SE Electrostat amps

As you mentioned, conventional electrostatic transducers (drivers) require that they be driven with a balanced/push-pull signal. You can see why in the DIY electrostatic headphone article on headwize. 

There are some unusual drivers that are designed differently to run on single ended signal: the stators are biased with DC, and the signal is sent to the membrane, exactly the opposite of how a conventional electrostaic driver works. There are also a few amplifiers that run all of the active stages single ended with a big fat transformer on the output to create the balanced signal. Neither one is what i would call "common" though.

Quote:

Originally Posted by inburrito 

Thanks for helping the newb.  Since electrostatic speakers don't quite work like this (and of course work just fine with SE amps; a signal is a signal) it was slightly perplexing.  But my guess was in the ballpark.

When you use an electrostatic speaker with a SE power amp there is usually a transformer between the amp and speaker which steps up the voltages, and converts the SE signal to balanced. 

All electrostatic transducers use some sort of a push pull arrangement otherwise the THD is quite high.  Ari is right too that all ESL's have internal transformers which work exactly as the small Stax SRD boxes. 

Hello to All !
This is my first post at Head-Fi. 

I recently got myself a Stax Lambda Nova Classic/SRD7mk2 and feeding this through my "EL84 (NOS Mullard) direct coupled to 2A3 (Emission Labs Mesh)" Amp (http://www.tubemaster.de/e-diy-EL842A3.html) and a modified Revox B226 CD player with tube out, so there is only one capacitor (V-Cap CuTF) in the direct signal path from the DAC to the full range speaker.
It is very exciting to listen to the headphones and the sound is very good and it is just about loud enough for me.

My question to all the experts here is:

To get the best sound out of the headphones, shall I build an amplifier (I like the diy Auridux ECC99 mu follower with ccs design) or use my speaker amp, switched to different (custom made?) SE to PP transformers?

I think stepping down the music signal by the OT and then stepping it up again by the SRD7 degrades the sound. Am I right here?

There is very little on the web about SE Amp driving electrostatic headphones and I don't know why, since I think, that if you split the signal at the beginning of an amp, the following stages will change the symmetry of the signal.

Hoping for some help and hints.
Torsten

I do think that using cheap, high ratio transformers like the ones in the SRD-7 will not do the sound any favors.  There is also the issue of the SRD-7's being designed in 1971 so they really aren't suitable for the modern models.  Even with very high quality transformers stepping the voltage down just to step it back up isn't really a good idea. 

Thank you spritzer, yes, that is my fear too.

Do you know if I could get good transformers for the 2A3?

I guess the valve could swing 100 V, so a 1:4 transformer would do.

Do they exist?

Can you tell me what sound to expect compared to a simpler diy electrostatic headphone amplifier like the tubecad, Stax SRX or Auridux?

I like the Blue Hawaii design, but unfortunately it is way out of my financial reach at the present moment.

A transformer like that would have to be custom made by somebody who knows what they are doing. 

The tubecad is about as simple as it gets.  Fit it with higher voltage tubes, higher rail voltages, regulated PSU and negative feedback and it isn't a bad beginners amp.  The SRX is one of the best amps you can build if done right.  Same deal as with the Tubecad, change the tubes, higher rail voltages etc. and it is very, very good.  You can see one I rebuilt in the thread in my signature. 

Thank's a lot, that for sure gives me some guidance. I also will have a look at your rebuilt.

The SRX schematic I like a lot and it's simple.

Thank you for the hints to improve it.

Any comments on the Auridux with mu follower ECC99? It's simple enough and got a constant current source, all it needs is a driver/input stage. 

Why is it that it's not popular as a diy stax amp, I hear very little....

Most people don't know about the Auridux and the instructions for it are a bit too complicated IMHO.  It's not a bad amp by any means though and the ECC99 is a lovely tube.  

Thank you very much for all your help, this is much appreciated.

I'll go to the drawing board now and see what comes up....