• WANTED: Happy members who like to discuss audio and other topics related to our interest. Desire to learn and share knowledge of science required as is 20 years of participation in forums (not all true). Come here to have fun, be ready to be teased and not take online life too seriously. We now measure and review equipment for free! Click here for details.

Electrostatic Headphone Amplifier Review & Comparison

Degru

Active Member
Joined
Feb 19, 2019
Messages
230
Likes
223
Location
Beaverton, OR
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.
The iESL is about as good as an srd7mk2 from what ive been told, but much more feature rich and can be bought new. It also has an advantage with normal-bias cans due to the way the bias circuit works which makes some cans that would otherwise have an imbalance, not have an imbalance since it charges the diaphragms evenly even if the coating on one is worn off, or something.

For that price range I'd rather go for a unit that uses beefier transformers, tho you typically have to have those custom built and it's not as simple as clicking buy on an order page or auction.

And yeah, I don't think there's anything that beats Stax on detail.
 
Last edited:
Joined
Aug 31, 2019
Messages
84
Likes
80
Location
Arad, Romania
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...
Current is very low though so you wouldn't die even if you directly touched the stator.
 

solderdude

Major Contributor
Joined
Jul 21, 2018
Messages
9,141
Likes
19,509
Location
The Neverlands
Besides, when listening there is also a high voltage present but NOT opposite ground which would be the 'shocking' part.
Totally safe.. the burning amp is another worry though. Competently designed equipment should NOT go up in flames.
 
Joined
Feb 29, 2020
Messages
37
Likes
185
You want some numbers, here are some numbers.

kgsshv carbon with 450v power supplies and 18ma output stage bias current
thd < .005% 20hz to 20khz at 1600vpp into 120pf load in parallel with 1Megohm meter load
thd < .005% 20hz to 20khz at 1600vpp into 120 pf load in parallel with 1Megohm meter load in parallel with 200kohm resistor string

anyone want to prove me wrong, go ahead please. i'll wait.

srm-007t (correction)
there are actually at least 3 different versions of this, but i would think that all should measure about the same
first version is buffered grid drive
second version is buffered grid drive with constant current cascode.
third version is buffered grid drive with constant current cascode and regulated dc filament supply

Evidently this third version is causing some issues in the field with noticeable audible distortion. Due to the filament capacitor
in the power supply. Happens all of a sudden.

Although there are a couple of stax amps with 3 output jacks, i don't think it was ever the intent to drive 3 headphones at the same time.

these are cheap. 4 needed to measure stereo
https://www.goldmine-elec-products.com/prodinfo.asp?number=G24876
 
Last edited:
Joined
Aug 31, 2019
Messages
84
Likes
80
Location
Arad, Romania
You want some numbers, here are some numbers.

kgsshv carbon with 450v power supplies and 18ma output stage bias current
thd < .005% 20hz to 20khz at 1600vpp into 120pf load in parallel with 1Megohm meter load
thd < .005% 20hz to 20khz at 1600vpp into 120 pf load in parallel with 1Megohm meter load in parallel with 200kohm resistor string

anyone want to prove me wrong, go ahead please. i'll wait.

srm-007t (correction)
there are actually at least 3 different versions of this, but i would think that all should measure about the same
first version is buffered grid drive
second version is buffered grid drive with constant current cascode.
third version is buffered grid drive with constant current cascode and regulated dc filament supply

Evidently this third version is causing some issues in the field with noticeable audible distortion. Due to the filament capacitor
in the power supply. Happens all of a sudden.

Although there are a couple of stax amps with 3 output jacks, i don't think it was ever the intent to drive 3 headphones at the same time.

these are cheap. 4 needed to measure stereo
https://www.goldmine-elec-products.com/prodinfo.asp?number=G24876
Are you the designer of these amps? You could send one in if you want them measured with industry standard gear.
 

brimble

Active Member
Forum Donor
Joined
Oct 18, 2020
Messages
111
Likes
135
Location
Australia
Not only was I already grateful for this review, but one of my two Stax amps has just broken, and since I always like to have a spare I'll be buying another one, so now I'm doubly grateful. I've made a donation (and in fact had also already donated under a different name).

NOW, would anybody like to guess whether the small Stax amps that take an external power supply are as good as the solid state Stax amps that have built-in power supplies? My listening tests suggest yes (I've never been able to hear any differences between any of the solid state Stax amps, from the cheapest to the most expensive), but I'd welcome other guesses (or, even better, measurements if anyone has any).
 

Memoryerror

Member
Forum Donor
Joined
Jun 12, 2018
Messages
41
Likes
18
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...
From my limited understanding it sounds like you may have developed an ark between stators. Again in my limited understanding, it sounds like you may have developed a hole(s) in the diaphragm(s) when the popping happened prior was probably the diaphragm sticking to the stator. A good practice to avoid holes in the diaphragm is when you have a pop to imidiately unplug the headphones and touch a finger to the pins to discharge the headphones. It is also good practice to do this each time after listening to electrostatic headphones from what I understand.

The diagram can get stuck to the stators when you have a good seal between the earpads and your head and the air pressure or suction pushes or pulls the diaphragm into one of the stators. So that is probably why you did not experience it before changing pads.
 
