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Posts by kevin gilmore

I know a person that did this for years and years with a pair of Phillips davids.   you just need a good inverter, something real, not one of the low power toys. something in the 300 to 400 watt range.
latest versions of the susy dynalo and susy dynahi are current production parts with pzta series surface mount parts. parts should be available for at least 5 years.   probably much more because the mpsa versions are already 30 years old and the surface mount versions are the same silicon.   I also have a current feedback amp that's in between the two as far as power, also current parts and easy to build.
for the price it had better be better.
I was referring to the universal nature of the amplifier. not the amplifier itself. You will never see a company like viva do a universal amplifier.Of this I am sure.  But they could do an electrostatic amp with 8 x 845 power tubes.That would be wonderful. major edit, its 8 power tubes, not 4. same as megatron.
 back to that crap again. Viva only does dynamic headphones. That means you will never buy it.
but an all tubes direct coupled output electrostatic amplifier already exists. (one really good cap between the driver and the outputs) its called the megatron. No input transformers. No output transformers. your choice of 1600vppss or 2000vppss depending on the size of the power supply. and for the very few who are capable, an all DHT fully direct coupled version. (its a bit pricey)
I would send them the spies-hecker or 3M-imron from my personal stash.   Real Ferrari paint is very hard to get unless you know someone.
The difference will be between 2000 hours and 10000 hours. With the prices of good versions of those tubes, it can make a difference.   Yes they get hot. REAL hot.  10 volts at 3.25 amps. So 32 watts just for the filament per tube. Plus 20 to 25 watts for the plate.   these tubes with the amorphous transformers is a great way to do things.   But it really needs to be painted ferarri red.
in the higher power DHT tubes, DC ends up taking many hours off the life of the filament due to hotspotting.  And 60hz AC supplies no matter how hard you try always have a slight bit of hum.  So pure sinewave drive at 40khz is much better. Also much more complicated.
the viva is a 15 watt amp, so the distortion is probably close to 5% with no feedback. The 845 is a class A Modulator/amplifier, and actually works at lower distortion at much higher power levels with much higher plate voltages. Can actually get down to 1% at 50 watts.   Here are a few more entertaining numbers, asked by a person on an island off the coast of spain.   Singlepower MPX3 with 6sn7 tubes...  Actual measured distortion 5.4% into 300 ohms at 2 volts...
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