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Electrostatic Headphone Amplifier Review & Comparison
- Thread starter amirm
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Funny you mention that... I had a bit of an "experience" myself... I had the ESP/95X for a time, and relatively enjoyed them... The stock pads were super uncomfortable and provided 0 seal given the massive size of the headphones. I ended up buying some leather pads, and that did the trick. It fixed the comfort, and provided a bit more bass which was quite lacking in my opinion. Over the course of using them, I had a lot of little wonky things happen, like random static popping noises with some very mild static shock sensations every so often... That can't be good... Anyways, I mostly ignored the quirks for a while because they did sound relatively good. I think I mostly enjoyed the fact that I had a pair of "electrostatics" more than anything else...
Anyways, one day I turned on the provided amp, and put the headphones on to start a listening session, when my wife called me to ask me something. So I took the headphones off, put them down on the desk, turned around and chatted for a little with her. All of a sudden I heard this loud noise that sounded something like 20 soda cans being crushed all at the same time. We have a trash bag filled with cans to take to the recycling center every so often, so my initial thought was the dog was trying to get into it to find some food. So I called him, and he came from the side of the bed in the same room so I knew it wasn't him. That's when I noticed a loud high pitched squealing noise, and a faint smell of something burning... I turned around back to my desk and noticed that the squealing sounded like it was coming through the headphones! I Stupidly I went to put on the headphones so I could make sure it was them, but before I put the pads to my head, I also heard a bunch of super loud staticky crackling sounds coming from the headphones as well, and that's when I realized that I was about to put some 300 odd volt headphones with a clear malfunction onto my head and I threw the headphones back down on my desk... I then look at the amplifier and the power indicator light was cycling between red, yellow, green and back to to red, and as I got closer I found the smell was coming from the amp... I immediately shut it off and pulled the power... Idk what in the world happened but it was terrifying... And I can't help but think that there's a good chance my wife saved my life that day by asking me a question, prompting me to pull the headphones off and put them down on my desk... God knows what would've happened if I had the headphones on when that happened... The sound coming from the headphones was super loud, so at best it would've blown my eardrums, and at worst electric shock with high voltage directly to the head... I was beyond furious and sent a nasty-gram to drop support who promptly took them back and refunded the money...
That was the day I decided that whatever the supposed benefits of electrostatic headphones were, I didn't care, and I would never touch an electrostatic headphone ever again in my life
. With these measurements, I can also see that I'm not missing out on anything either...despite the amp not measuring well, stax is doing really great in terms of thd+n, i mean the transducers, 20 - 20 khz, tyll measured tons of cans, the only "cheap" stuff can could be on par with stax is the cheap hifiman re400 but it's earbuds
oliveoilthansnakeoil
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This is what I've always doubted and why I haven't considered stax.
solderdude
Grand Contributor
I assumed the 007 was used as a 'set'. (007 amp + 007 HP).
The 007 HP measurements make more sense when you would have used the 313 (which you sometimes call 311 and other times 313).
JustAnandaDourEyedDude
Addicted to Fun and Learning
I have always had some suspicions about EDM aka Electrostatic Destruction Music.
Funny you mention that... I had a bit of an "experience" myself... I had the ESP/95X for a time, and relatively enjoyed them... The stock pads were super uncomfortable and provided 0 seal given the massive size of the headphones. I ended up buying some leather pads, and that did the trick. It fixed the comfort, and provided a bit more bass which was quite lacking in my opinion. Over the course of using them, I had a lot of little wonky things happen, like random static popping noises with some very mild static shock sensations every so often... That can't be good... Anyways, I mostly ignored the quirks for a while because they did sound relatively good. I think I mostly enjoyed the fact that I had a pair of "electrostatics" more than anything else...
