eXStata DIY Electrostatic Amp for Intermediate DIYers

[ericj]

Quote:

Originally Posted by spritzer /img/forum/go_quote.gif You can also just setup the HB supply for a given value and then use a high impedance voltage divider to get any voltage you'd like. It's just 3 resistors so very easy.

There are indeed any number of ways to skin that cat, and yeah, tacking on another voltage divider is one of them.

In the basic configuration you have one bias voltage under about 360v and another bias voltage over about 360v.

So if you just have regular and pro bias stax, set the low one to 230 and the high one to 580 and you're set.

If you had low and high bias stax and an esp950, just use 580 for the esp950 too. Or maybe set it for 590. This isn't many volts difference so it's perfectly ok to just be in the ballpark. I doubt many commercial amps are right on the nose of their stated bias voltage anyway.

It's the guy who wants to drive his ET1000, normal bias stax, HE90, and pro bias stax all at their factory specified bias voltages who has to get creative.

Edit: I really should staxify my Stagnavox this weekend and try it out on the eXStata. Those are, what, 200v originally?

 

[smeggy]

I have the normal and pro stax, ESP-9 and 950 and ET1000 so it'll be a juggling act, need one of those relay boards to set output voltages for me.

 

[ericj]

Well, one option is to determine the difference in the trimpot setting between 400v and 580v on the high side, and then calculate the value of the resistor string you'd have to parallel with the trimpot to allow you to switch back and forth between 400v and 580v.

Or if you can find a panel-mount volt meter with a high enough impedance that it won't drag down the bias circuit, use a panel-mounted pot instead of the adjustment trimmer and just adjust the bias on the fly for whichever headphone you're listening to.

We've had some difficulty finding panel meters with a high enough input impedance for that, though.

I suppose you could pull a SinglePower hack and just gut a cheap DMM.

 

[insyte]

Quick question, is the exstata designed to take in single ended or balanced inputs?

 

[srserl]

Quote:

Originally Posted by sachu /img/forum/go_quote.gif I will be in SFO this weekend...I can haul the sand version with me along with my Koss ESP950 if someone wants to listen to it. Just give me a heads up..if no interest then I won't take the trouble.

If you are up for it, I would love to meet and listen. It's a bit of a drive, but it might be fun since I didn't get to attend either can jam or the norcal meet. Nor have I ever met you. This will probably be my next hp amp I will build, and maybe you can talk me into building an ehha as well

Hmmm, I seem to remember someone warning me about this site and my wallet or some such.

Scott

 

[HeadphoneAddict]

Quote:

Originally Posted by insyte /img/forum/go_quote.gif Quick question, is the exstata designed to take in single ended or balanced inputs?

Wiatrob's will take both, via input switch on the back.

 

[ericj]

Quote:

Originally Posted by insyte /img/forum/go_quote.gif Quick question, is the exstata designed to take in single ended or balanced inputs?

Yes.

If you have balanced input, it takes it. If you only have single-ended sources, you ground the negative input on each amp board.

The only difference this should make is 3db less gain in the single-ended configuration - which isn't a problem unless you have a really quiet source.

 

[sachu]

Quote:

Originally Posted by srserl /img/forum/go_quote.gif If you are up for it, I would love to meet and listen. It's a bit of a drive, but it might be fun since I didn't get to attend either can jam or the norcal meet. Nor have I ever met you. This will probably be my next hp amp I will build, and maybe you can talk me into building an ehha as well Hmmm, I seem to remember someone warning me about this site and my wallet or some such. Scott

Sounds good..shoot me a PM and we'll take it from there.

Oh and yeah...build the EHHA first!

Hope that is indicative enough of how highly I think of that amp.

By then the details of this amp would've been finalised am thinking.

Edit:

I'll see if I can haul the EHHA with me as well...

 

[les_garten]

Quote:

Originally Posted by sachu /img/forum/go_quote.gif Sounds good..shoot me a PM and we'll take it from there. Oh and yeah...build the EHHA first! Hope that is indicative enough of how highly I think of that amp. By then the details of this amp would've been finalised am thinking.

