[o7brother]

But I have no experience with electrostatic headphones, so I wonder what influence an amplifier can have in this case

If you stick with the good amps (323, 353X, 717, and the mafia ones) you'll find the main difference is power output and not sound quality. I've written about this previously in the thread, but the going beyond a 353X is an exercise in severe diminishing returns.

 

[BowWazoo]

Ok, thx.
I think that I definitely don't need more power for the 507

 

[Tugbars]

There was a conversation about this recently, so I'll explain it very simply: It's easy for electrostatic amplifiers to multiply voltages. Koss amp has insane voltage swing for example(2400Volts peak to peak if i remember right), however, it delivers about 20 times less current than it can satisfy 2400vpss with full extension. What hard for electrostatic amps is to deliver enough current for full treble extension. Of course the equation of what makes an estats amp good isn't this simple: Higher current != better amp.There are more things involved in designing amps that can change the sound.

SR 507 is easy to drive, I don't expect a huge difference between 252S and 323 when paired with SR507. I have KGSSHV Carbon, SRM252 and SR507. I'll try both tonight with my SR507's and write what I hear here.

 

[BowWazoo]

Mr. Rauenbühler is sending me a Sirrah to test today, I'm curious.

 

[playmusic]

There was a conversation about this recently

Hello @Tugbars. I guess you are referring to @T3RIAD's posting

The main disadvantage I've heard is that Stax amps are current limited. For e-stat headphones, the higher frequencies require more current to drive than the lower frequencies.

Stax seems to indirectly confirm this for their older amps by a statement about the new SRM-700s:
"The output of J-FET excellent in low-noise amplification as well as large current emitter follower circuit brings out the full performance of earspeakers. Even the music source with much high-frequency ingredients can easily be driven. "

Could someone please explain the physics behind the difficulty to drive e-stat headphones at higher frequencies?
(As I understand it, the difficulty to drive some loudspeakers lies in the very low impedance of some loudspeakers at certain frequency ranges.
Is this similar with e-stat headphones, i.e. do e-stats have low impedances at higher frequencies?)

 

[padam]

Hello @Tugbars. I guess you are referring to @T3RIAD's posting


Stax seems to indirectly confirm this for their older amps by a statement about the new SRM-700s:
"The output of J-FET excellent in low-noise amplification as well as large current emitter follower circuit brings out the full performance of earspeakers. Even the music source with much high-frequency ingredients can easily be driven. "

Could someone please explain the physics behind the difficulty to drive e-stat headphones at higher frequencies?
(As I understand it, the difficulty to drive some loudspeakers lies in the very low impedance of some loudspeakers at certain frequency ranges.
Is this similar with e-stat headphones, i.e. do e-stats have low impedances at higher frequencies?)

Copied from another forum, but from a forum member:

"Stax amps are "mediocre" because they have to be mass produced and therefore at least be somewhat cost effective, Stax also almost never update their amp designs. Their tube amps are still stuck in the 90's, with plate resistor loading that burns up a large amount of the current the amp can supply (note that they know they don't have to do this, because their SS amps don't). They use unregulated power supplies that are just not fit for the task of consistently delivering on transient peaks.

Electrostatic headphones are a unique load because they are capacitive devices. Delivering a practically perfect 1V square wave into a normal dynamic headphone from 20-20KHz is quite frankly trivial in comparison to delivering a 100V square wave, especially at higher frequencies. The Stax are an incredibly difficult load to power, because the load impedance is unreasonably difficult to deliver power to at the extremes. A little thing that can be interesting is to check is Bob Katz measurements of the KGSSHV Carbon doing square waves at different frequencies, you can clearly see that the higher you go in frequency the harder it is for the amp to deliver a perfect or close to perfect wave. Note that this was a somewhat crude testing setup (not a capacitive load), but it works for simply being illustrative.

Now, if the KGSSHV Carbon, which is an extremely competent amp still has struggles with the load presented by the Stax headphones, then what about the much smaller and simpler Stax amplifiers which do not even have a regulated power supply? I think you can see where I'm going with this. From a purely theoretical standpoint designing an "overkill" aftermarket electrostatic amplifier makes a ton of sense. Even if it's only because Stax themselves won't (or can't) do it.

