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Why aren't many solid-state based electrostatic amplifiers, specially for headphones?

KeithPhantom

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Right now I'm in the market for a Stax SR-009(S) and I'm in the search for an amplifier to go with it. My issue is there are a lot of tube (valve)-based ones, and this is a deal-breaker for me. I'm not assuming those valve amplifiers measure bad (we just don't know), I just do not like valves and prefer the reliability and looks of solid-state gear. The question is, can you recommend an electrostatic amplifier that is SS based and measures good? Also, why aren't many measurements of these kind of amps and why so many are tube based?

I know valves can handle high voltages nicely and Stax makes their own amps, buy I would like to see more options in the market. Also, you can make high voltage SS circuits as well, so why not more?
 

maverickronin

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It's a small niche market so there's very little demand for someone to hook up one of their expensive audio analyzers to one.

AFIK, the only good alternatives to Stax's own amps are the Kevin Gilmore designs. IIRC there are several new solid state designs he's done in recent years.

Personally though, with the lack of credible data, I'd just get a SRM-353X.
 
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KeithPhantom

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High voltage silicon parts are rare and don't perform as well as Tubes. That's why. People who see tubes and immediately jump on that they are crap are clueless.
Hybrid is the way to go.
I know (the reason I said I'm not assuming), but I'm pretty rough with my gear and expect it to not break and have the issues tubes bring (I'm not buying tubes every two years, not waiting for them to warm up...). Also, why not ask for advise so my electrostatic gear is up to level to my normal gear.
 

JohnYang1997

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I know (the reason I said I'm not assuming), but I'm pretty rough with my gear and expect it to not break and have the issues tubes bring (I'm not buying tubes every two years, not waiting for them to warm up...). Also, why not ask for advise so my electrostatic gear is up to level to my normal gear.
Well. Generally the amp itself will have higher distortion than the headphone itself. In total around 0.01% best for all headphones.
Tubes in electrostatic headphone amps don't break easily. They run on very low current. It takes less than 10 seconds to listen to music. So basically turn the amp on, put your headphones on, click play you should hear the music in 1-2 seconds.
 
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KeithPhantom

KeithPhantom

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I also want to ask the question why tubes in regular audio applications distort more than tubes used in electrostatic amplifiers. Even Sennheiser used them in their HE-1 system while claiming 0.01% THD at 1 kHz.
 

JohnYang1997

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I also want to ask the question why tubes in regular audio applications distort more than tubes used in electrostatic amplifiers. Even Sennheiser used them in their HE-1 system while claiming 0.01% THD at 1 kHz.
It's not the tubes. I've made 0.0000x% Thd with tube input stage. It's the people who choose to use tubes to design circuits that don't call for tubes. They generally aren't great engineers and don't care about measurements hence measure poorly. The same people will make bad electronics no matter what components they use.
However tho, 0.01% is not that good in line level. A few tube related products measured here have better performance than that.
 
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KeithPhantom

KeithPhantom

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It's not the tubes. I've made 0.0000x% Thd with tube input stage. It's the people who choose to use tubes to design circuits that don't call for tubes. They generally aren't great engineers and don't care about measurements hence measure poorly. The same people will make bad electronics no matter what components they use.
However tho, 0.01% is not that good in line level. A few tube related products measured here have better performance than that.
Well, I think they're claiming that including the headphone, that's -80 dB and a lot for a headphone.
 

maverickronin

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Well, I think they're claiming that including the headphone, that's -80 dB and a lot for a headphone.

'Stats are clean. .01% is a top of the class number, not some kind of mythical holy grail.

Even Sennheiser used them in their HE-1 system while claiming 0.01% THD at 1 kHz.

Reading between the lines of their marketing material those tube are basically just pretty lights to lure in rich whales to buy it.

They claim to have MOSFETs integrated into the cups as the output stage. That makes the tubes an input or intermediate gain stage at best and not something which requires their high voltage charateristics. I'm pretty sure they're just 6922/ECC88's which are small signal low voltage preamp tubes. (Though a quick google didn't confirm what type because Senn wants you to only buy custom branded replacements from them...)
 
