Electrostatic Headphone Amplifier Review & Comparison

[Svperstar]

I almost bought the Koss ESP/95X at one point when it was on large discount due to closing of Drop's EU warehouse - I'm glad I didn't. Electrostatic headphones are still something I'd like to try in the future, but I don't think I'll be buying any blind.

3 year late reply but thats too bad, you should have picked one up. They sound great especially given the price.

 

[Svperstar]

The gain doesn't help if the amp starts to distort or completely runs out of current.

My Stax SRM-T1S just got here today. I still have the Stax 007 mk2 in the mail, the only electrostat I have here is the Koss 95X, luckily I bought a cable to let Stax amps run them. Holy crap the Stax amp has way more power. I barely have to go bettween 2-3 on the dial, my RME ADI-2 is at 0 / +7, connected via XLR.

No need to drive the gain higher. The Koss are getting plenty loud. We shall see when the actually Stax headphones get here.

 

[Svperstar]

Having compared one of the better Stax amps (SRM-717) and Carbon in a pretty flawed single-blind test... you can guess what I thought of the claims of increased soundstage, dynamics, black background, detail, etc.

What did you think? I currently own a 717, listening too it now, I was thinking of getting a Carbon or something else end game. Did the Carbon sound any better then the 717?

 

[milosz]

What did you think? I currently own a 717, listening too it now, I was thinking of getting a Carbon or something else end game. Did the Carbon sound any better then the 717?

What I've found is that the various Kevin Gilmore electrostatic amps I've tried allowed greater undistorted voltage swing. This was especially apparent on the SR-007a which seems to need more oomph than the other 'phones I've tried, but which also produces really great sound when driven well. I new have a Carbon, I used to have a KGSSHV - I did not hear much (if any) difference between them, but I had a good offer for the KGSSHV so I sold it and kept the Carbon. If you use any bass EQ at all - and I think some is needed- the Stax amps just seem to fold up. Also, their bias voltage is not well controlled, which leads to certain other problems. Only the unobtainium Stax T2 seemed to really check all the boxes, at least as far as I know after reading some analysis of it's circuitry.

• The SRM-T1 S had a maximum output voltage of 300V
• The SRM-007tA / SRM-007tII have a maximum output voltage of 340V
• The SRM-717 and SRM-727 have a maximum output voltage of 450V.
• The SRM-T2 had a maximum output voltage of 630V
• The Carbon has a voltage swing of 1440V
  

 

[Svperstar]

What I've found is that the various Kevin Gilmore electrostatic amps I've tried allowed greater undistorted voltage swing. This was especially apparent on the SR-007a which seems to need more oomph than the other 'phones I've tried, but which also produces really great sound when driven well. I new have a Carbon, I used to have a KGSSHV - I did not hear much (if any) difference between them, but I had a good offer for the KGSSHV so I sold it and kept the Carbon. If you use any bass EQ at all - and I think some is needed- the Stax amps just seem to fold up. Also, their bias voltage is not well controlled, which leads to certain other problems. Only the unobtainium Stax T2 seemed to really check all the boxes, at least as far as I know after reading some analysis of it's circuitry.

• The SRM-T1 S had a maximum output voltage of 300V
• The SRM-007tA / SRM-007tII have a maximum output voltage of 340V
• The SRM-717 and SRM-727 have a maximum output voltage of 450V.
• The SRM-T2 had a maximum output voltage of 630V
• The Carbon has a voltage swing of 1440V

Thanks for the post, but the "stator to stator" voltage swing and maximum output voltage listed by Stax aren't an apples to apples stat. I'm not an EE so don't ask me to explain exactly how they compare.

I use Equalizer APO with my 007 and CRBN and it doesn't distort but I'm curious how it would sound if I upgraded.

 

[esl 63]

Why is the input 2Volt when the spec of this device states 100mV?
Is anyone in here surprised that the unit is clipping?
The measurements is of no value at all. Really sad. Put so much effort and try to measure something and then mess everything up so badly and then publish it here?
Why?

 

[gvl]

The review concluded it wasn’t clipping, just inability to deliver power without distorting badly.

 

[esl 63]

I measured my SRM T1 (CCS modded by me) but still very similar construction with tubes and got my second harmonic at -90dB (dominant harmonic).
Is it possible that CCS can reduce distortion that much? I have not seen FFT on an original T1 unfortunately...

 

[Svperstar]

I decided to take the plunge and got an "end game" Stax amp, the Blue Hawaii. It uses the same tubes as the famous BHSE amp from HeadAmp.

One thing interesting I noticed right away is the "stax farts" noises that my various estats make when moving them around your head/breaking the seal sounds way different and way louder on the Blue Hawaii compared to my other estat amps.

It has a ridiculous amount of power on tap, part of me wants to pack it all up and send it to Amir to be measured. I wanted to measure it myself but the amp builder and even Kevin Gilmore himself told me to knock it off or I am going to blow up the amp or electrocute myself.

 

[solderdude]

Perhaps the current limit resistor in the bias voltage path is lower resistance or the bias voltage is a bit higher or the plate voltage is higher at the moment you break or make the seal ?

