Electrostatic Headphone Amplifier Review & Comparison

[isiora]

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?

Stax publishes its measurement results in the product specifications. As I have already written in this thread, those who think these statements are false should consider the reputation and history, over 80 years, of the brand.
I am an experienced electronics engineer and I make a living from my work. I have published in this thread the measurements I have personally made on my SRM-006tS, which show that they are good, yet in the opening pages of this thread there are still the incorrect measurements of Amir. And there are also other incorrect statements such as "Here is the SMR-006t which is also tube based but its output is not differential:". It's not true! The SMR-006t is fully differential (and impedance balanced), as you can already see from the block diagram I attach below. And again about the measurement system, Amir says "AP's 'unbalanced' input is floating so nothing was reference to ground but to the differential pair", which is not true. In fact AP's specifications say that the shield of the unbalanced input goes to ground with an impedance of 500Ohm||1uF, and this means that he has practically grounded one of the differential outputs (considering the left channel, L- or L+). This is further demonstrated by the fact that in all the measurements made by Amir of all the Stax, the second harmonic is higher than the third which is not what we should expect from this type of amplifiers.

 

[isiora]

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...

No. In fact your measurements are aligned with those I made on my SRM-006tS, which is the original without CCS. The measurements reported in the first pages of this thread are wrong. I explained the reasons in my posts.

 

[solderdude]

This is further demonstrated by the fact that in all the measurements made by Amir of all the Stax, the second harmonic is higher than the third which is not what we should expect from this type of amplifiers.

Balanced outputs often have higher 3rd harmonic than 2nd harmonic for the simple reason that SE 2nd harmonic and the inverse phase of that also having similar 2nd harmonic combines to 3rd harmonic distortion in balanced output.

 

[isiora]

Balanced outputs often have higher 3rd harmonic than 2nd harmonic for the simple reason that SE 2nd harmonic and the inverse phase of that also having similar 2nd harmonic combines to 3rd harmonic distortion in balanced output.

I don't understand what you wanted to clarify. In fact, I wrote that even harmonics cancel out (and odds sum up, obviuosly), and that is what we do NOT see in Amir's measurements. I don't understand also what you mean with "...combines to 3rd harmonic distortion...". 2nd order not combine to form 3rd! Even orders simply cancel out.
More precisely, in the balanced case, we can rougly write:
v+ = a*vi + b*vi^2 + c*vi^3 + ...
v- = -a*vi + b*vi^2 - c*vi^3 + ...
vdiff = v+ - v- = 2a*vi +2c*vi^3 + ...
vi^2 does not appear with the - sign in v- because (-vi)^2 = vi^2

 

[solderdude]

Yep, something went wrong with editing between both 'to a' the bold part was accidentally deleted and did not notice it.

Balanced outputs often have higher 3rd harmonic than 2nd harmonic for the simple reason that SE 2nd harmonic and the inverse phase of that also having similar 2nd harmonic combines to a lower level 2nd harmonic distortion which is not shown in the measurements. As odd harmonics add this leads to a higher 3rd harmonic distortion in balanced output.

 

[isiora]

Yep, something went wrong with editing between both 'to a' the bold part was accidentally deleted and did not notice it.

Balanced outputs often have higher 3rd harmonic than 2nd harmonic for the simple reason that SE 2nd harmonic and the inverse phase of that also having similar 2nd harmonic combines to a lower level 2nd harmonic distortion which is not shown in the measurements. As odd harmonics add this leads to a higher 3rd harmonic distortion in balanced output.

This is better.

 

[isiora]

Yep, something went wrong with editing between both 'to a' the bold part was accidentally deleted and did not notice it.

Balanced outputs often have higher 3rd harmonic than 2nd harmonic for the simple reason that SE 2nd harmonic and the inverse phase of that also having similar 2nd harmonic combines to a lower level 2nd harmonic distortion which is not shown in the measurements. As odd harmonics add this leads to a higher 3rd harmonic distortion in balanced output.

Note however that while it is true that the 3rd sums up, also the fundamental sums up, so the ratio is unchanged and the 3rd remains percentually the same, not higher.

 

[LTig]

Note however that while it is true that the 3rd sums up, also the fundamental sums up, so the ratio is unchanged and the 3rd remains percentually the same, not higher.

No, 3rd harmonica is usually higher because the individual amplifier must deliver twice the current compared to unbalanced mode, which usually means more THD.

 

[isiora]

No, 3rd harmonica is usually higher because the individual amplifier must deliver twice the current compared to unbalanced mode, which usually means more THD.

Really?!?
Why on earth, given the same effective output voltage, should it provide double the current? Please, explain.

 

[LTig]

Really?!?
Why on earth, given the same effective output voltage, should it provide double the current? Please, explain.

Not at the same output voltage, that's correct.

If the power of a stereo amp in stereo mode is not sufficient you can use it in bridged mode to get ~4 times the power. Then each amp stage sees have the load impedance and - if driven to max output voltage - must deliver twice the current compared to stereo mode. This comes with higher distortion where even order components cancel and odd order add up.

This does not apply if you compare two amps with the same output power where one works balanced and the other unbalanced.

 

[isiora]

Not at the same output voltage, that's correct.

Don't be offended, but then we're talking about nothing.

 

[TLEDDY]

Just a little bit of humor - when non-native English speakers try to write ads:

“Topping EHA5 Headphone Amp 12V Trigger Interface AMP Electrostatic Headphone Amplifier Balanced Amp

* With the EHA5's *appalling* signal-to-noise ratio and excellent noise control, the noise that can be heard is gone.“

This from Amazon; asterisks added to call attention!

Tillman

 

[Zooqu1ko]

Just a little bit of humor - when non-native English speakers try to write ads:

“Topping EHA5 Headphone Amp 12V Trigger Interface AMP Electrostatic Headphone Amplifier Balanced Amp

* With the EHA5's *appalling* signal-to-noise ratio and excellent noise control, the noise that can be heard is gone.“

This from Amazon; asterisks added to call attention!

Tillman

And here's the Amazon link: https://www.amazon.com/dp/B0C22SPD57

on Amazon.de, the SNR is "erschreckend", i.e. frightening.

 

[SpaceMonkey]

Hi, anyone actually tried Topping EHA5? I am thinking how to connect this one to Stax SR001. Does the amp make any difference of IEMs fall before the amp?

 

[TLEDDY]

Hi, anyone actually tried Topping EHA5? I am thinking how to connect this one to Stax SR001. Does the amp make any difference of IEMs fall before the amp?

I have one on order… will report after arrival. I acquired the rectangular “Professional “, the ultra high end -09S, an entry level set along with SRM007Tiio amp and 4NOS tubes. Lists over $10K for $1000 from an estate sale.

While the tube amp seems stupid good to my ear, the little solid state Stax is anemic (Audiophool-speak meaning i don’t care for it). I want to see how EHA5 compares.

 

[TLEDDY]

I have one on order… will report after arrival. I acquired the rectangular “Professional “, the ultra high end -09S, an entry level set along with SRM007Tiio amp and 4NOS tubes. Lists over $10K for $1000 from an estate sale.

While the tube amp seems stupid good to my ear, the little solid state Stax is anemic (Audiophool-speak meaning i don’t care for it). I want to see how EHA5 compares.

OK - the unit has arrived! To my (deaf) ears, it is the equal of the tubed Stax Amp, perhaps not as euphonic as the tubes, but certainly worth the money in its improvement over the little Stax amp.

I do not need three sets of Stax amps and speakers. After I decide which one pleases me the most, I will list in the Members For Sale section

Tillman