I had not looked at Alex's amps until this came along. So in looking here I went to Cavalli, the web site, and was interested in the EHHA as an alternative to a B22 build. Both look like awesome amps. How would you compare and contrast the EHHA and B22? What will the EHHA II be? Not much on the site about it.

 

[sachu]

Quote:

Originally Posted by les_garten /img/forum/go_quote.gif How would you compare and contrast the EHHA and B22? What will the EHHA II be? Not much on the site about it.

The B22 and EHHA are both in my opinion reference quality DIY amplifiers.

The B22 is the best Solid State amplifier I have heard thus far. To my tastes the EHHA sounds better all around.

The main area where the EHHA trumps the B22 again IMO is that it costs almost half as much to build (a no frills build) while still equaling or eclipsing the B22 in performance, both power and sound quality wise.

Keep in mind the EHHA has been around for over 2 years..just hasn't had any exposure till early this year.

I mean if I had my amp cased up completely I wouldn't mind sending it on a loaner program cause this amp deserves to be heard.

The EHHA 2..well ;lets not go there....maybe Alex will get on it after the stat amp is up and running full steam..we can pick his brain about the EHHA 2 after that. AFAIK, the design is for the most part reaedy to go into prototyping phase. But it is a speaker amplifier the likes of the B24. Probably not as high powered as the B24.

I don't want to derail this thread..we can move this over to the EHHA thread from here on.

 

[les_garten]

Quote:

Originally Posted by sachu /img/forum/go_quote.gif The B22 and EHHA are both in my opinion reference quality DIY amplifiers. The B22 is the best Solid State amplifier I have heard thus far. To my tastes the EHHA sounds better all around. The main area where the EHHA trumps the B22 again IMO is that it costs almost half as much to build (a no frills build) while still equaling or eclipsing the B22 in performance, both power and sound quality wise. Keep in mind the EHHA has been around for over 2 years..just hasn't had any exposure till early this year. I mean if I had my amp cased up completely I wouldn't mind sending it on a loaner program cause this amp deserves to be heard. The EHHA 2..well ;lets not go there....maybe Alex will get on it after the stat amp is up and running full steam..we can pick his brain about the EHHA 2 after that. AFAIK, the design is for the most part reaedy to go into prototyping phase. But it is a speaker amplifier the likes of the B24. Probably not as high powered as the B24. I don't want to derail this thread..we can move this over to the EHHA thread from here on.

Yeah Thanx! Things were a little slow and the EHHA was mentioned so I ust kinda blurted it out.

 

[awpagan]

It has been a while since i've been to Head-Fi.
I still have my old LV Stax.
Will have to keep an eye on this thread.

 

[runeight]

Well, nice to have you back. It has been quite a while. Hang on to your stats because we're almost there.

 

[runeight]

It appears the the hybrid proto builders are not moving along as fast as they had hoped. So, why not post the tube schematic while we're waiting.

The tube version is very nearly identical to the sand version. It fits on the same board size and uses the same PS and will be completely interchangeable with the sand version provding you have the heater supply. And, if you use the Hammond 270AX transformer its heater supply is exactly what you need.

Schematic. See below:

In this case the 6S4 does the high voltage duty that was performed by the KSC5042 in the sand version.

However, trodes are depletion devices not bjts and we can't make a wilson current mirror with them. So we revert to a standard two-device mirror using 150V transistors. The mirror now drives the cathode of the tube while the grid is grounded. Grounded grid circuits have been around since tubes. The Blue Hawaii uses a GG for its EL34s.

As before the gain of the amp is still in the hands of the jfets at the input.

Hopefully some of the slow-poke prototypers will have news soon.

Both boards will be available on the first round (assuming there are no problems with the tube version). Still working on the exact plan to ensure that everyone gets a solid build.

Stay tuned ...

 

[insyte]

Is the exstata going to be made available as kits?