Anyways, one day I turned on the provided amp, and put the headphones on to start a listening session, when my wife called me to ask me something. So I took the headphones off, put them down on the desk, turned around and chatted for a little with her. All of a sudden I heard this loud noise that sounded something like 20 soda cans being crushed all at the same time. We have a trash bag filled with cans to take to the recycling center every so often, so my initial thought was the dog was trying to get into it to find some food. So I called him, and he came from the side of the bed in the same room so I knew it wasn't him. That's when I noticed a loud high pitched squealing noise, and a faint smell of something burning... I turned around back to my desk and noticed that the squealing sounded like it was coming through the headphones! I Stupidly I went to put on the headphones so I could make sure it was them, but before I put the pads to my head, I also heard a bunch of super loud staticky crackling sounds coming from the headphones as well, and that's when I realized that I was about to put some 300 odd volt headphones with a clear malfunction onto my head and I threw the headphones back down on my desk... I then look at the amplifier and the power indicator light was cycling between red, yellow, green and back to to red, and as I got closer I found the smell was coming from the amp... I immediately shut it off and pulled the power... Idk what in the world happened but it was terrifying... And I can't help but think that there's a good chance my wife saved my life that day by asking me a question, prompting me to pull the headphones off and put them down on my desk... God knows what would've happened if I had the headphones on when that happened... The sound coming from the headphones was super loud, so at best it would've blown my eardrums, and at worst electric shock with high voltage directly to the head... I was beyond furious and sent a nasty-gram to drop support who promptly took them back and refunded the money...
That was the day I decided that whatever the supposed benefits of electrostatic headphones were, I didn't care, and I would never touch an electrostatic headphone ever again in my life
Aha, it's nice every now and then to get some reassurance it's not paranoia.
Maki
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The same in regards to FR.
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LOL! Damn, it all makes sense now... xD
Error. I own the SR-007MKII and are great, and the SR-009s are the best headphones I've ever listened to. Although I've not listened to the high end Focals. For some reason Stax amps are not at the same level as their headphones. The problem here is that the alternatives to Stax are not very tempting. Gilmore's Blue Hawaii, and Spritzer's units have the price of an used car and not independent measurements.
kevin gilmore
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So it turns out the koss is actually 30 years old. made 7-11-1990 with opamps that have 1989 date codes. I changed out all the low voltage electrolytics and got the thd down to .009% but i don't have any of the high voltage electrolytics, will have to order them. I expect to get the numbers down to .005% which is the residual distortion on the keithely.
Look this is actually simple, you all spend thousands on amplifiers. Go and buy a quantasylum qa401 for $450. near state of the art performance on the cheap. Then build your own 20x attenuator board, or wait for me to release mine. About $50 in parts. Then you can measure 2200vpp on any of the meters you desire. AP, dscope,qa401 all have the same 100k input impedance.
Kind of surprised that no one already sells an appropriate attenuator.
Look this is actually simple, you all spend thousands on amplifiers. Go and buy a quantasylum qa401 for $450. near state of the art performance on the cheap. Then build your own 20x attenuator board, or wait for me to release mine. About $50 in parts. Then you can measure 2200vpp on any of the meters you desire. AP, dscope,qa401 all have the same 100k input impedance.
Kind of surprised that no one already sells an appropriate attenuator.
Last edited:
the_brunx
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Please keep publishing. your measurements are very useful to me. and if other people are able to push the accuracy of measurements even further than this, then let them post them also so that we can all benefit. but in the end you have awoken transparency. which will awaken progress. It's the right way forward. let's keep moving forward!
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In China they are left to ripen to the max unfortunately they say the mold that develops is related to the mold on peanuts which is carcinogenic.
OP
- Thread Starter
- #215
When we went to visit the great wall outside of Beijing, there were miles, miles and miles persimmon orchards. They were massive in size and beautiful. Once we stopped at one of the wall entrances, there were vendors selling them. I asked my colleagues to buy me some and they warned me that they would not be good to eat. I assumed pesticides but maybe they were talking about the mold? I forced them to buy one anyway and I ate it after peeling off the skin. It was incredible.
OP
- Thread Starter
- #216
You don't get near state of the art with QA401. And your resistor divider likely adds fair bit of distortion due to high voltages involved multiplied by its VCR.
That said, in the context of the tube amp it is probably OK since its distortion will swamp the above. So go ahead and build a stereo one and I will purchase it to get past all these objections.
Degru
Active Member
Degru
Active Member
Transformers are an excellent and frankly better alternative. Probably the most easily accessible one is the ifi iesl which is about $1500, but stax SRD7 Pro/mk2 (just avoid SB variants) are much cheaper if you manage to find one.. Mjolnir makes some as well but they're quite pricey. Avoid Woo Wee tho. Good components, flawed design, atrocious customer service.
Decent speaker amp paired with a transformer outperforms basically all but the best energizers.
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Good info!.
I checked, in Japan is quite cheap the SRD7
https://www.hifishark.com/model/stax-srd-7-mk-2
I flight from time to time there, so I'll have present your recommendation.