Basically Gilmore amps are closer to theoretical perfection because they are:

-Not current limited, unlike Stax amps (with a few exceptions for both).
-Use regulated power supplies, which again helps with delivering power into difficult loads at transient peaks and the like.
-Designed with better output stages (global feedback, no plate resistor loading etc.)

Whether you believe this makes an audible difference or not is up to you. But it is harder to design a well measuring amplifier which needs to put out power in the hundreds of volts rather than tens, at most. You can also see this if you compare a headphone amplifier with a speaker amplifier, the headphone amp is almost always less noisy, has less distortion and so on. Because it is easier to design something transparent at low power. You can compare some of the best measuring headamps on ASR to some of the best measuring speaker amps to see what I'm getting at."

 

[T3RIAD]

Could someone please explain the physics behind the difficulty to drive e-stat headphones at higher frequencies?

E-stat headphones and speakers are capacitive loads, which means their impedance decreases as frequency increases. Imagine there is a positive charge on one stator, and a negative charge on the other during the positive peak of a sine wave. Now, in order to reproduce the full swing of the wave, that charge has to reverse by the time you get to the negative peak.

For high frequencies, this swapping back and forth of charge happens really quickly, which means it requires more current to move the charge fast enough. Stax amps apparently can't manage a full +/- swing above 10 kHz when the amplitude is high. At least, that's how Kevin Gilmore explained it.

When people say their third-party amp improved the bass response, I don't believe it because bass frequencies are easiest to reproduce on e-stats. But if they say it improved the top end at high volumes, then that's plausible.

 

[armani006]

Mr. Rauenbühler is sending me a Sirrah to test today, I'm curious

Version 3.0 ?

 

[BowWazoo]

Yes

 

[Tugbars]

Answer to playmusic's question:
(disclaimer: if somebody knows better than me, feel free to bash me.)

Simply put, in higher frequencies, the amp has much less time to fill the stators with enough statical charge.(the louder you listen the harder it gets) at 20hz, it has 1/20 second to fill the stators with statical charge but at 20khz, it has only 1/20.000 seconds to do that(things are not that simple of course) So the current must be high enough to deliver enough charges in time. If it can't, the voltage sags. As the voltage sags, the signal integrity starts failing.

 

[Tarttett]

Does such a board exist in any form for the T1 series?

@Firschi has developed CCS modules for the various series of the SRM-T1.

 

[BowWazoo]

I borrowed the Sirrah, not because I was dissatisfied with the 252s, but out of curiosity to see if I could hear a difference between it and another amp.

To be honest, I started the comparison, biased:
"very probably you won't hear any difference," I said to myself
But it turned out differently.

After listening to EDM, jazz and rock for a few hours, I increasingly had the impression that the Sirrah was more precise, especially in the high frequencies.
Surprisingly, I also had a similar impression in the Bass. There is definitely more "Controll".
Also the Music seemed even more "coherent" with the Sirrah.

Especially in the high frequencies, the 252s often seems "clumsy" or "immature"
At least in direct comparison to the Sirrah.

It is somewhat contradictory
because the Sirrah is more present in the treble, and more detailed and at the same time less aggressive.

Anyway, the Sirrah replaces the 252s.

 

[armani006]

Yes

waiting for your feedback..

 

[BowWazoo]

Give me one sec.
Can't stop now...

 

[vitop]

Hello
I hope someone can help. I was reading the STAX II thread and it had some instructions and photos for converting a 100V SRM717 to a 117V unit. I opened it up and I think even though it is marked as 100V in the back, that someone has already converted it.

Can someone comment on these photos? I think it is already set up but I don't want to plug it in until I know for sure. The board looks good, but am I supposed to move any other wires or check other wires? I didn't follow that part all too well and I am going to go back and try and re-read it. Also, am I supposed to change out the fuse? What should the value be for 117V usage?

Thanks!