[spritzer]

The gain is 500 I believe or I'm just too fried from reading way too many tube data sheets today.

 

[Beefy]

No, I'm quite sure it is ~1000

Quote:

A small amount of NFB is applied to the sources of the diff pair. However, the NFB is small enough that it does not entirely control the gain of the amp, which is still primarily in hands of the jfets. The values chosen are an average value to bring the average gain down to about 1000. Jfets with high transconductance will cause the amp to have higher gain and vice versa.

From The eXStatA Electrostatic Amplifier

 

[spritzer]

Ahh ok. I blame it on obscure TV tubes messing with my brain...

 

[BoilermakerFan]

Quote:

Originally Posted by spritzer /img/forum/go_quote.gif Ahh ok. I blame it on obscure TV tubes messing with my brain...

Oooo. I have a box of those and HAM radio tubes in my basement. Send me a PM if you come across some with great potential.

 

[runeight]

Well, it depends on how you measure gain, but ...

If you put 600mV peak to peak across the balanced inputs you will get, approximately, 600V peak to peak at the output. Approximately because it depends on the transconductance of the jfets as you all know.

But, with sources that routinely generate 2V or more any one of them can drive this amp to clipping.

 

[spritzer]

Quote:

Originally Posted by BoilermakerFan /img/forum/go_quote.gif Oooo. I have a box of those and HAM radio tubes in my basement. Send me a PM if you come across some with great potential.

There are some strong candidates but nothing solid until I've built and tested a prototype.

 

[sumo-kun]

Regarding balanced vs SE, how about if I want say 600V at the output. For SE, that means the volume pot will need to be turned to say position X. But for balanced, the pot will be turned to half of X, or basically the amp will need to amplify half as much? So keeping that in mind, won't distortions etc from the higher gain needed in SE affect sound? Whether you'll be able to hear the difference or not is another matter, I know

Just thought I'd throw that on the fire

 

[runeight]

Yes. I explained this in post a few pages back.

The distortion goes up slightly if you drive the same output with SE.

 

[jgazal]

Quote:

Originally Posted by sumo-kun /img/forum/go_quote.gif Regarding balanced vs SE, how about if I want say 600V at the output. For SE, that means the volume pot will need to be turned to say position X. But for balanced, the pot will be turned to half of X, or basically the amp will need to amplify half as much? So keeping that in mind, won't distortions etc from the higher gain needed in SE affect sound? Whether you'll be able to hear the difference or not is another matter, I know Just thought I'd throw that on the fire

Quote:

Originally Posted by runeight /img/forum/go_quote.gif Yes. I explained this in post a few pages back. The distortion goes up slightly if you drive the same output with SE.

Wouldn't be better to add a "phase splitter"?

A single ended phase signal enters the splitter and two signals, on in phase and the other out of phase sinal come out the splitter.

Does this increase single ended level and maintain volume pot at the same balanced position?

Best regards,

Jose Luis

ps.: sorry, Alex already answered at post 617: http://www.head-fi.org/forums/6130256-post617.html

 

[HeadphoneAddict]

Quote:

Originally Posted by wiatrob /img/forum/go_quote.gif Balanced vs. Un - that's another thread isn't it? That said - we did notice a difference with the proto at RMAF. even though there's not supposed to be a gain difference between the two inputs, we heard lower gain on the SE. Larry, did we ever listen to the dif's after we solved the source problem? I think it was only running balanced from my Opus the rest of the show. Sherwood has listened extensively SE, perhaps he could be cajoled into sharing his experience. I can A/B with my DAC Magic, but can't be sure of it's output stage topology differences between SE and Balanced.

The "dif's" ?

 

[wiatrob]

Quote:

Originally Posted by HeadphoneAddict /img/forum/go_quote.gif The "dif's" ?

That's what we computer geeks call a 'difference'

Quote:

Originally Posted by jgazal /img/forum/go_quote.gif Wouldn't be better to add a "phase splitter"?

And I think the addition of a phase splitter (while an excellent solution) would be beyond the scope of the requirements for this particular amp.

Luckily it's got spectacular price/performance.

 

[pabbi1]

Ok, ok, ok so I have a reading comprehension problem - completely missed the 51k load resistor - but (as luck would have it) I do have a 50k 5w - will that work, or do I need to cobble 2 extra 500r (10w-20w, iirc) resistors also (again, what I happen to have)?

Always something.

Oh, and if anyone is Jonesing to do a phase splitter, I have some interstage transformers that might interest you.

 

[runeight]

50k 5W is ok.

 

[HeadphoneAddict]

Quote:

Originally Posted by wiatrob /img/forum/go_quote.gif That's what we computer geeks call a 'difference' And I think the addition of a phase splitter (while an excellent solution) would be beyond the scope of the requirements for this particular amp. Luckily it's got spectacular price/performance.

I don't recall how the RCA inputs sounded vs the XLR, if that's what you mean. I do recall that the 5v from the stock PS Audio DLIII XLR was a bit too hot for the inputs, while the modded PS Audio XLR and Opus DAC were better.

 

[Emooze]

Hooked up my amp to the power supply finally. Everything is looking good. Going to check the offsets in a bit and then its listening time!

Running at stats at a lower voltage should still work, correct? I never got around to rechecking the bias voltages and its way to wet and nasty out to go to the lab.