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Posts by kevin gilmore

not at all like the viva.   direct drive dc coupled. You would need 8 x 845! and some really large filament transformers.   I don't pay attention to how much these things cost. If I did, I would not be building them. Others that have built them might have a better idea.
Lets look at that Viva for a bit.   2 output tubes.   1 per channel.   By definition, its a single ended amplifier with the output transformer as the plate load for the tube. The transformer has to be gapped because it carries the DC current of the tube. This is a well known circuit, as old as old gets, and to many people, especially with efficient horn speakers probably as close to nirvana as one can get.   So whats the difference between an electrostatic...
although I would love a red one, everything else is black including the speakers which are also painted with automotive paint.
that is what I get for continuing to use an ipad   BUT  transformers are clearly a compromise and in some cases a really bad compromise.   a OTL electrostatic using 845's would not be a compromise.
 Speakers (8 ohms)ortho etc without a transformer.  eric you clearly do not understand. 845 may be a great and powerful tube, and wonderful for direct drive electrostatic,but it cannot drive low impedances without a transformer. with a special transformer, sure no problem. And closer to 60 watts. kgsshv-carbon actually tested today driving transformer in reverse.Good for about 9 watts into 50 ohms.
The original has hum issues due to the unregulated power supply. other than that, sound is absolutely identical. exactly the same partsincluding the xicon resistors. mine has a whole bunch more heatsink and a fully regulated power supply. megatron is an all tube monster, there are probably close to a dozen builtaround the world. I could do a megatron with 845'sit would weigh close to 350 lbs and consume at least 600 watts.
I see the 150k resistors, they are 1%, just like the previous pictures.   still local feedback loop
 This is something I have been working on very hard of late. The short answer is no. But it depends on how stuff is measured. I had an antique sound technology 100A.  Absolutely filled with opamps.  made thd measurements completely analogwith complex filters to remove the fundamental. Even though it could go down to .001%, it always generated muchhigher numbers than the digital things. A while back lots of people were measuring stuff with audio sound cards that were 16 bit...
the two phases may be significantly unbalanced.   previous measurements on that amp, and the phases already differ in amplitude by about 10%.   I would measure it.  signal generator set at 60 hz sine wave and rms voltmeter is all that is needed, but a scope is better.
the phase splitter on the m20 is very sensitive to tubes, and the second gain section heavily relys on Rp. So swapping a 12ax7 with a 5755 might cause issues. Best to measure with a scope and signal generator, or a rms reading voltmeter
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