ESL amplifiers

[Prune]

I'm trying to find amplifier designs for driving electrostatic speakers directly, without having to use transformers on the output to bring up the voltage. It's been done for electrostatic headphones, so even though you need even higher voltage here, it should be possible.

 

[peterr]

i just posted this in the tubes section: from glass to mylar Of course it still has a transformer like all (except OTL's) valve amps do so I call it semi-directdrive

 

[SY]

There have been a few published designs- Hermeyer's in Audio Amateur comes to mind.

I've got one in prototype form, but the "real" unit build and documentation is awaiting more spending money.

 

[fdegrove]

Hi,

There's also Ultranalog's design:

PHILYRA

Click "Projects", amplifiers.

Cheers,

 

[MarcelvdG]

I recently designed and built a simple high voltage amplifier for the do-it-yourself electrostatic loudspeakers my colleague Frank Verwaal is building. I've so far only looked at step and sine responses and got the frequency compensation right. It will take at least several weeks, probably longer, before we can actually try it on Frank's loudspeakers.

I intend to write a design report and send it to an audio web site, but if you want a sneak preview of the schematic, I can send it to you by e-mail once I got it scanned in.

 

[SY]

Marcel, I'd love to see it. I'll post mine as soon as I can get my $#@!ing scanner to work properly.

 

[Prune]

I was looking for a design with balanced input, and Ultranalog's is not.

 

[MarcelvdG]

SY and anyone else interested in receiving two pdf files with my amplifier schematics, could you send me an e-mail?

 

[jackinnj]

if you look in "The Art of Electronics" -- the section on power supplies deals with a high voltage regulator using a pair of MOSFETs -- the particular FET unit is no longer made by Motorola, but there are now plenty of husky devices from IRF and Fairchild to choose from and the idea is the same -- the gate of the first MOSFET can be fed by a sine or music source instead of a voltage reference -- this regulator circuit is really an amplifier and, according to the author, quite good driving reactive loads.

i have built a couple versions of the regulator and used it in a microprocessor controlled high voltage supply -- to test it I used a step generator and a ramp generator -- it is very easy to implement.

and mercury vapor rectifiers in audio equipment are a silly idea. They are just glowing noise generators.

 

[Bas Horneman]

a little smalltalk..not trying to argue...since I have never used any..

"and mercury vapor rectifiers in audio equipment are a silly idea. They are just glowing noise generators."

They must be doing something well because people are saying they are the best thing since sliced toast????

 

[jackinnj]

ever heard of the term "regulator hash", or "rectifier hash" -- the Hg rectifier tubes are prone to generating high frequency noise, they are also prone to flashback and peak current limitations...and if you drop one don't vacuum up the little bits unless you have a HEPA filter on the vac -- elsewise you will wind up aspirating mercury vapors and wind up "mad as a hatter".

 

[MarcelvdG]

Yesterday my colleague Frank Verwaal finally tried my high-voltage amplifier with one of his loudspeakers.

Unfortunately, he found that he needs more than the 2kV peak which the amplifier produces for the sound levels he normally listens to.

For what it's worth, he liked the sound very much, particularly the high frequencies. He has the subjective impression that he heard more treble with the amplifier than with a transformer, but also that the sound is much cleaner, with less intermodulation between bass and treble.