Re: SET amps -- a very special hedonistic niche within a niche

"Bob H." <bobhedberg@xxxxxxxxxxxxx> wrote in news:1154195378.592215.208750
@i3g2000cwc.googlegroups.com:

I'm not sure how much UV would be generated by the tiny plasma used in
audio. Our instruments had a plasma about 3/4 inch thick and about 1.5

Tiny? It's about 800-900 W per channel in my design (about twice that of
the Plasmatronic speakers, so I can get lower crossover frequency). Plasma
thickness needs to be below wavelength of the highest frequency to be
reproduced, so about half a centimeter. Height in my case will end up 2-
2.5 cm in each channel (with my configuration and full PSU power in one set
of electrodes I can get a 5 cm discharge). To avoid the need for special
gas, I'm using microhollow cathode discharges as the electron source to
drive the main discharge, rather than simple cathodes with their associated
cathode fall instabilities leading to glow-to-arc transitions. My initial
copper/mica MHCD sandwitches eroded very quickly, so I've machined some
from tungsten which I platinum-plated myself) and sapphire wafer that I got
as free sample (cutting and drilling sapphire is a bitch!). Platinum wire
dissolves easily in an electrolytic cell with HCl (muriatic acid for the
Amerikhans among us) forming chloroplatinic acid which is used for plating;
alternatively, Aqua Regia will work if, after dissolving the platinum, one
repeatedly evaporates the nitric acid from it(the nitric has a higher
evaporation rate) and replenishes with HCl until there's no significant
nitric remaining. For proper plating some lead salt also needs to be
present; I made some lead acetate (through the copper sulfate->copper
acetate->lead acetate method) and used that. The tungsten electrodes that
are plated need to be baked in intert atmosphere at very high temperature
to diffuse the platinum into the tungsten surface, otherwise it comes off
easily; I had someone do that for me as I don't have a vacuum furnace; this
procedure is described in a patent which I can't cite at the moment as I'm
not seeing it in the usual folder and too lazy to look it up again.
The MHCD upper electrodes are biased with a resistor from the main
discharge anode. I'm not sure how the MHCD sandwitch's capacitance will
affect audio modulation of the signal; I've only done DC plasma this far
(used salt water resistor as ballast; I've yet to build the amplifier).
.

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