The ifi eESL model looks good. Is a clear step over the Stax offers?.
Sometimes I'm tempted to sell my SR-007MkII/SRM-727 and go for some great non-electrostatic headphone. At least, it would be very cheap to get a great amp for it. But the detail... the Stax sound is so .... god.
BTW I made (well, paid for) the Spritzer mod in the SRM-727, and definitively was better after it.
While I was measuring my newly built SRX plus, a modern-day refresh of Stax SRX designed by Jim L, I found this thread and went ahead and measured a couple of other Stax amps I have.
I'm with Amir on using the AP directly to measure the electrostatic amp output, as long as the level is carefully controlled not to exceed the safe limit. The balanced input on my SYS2722 is roughly 200k ohm in parallel with 66pf including the cables. The capacitance is fairly constant from 100Hz to 100kHz as measured on my LCR meter. Would the AP load the amp differently from the headphone? Yes. But we load the amps differently from their normal operating conditions with a dummy load all the time when we do measurements. The Stax amps are designed to drive up to 3 headphones in parallel, and a properly designed amp should not behave differently just because we have a 200k ohm AC coupled resistive loading on it. Well, measuring beasts like the KGSSHV Carbon is different story. I had to use an attenuator in order to see when the distortion takes over, and basically lost count of zeros in the measured distortion figure.
First is the DIY SRX plus. It is essentially the 3-tube per channel original SRX with the long-tail and load resistors replaced by cascode CCS.
FFT of output at approx 100V (with balanced input at 270mV):
I'd say it is pretty decent for a simple circuit like this. Comparing with the SRM-007t:
FFT of output at approx 100V (with balanced input at 120mV):
Basically they are in the same performance class. The SRX is less well matched between the channels, but has lower distortion at higher outputs (>100V). It also has slightly lower noise floor compared to the SRM-007t possibly due to difference in input levels, but higher power line related noise (not shown). Neither of them has as high as 1 or 2 percent distortion at 100V output. It is possible that Amir may have got a couple of units that have not been maintained for a long time. My SRM-007t was last serviced by me more than 10 years ago. The tubes were replaced with reasonably matched quad used JAN GEs, and the bias adjusted.
Let's take a look at an old solid-state amp from Stax, the SRM-1/MK2:
FFT of output at 100V (with 120mV unbalanced input):
The solid state amp has lower distortion, better output swings, but the noise floor is worse compared to its tube siblings. Surprise.
I'm with Amir on using the AP directly to measure the electrostatic amp output, as long as the level is carefully controlled not to exceed the safe limit. The balanced input on my SYS2722 is roughly 200k ohm in parallel with 66pf including the cables. The capacitance is fairly constant from 100Hz to 100kHz as measured on my LCR meter. Would the AP load the amp differently from the headphone? Yes. But we load the amps differently from their normal operating conditions with a dummy load all the time when we do measurements. The Stax amps are designed to drive up to 3 headphones in parallel, and a properly designed amp should not behave differently just because we have a 200k ohm AC coupled resistive loading on it. Well, measuring beasts like the KGSSHV Carbon is different story. I had to use an attenuator in order to see when the distortion takes over, and basically lost count of zeros in the measured distortion figure.
First is the DIY SRX plus. It is essentially the 3-tube per channel original SRX with the long-tail and load resistors replaced by cascode CCS.
FFT of output at approx 100V (with balanced input at 270mV):
I'd say it is pretty decent for a simple circuit like this. Comparing with the SRM-007t:
FFT of output at approx 100V (with balanced input at 120mV):
Basically they are in the same performance class. The SRX is less well matched between the channels, but has lower distortion at higher outputs (>100V). It also has slightly lower noise floor compared to the SRM-007t possibly due to difference in input levels, but higher power line related noise (not shown). Neither of them has as high as 1 or 2 percent distortion at 100V output. It is possible that Amir may have got a couple of units that have not been maintained for a long time. My SRM-007t was last serviced by me more than 10 years ago. The tubes were replaced with reasonably matched quad used JAN GEs, and the bias adjusted.
Let's take a look at an old solid-state amp from Stax, the SRM-1/MK2:
FFT of output at 100V (with 120mV unbalanced input):
The solid state amp has lower distortion, better output swings, but the noise floor is worse compared to its tube siblings. Surprise.
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