ve built a few guitar amps and you can get good tone from the organ output transformers but they won’t sound like the original design if that’s what someone is trying to achieve. The nice thing about tube guitar amp stuff is that there are plenty of new production parts out there at reasonable prices. In grasp of the average joe like myself.
 
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knockbill said:
Your best bang for the buck with that 185, assuming its rebuilt to stock specs, would be listening to it thru its stock speaker system... The speaker cabs that came with mine have 15" woofers, so the bass doesn't really suck!!! Mids and highs are really good... I recapped them also...
There has to be a reason they are so popular 60 years later!!!!!
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The cabs are long gone but I did keep some of the parts.
 
baddog07 said:
Here’s a question. Shouldn’t the screen voltage be lower than the plate voltage on the 6v6 tubes?
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Not when it's running the stock OPTSs into the stock 3.2 ohm load. The high screen voltage (which is completely safe on 6V6s) decreases the output impedance of the tube, making it work better into that load.

Regards,
Gordon.
 
I’m running my amp into an 8 ohm load. Does this change things or should I leave it alone?



GordonW said:
Not when it's running the stock OPTSs into the stock 3.2 ohm load. The high screen voltage (which is completely safe on 6V6s) decreases the output impedance of the tube, making it work better into that load.

Regards,
Gordon.
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