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KeithPhantom

KeithPhantom

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'Stats are clean. .01% is a top of the class number, not some kind of mythical holy grail.
The distortion seems too low for mechanical instruments; if those numbers are real deal up to the transducer level, not just the HE-1, also for other examples, I would be exploring more transducers of that kind.
 
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KeithPhantom

KeithPhantom

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It's not the tubes. I've made 0.0000x% Thd with tube input stage. It's the people who choose to use tubes to design circuits that don't call for tubes. They generally aren't great engineers and don't care about measurements hence measure poorly. The same people will make bad electronics no matter what components they use.
But going back to the topic, even having tubes, there are almost no electrostatic amplifier measurements, thus it is hard to assess the engineering underlying the product. How do I know if the implementation of the tubes is correct and clean?
 

JohnYang1997

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But going back to the topic, even having tubes, there are almost no electrostatic amplifier measurements, thus it is hard to assess the engineering underlying the product. How do I know if the implementation of the tubes is correct and clean?
Several things

Electrostatic is a niche product. It maybe a bit different now but it's still way different from what mass market produce. So less measurements for less "popular" products are understandable.

It's much more difficult to measure high voltage signal. You would need attenuator. And the attenuator needs to be very high input impedance to not load down the amplifier. Then the noise measurements may not be very accurate.

In combination of the two. It's a small market. No one would do standardized measurements equipment for it. So to perform test it relies on DIY basically. For reviewers, it's something that takes too much effort and won't be used too often. Or majority don't simply have the money to buy a few of them. Electrostatic headphones themselves are more interesting even.
 
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KeithPhantom

KeithPhantom

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It is impressive to see 0.01% THD in certain frequencies/levels for transducers (I have the LCD-2F), this makes me wonder what is the future of headphone design and engineering in terms of pushing the envelope of what can be done. I would like to see an explosion such as that one of DACs, getting better and better measurements as time goes on.
 
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KeithPhantom

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It's much more difficult to measure high voltage signal. You would need attenuator. And the attenuator needs to be very high input impedance to not load down the amplifier. Then the noise measurements may not be very accurate.
Interesting, but these challenges will have to be solved somehow. You can design by ear, but that will take you so far. I would love to have a better method to measure these amps, because I was eager to see at least some kind of measurement.
 

JohnYang1997

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It is impressive to see 0.01% THD in certain frequencies/levels for transducers (I have the LCD-2F), this makes me wonder what is the future of headphone design and engineering in terms of pushing the envelope of what can be done. I would like to see an explosion such as that one of DACs, getting better and better measurements as time goes on.
Well. I certainly what the frequency response to be better. At least comparable to speakers. Low THD is good but it doesn't stop me from listening to er4 with 0.7% THD.
 

JohnYang1997

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Interesting, but these challenges will have to be solved somehow. You can design by ear, but that will take you so far. I would love to have a better method to measure these amps, because I was eager to see at least some kind of measurement.
I was mainly aiming at distortion and noise measurements. For other measurements it can be done quite easily using oscilloscope.
 
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KeithPhantom

KeithPhantom

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Well. I certainly what the frequency response to be better. At least comparable to speakers. Low THD is good but it doesn't stop me from listening to er4 with 0.7% THD.
Me too, my HD6XXs have 2% distortion around 20 Hz and I don't mind, but from an engineering point, it is always welcomed to make improvements.
 

bigjacko

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I have seen that koss ESP9/X energizer claim to has thd+n 0.001%, stax only have 0.01%. But most people still say stax energizer sound better which I don't understand why, anyone knows why?
 
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KeithPhantom

KeithPhantom

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I have seen that koss ESP9/X energizer claim to has thd+n 0.001%, stax only have 0.01%. But most people still say stax energizer sound better which I don't understand why, anyone knows why?
It is pretty hard to evaluate the performance of electrostatic amplifiers if there are no independent measurements, I don't trust a lot in what many manufacturers publish and prefer to trust more in public sites like this.
 
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