Electrostatic amp suggestions under $1500? GES the only choice?

[hozo]

Looking to get back into some electrostatic headphone DIYing.  Is WooAudio GES pretty much the only production amp under $1.5k that's not from stax?  I see KGSS and BH are even more expensive than before.  And of course there are some super special edition amps that are just way out of my range.  Any suggestions welcome.
 
ps. diy eXStatA is a bit too much for my basic electronic skills

 

[Lil' Knight]

I heard that a commercial version of the eXStatA will be announced at CJ. You might want to wait until there to see if it's true.

 

[tintin47]

Also, you can always commission a build of the exstata.  It would come in far below $1500 even with every bell and whistle you can think of.

 

[spritzer]

Your best bet would be to get a used Stax SRM-717, in terms of value it can't be beat.  Due to high demand they can be hard to find but then there is always the Stax SRM-727.  It isn't as good as the KGSS/717 (a bit too colored for my liking) but it has more power then an Exstata, more voltage swing and a lot less THD (total harmonic distortion).  It's also easy enough to change from 100V over to 117V if you can do some basic soldering. 

 

[hozo]

Quote:

"it has more power then an Exstata, more voltage swing and a lot less THD (total harmonic distortion). "

Hmm,  didn't realize the exstata had less voltage swing.  That might not work.  Last time I used a KGSS, and my stats weren't exactly super sensitive.

 

[spritzer]

The Exstata has a +/-300V supply but the Stax amps all have +/-350V plus the output stage has more power. 
 
What D/S (diaphragmstator) gap were you using for you 'stats?  The bias might simply have been too low for the gap. 

 

[hozo]

Ah, +/-300V.  That should be plenty.  My wild guess is it was 5-8dB less sensitive than the Omega 2.   My spacers varied from 0.25-2 mm.  Bias varied from 500-3000V.  With the KGSS at 580V bias, the SPL was plenty loud at 1 o'clock.  However, there was a high pitched buzzing sound that I never solved.  I thought it was arcing somewhere, but never could isolate it.
 
Looking back, what I thought was stator-to-diaphragm arcing was probably charge migration on the diaphragm?  I used graphite and probably didn't have a consistent coating.  Going to try some anti-static sprays this time around...

 

[spritzer]

I'd go for much higher then +/-300V for something that inefficient.  We are working on a +/-500V version of the KGSS but it will be DIY only.  Should obliterate all of the tube amps though with nearly 2kV P-P...
 
Graphite is a horrible choice for long term stability or if you want to have any control over the actual resistance of the coating.  If the resistance would be too low then you will get a lot of odd issues and increased distortion to go with it. 

 

[hozo]

Quote:

... If the resistance would be too low then you will get a lot of odd issues and increased distortion to go with it. 

Definitely, I tried a low resistance coating one time (almost silver from graphite) and it did a continuous series of "buzzzzzzzZZZ POP."  Do you have any specific recommendations for coatings that worked for you?  I've seen the glue recipes but they're more for ESLs.  Seems like it would add too much weight when using 1.5 micron Mylar. I saw some anti-static sprays, but haven't tried any of them yet (most are special order).

 

[spritzer]

I've tried most of the available Quad ESL coatings (non nylon) and they all worked pretty well when airbrushed onto the diaphragm.  There is also a mixture of glue and ink which I've been meaning to try but I need some old driver to rebuild to get a good baseline for the comparisons. 

 

[hozo]

Quote:

I've tried most of the available Quad ESL coatings (non nylon) and they all worked pretty well when airbrushed onto the diaphragm.

 
oops, just saw this..
 
Spritzer, care to share which one worked the best or easiest to obtain?  I also saw that PVA + ink formula by chinsettawong.  He seems pretty confident in it, and built full ESLs with it.  I'll have to give it a try too.  Have you tried Licron Crystal for your headphones?
 

 

[spritzer]

This was all years ago so it's burried in a haze but if I were to do this all again (which I probably will) then I'll have some custom formula made.  The ER audio solution was easy to work with which is just about all I can remember from that period...

 

 

[pabbi1]

There are other opinions, specifically that I like the eXStatA better than any Stax amp. Period. Better than the KGSS, better than Woo (an old KG design), and better than my departed BH.
 
There are some strong biases against the eXStatA, especially by those who have never heard it.
 
Oh, and anyone can build an eXStatA with basic skills - not so true for other designs, speaking from experience. And, we'll see about actual specs at CanJam.

 

[spritzer]

I take it this was meant for me and I've had my Exstata up and running for a week now (+/-350V, Toshiba transistors and a KGSS PSU since the stock unit is a joke) and it isn't even close to the KGSS, far less linear.  Just look at the measurements for it, THD is way up. 
 
A BH is hard to build correctly and unless you know what you are doing, it will blow up.  Simple as that.  The KGSS OTOH is dead easy to build, just populate the boards and it works.  Same will be true for the KGSSHV. 
 
[mod edit]personal attack removed

 

[pabbi1]

Yes, I use 2sc3676 as well, and don't find the psu lacking at all.
 
Glad electrostat users listen to graphs, but, IME, the KGSS just doesn't sound as good as eXStatA, and 60 eXStatA users seem pretty happy with their units.
 
Anyone able to make CJ will be able to hear no less than 3 eXStatA, to see for themselves.
 
Guess I missed this vapor product, KGSSHV - has it been published, or just talk? Using the same old parts? Same old design, with a few moar volts? Maybe it's time for a little peer review.