 

[BrooklynNick]

One thing interesting I noticed right away is the "stax farts" noises that my various estats make when moving them around your head/breaking the seal sounds way different and way louder on the Blue Hawaii compared to my other estat amps.

Volume matched with your other estat amps?

 

[Svperstar]

Volume matched with your other estat amps?

No, I noticed the second I put them on my head, basically my other 3 estat amps sounded the same. The BH was very different right away regardless of volume

 

[BrooklynNick]

No, I noticed the second I put them on my head, basically my other 3 estat amps sounded the same. The BH was very different right away regardless of volume

Huh. I wonder why you get so much STAX "fart" sounds in the first place?

I have a few estats and amps, including the BHSE, and almost never get that sound. However, we own different estat headphones except the Audeze CRBN. My CRBN had a big issue with STAX "farts", but I sent it back for repairs and Audeze replaced them with a new pair which resolved the problem.

Maybe the difference is simply the shape of heads, but I do get a good seal with the CRBN.

 

[Svperstar]

my CRBN is currently at Audeze being refurbished. You can trigger the Stax sounds by pushing on the driver and breaking the seal. I don't get them that often during normal use but I was kinda forcing the issue after noticing how different they sounded on the CRBN and the 007.

 

[Jakeh]

The fact that there is credible doubt about the validity of the initial measurements, but the author refuses to acknowledge those instead making excuses, just pulls the rug under this entire forum. That is the exact opposite of scientific. I know people here are measurement fanatics disregarding any actual listening (which ultimately is what matters, right? right..?), but you don't even play by your own rules. There is a serious lack of critical thinking in this cheerleading crowd.

 

[solderdude]

The fact that there is credible doubt about the validity of the initial measurements, but the author refuses to acknowledge those instead making excuses, just pulls the rug under this entire forum

The measurements in the initial post... sure.
Still the info from Kevin is there to read for all so readers can form their own judgement.
Pulling the rug under all ASR measurements, forums and sub-forums .. nope.

I know people here are measurement fanatics disregarding any actual listening

Ah yes .... the old 'no listening, only looking at measurements card' is getting a bit old...
Some people prefer to only see negatives and they will always find 'confirmation'.
Fortunately there is also a lot of talk about music and listening as well as psycho-acoustics here which kind of makes your remark invalid.

There is a serious lack of critical thinking in this cheerleading crowd

Is that only applicable to ASR readers/members ?

 

[milosz]

I need to be guided in my selection of audio gear - as I have limited money to buy equipment. Testing helps separate the properly designed gear from the snake oil. I don't want to experience placebo, I want to have equipment that alters the signal as little as possible.

Now, some of the measurements performed herein aren't conducted in proper context - for example you can't gauge the performance of an amplifier designed to drive electrostatic headphones by driving a resistive load like you can with other amplifier types. A resistive load is not the correct context for this kind of amplifier. And things like panel speakers are not able to be evaluated by the Klippel apparatus which assumes a quasi-point source box type speaker. In both these misguided efforts you get some data but it doesn't really tell you what you want to know about how the device performs in it's intended role. So, in some cases, the science here isn't considering if the base assumptions of the measurement technique is appropriate for the specific device under test when those devices are somewhat exotic and not typical apparatus. There's a certain hubris that just assumes if the thing is measured in the "standard" way then one learns what one needs to know, even though in some cases it is not appropriate to apply that standard methodology to somewhat more exotic apparatus.

But in no way does this invalidate the approach. It's just that in certain cases, measurement methods must be changed to be appropriate for the device under test.

And of course, the goal is to listen. But listening to the signal with as little alteration as possible, and not listening under the hypnosis of bias or placebo.

 

[BDWoody]

I know people here are measurement fanatics disregarding any actual listening (which ultimately is what matters, right? right..?), but you don't even play by your own rules. There is a serious lack of critical thinking in this cheerleading crowd.

You seem to have quite the axe to grind with this forum.

If you are going to start with that kind of nonsense, we'll just give you a bit of a break. Try interacting in good faith when you can return, or don't bother.

 

[Mr Swing King]

The fact that there is credible doubt about the validity of the initial measurements, but the author refuses to acknowledge those instead making excuses, just pulls the rug under this entire forum. That is the exact opposite of scientific. I know people here are measurement fanatics disregarding any actual listening (which ultimately is what matters, right? right..?), but you don't even play by your own rules. There is a serious lack of critical thinking in this cheerleading crowd.

This feels like a scolding from an old ex that mixed her feelings with facts.
I’m guessing here but did Amir by any chance review some of your gear unfavorably?

 

[Svperstar]

The fact that there is credible doubt about the validity of the initial measurements, but the author refuses to acknowledge those instead making excuses, just pulls the rug under this entire forum. That is the exact opposite of scientific. I know people here are measurement fanatics disregarding any actual listening (which ultimately is what matters, right? right..?), but you don't even play by your own rules. There is a serious lack of critical thinking in this cheerleading crowd.

I think another point is since Dr. Gilmore is known as an expert who designed many amps and he is the one that brought up the biggest criticisms of the measurements how come he, or another estat amp builder hasn't published their own measurements? There is a real dirth of measurements out there for estat amps. Why?