Last edited:

bobbooo

Major Contributor
Joined
Aug 30, 2019
Messages
1,479
Likes
1,984
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).
You were right the first time. Here's an overlay of the frequency response plus distortion graph of the SR-007 driven by the 'mystery' amp, and frequency response-only measurements of the the same headphone driven by the SRM-007t tube amp as shown in this post:

proof.gif


As can clearly be seen, the blue frequency response curve of the FR+distortion graph matches exactly with one of the measurements (the red curve) of the FR-only graph of the headphones driven by the SRM-007t tube amp, so the distortion graph must be from the same measurement of this very same amp. It simply isn't possible for a headphone's distortion to be as low as -60dB at 1kHz when driven by an amp with much higher supposed distortion of -35dB at 1kHz. As for the argument that the former figure doesn't include higher harmonic distortion orders, even being (extremely) generous to this argument and assuming the 4th-20th harmonics are all at -60dB, close to the 2nd harmonic above (despite the amp harmonics decreasing in level with frequency from the review measurements), the THD from all these combined harmonics would add up to only around -47dB, still way below the -35dB measured THD of the tube amp alone. The amp measurements in this review simply do not add up, contradicted not only by ASR's previous measurements, but now by other users' results too. As previously stated, the likely reason for this is the inadequate impedance of the AP analyzer for testing electrostatic amps.

Oh and I want to make something 100% clear - I am most certainly not a fan of Stax amps, nor their headphones for that matter. You would never catch me falling hook, line and sinker for mythical audiophool claims the company and Stax owners perpetuate and wasting thousands of dollars on multiple glorified tube amps, when electrostatic amps (and headphones) from other companies with equally inaudible distortion can be had for a fraction of the price. Regardless of my personal opinion of them however, what I am a fan of is careful scientific testing and analysis that reliably and fairly leads to truth. I am not a fan of calling a result based on incomplete data (in any context), and jumping to unfairly rash, unfounded conclusions based on singular measurements under test conditions that are poor approximations of real-world usage.
 
Last edited:

solderdude

Major Contributor
Joined
Jul 21, 2018
Messages
9,141
Likes
19,509
Location
The Neverlands
This is the measurement taken of the same SR-007 headphone but driven from the SRM-313 amp

1604556474626.png


Below the 'average' of several slightly different seated positions using the SRM-007t amp. Not fully comparable perhaps as this seems to be a single measurement. Also note the frequency axis on the plots is not the same.
1604556662829.png


This suggests indeed that the distortion measurements were taken on the SR007t amp and not the SR313 amp.
The reason I say it looks this way is not based on differences in plots above 2kHz (averaged vs. not averaged causes this) but the differences in response at 30Hz.

Below another SR-007 Stax measured by Tyll
Stax Tyll.png

The plot above is closer to Amir's measurements than the example Amir used in his post (the plot below)
Not all SR007 seem to be created equal. The plot below indicates moving it around shows seal issues where the one above either always had poorer seal or maybe another amp was used ?
Perhaps on the legacy website going back far enough may reveal test conditions and amps.

1604560300243.png


In the pdf of both SR-007 measurements both for 90 and 100dB SPL the THD over the entire band remained below 0.1%.

I don't own Stax stats (owned an elecret) because of the creaky plastic and need for energizers (usually mains fed) and the potential problems after a long time. That and the costs of a system. The 007 and 009 clearly are more rigidly built... but the price...
The Sonoma and some other stats clearly have the edge when it comes to construction.

I really like the sound sig of those I heard. Maybe a tad too light in the bass but otherwise likable.
 
Last edited:

Cortes

Active Member
Joined
Apr 13, 2019
Messages
287
Likes
330
Not only was I already grateful for this review, but one of my two Stax amps has just broken, and since I always like to have a spare I'll be buying another one, so now I'm doubly grateful. I've made a donation (and in fact had also already donated under a different name).

NOW, would anybody like to guess whether the small Stax amps that take an external power supply are as good as the solid state Stax amps that have built-in power supplies? My listening tests suggest yes (I've never been able to hear any differences between any of the solid state Stax amps, from the cheapest to the most expensive), but I'd welcome other guesses (or, even better, measurements if anyone has any).
Not surprised. Pls, can you share what models you are referring to?.
 
Joined
Oct 8, 2019
Messages
91
Likes
196
Location
Portugal
The reason I say it looks this way is not based on differences in plots above 2kHz (averaged vs. not averaged causes this) but the differences in response at 30Hz.
Bass on electrostatics is largely dependent on seal. I would not attribute the 30Hz change to the amp, but to the sealing of the pads. Here are the oratory1990 measurements of my 007 unit, various reseats:

no blutack 007.png


This is without the blue-tack mod, so the pads would never seal completely, hence the bass roll-off.
 

solderdude

Major Contributor
Joined
Jul 21, 2018
Messages
9,141
Likes
19,509
Location
The Neverlands
Indeed it is determined by the seal.
This is easily confirmed by Tyll's and Amir's measurements as well.

The thing Oratory's measurements do not show is the exact same headphone on the same rig with the only difference being the amplifier.

I have measured a few dynamic headphones on different amps and the FR does not change (unless output R is substantially different) or an output cap is present and not well designed. Very measurable and straightforward techniques that have been well documented and can easily be measured with actual and resistive loads.

The thing in this particular case is different as the amps in question are NOT measured under real life conditions but under conditions that are assumed to be relevant.
In the lows a stat has no real load. It is just a capacitance that is easily charged. It is in no way comparable to 2 100k to ground loads or 200k differential loads.
As long as the exact output circuit is not known and taken into consideration we don't know exactly how it performs. Kevin G probably has by far the most experiences in this.

The point bobbooo tries to make is that indeed the 007 amp was used and not the SS.
These 2 amps are so fundamentally different in design and above all the output stage that cannot guarantee bass response will be the same on different amps under actual loads (it basically is no load at all for lows).
The measurement of the same headphone (on the same rig ?) with the same seal (when the same rig) should have comparable results (at least the case for dynamics). For the treble differences are obvious. For the bass response less so.

In any case, untill Amir says different rigs, different headphone or different seal the most obvious differences are in the lows in this case.
And as that differs it will be hard to defend the distortion measurements would be done with SS (hence the lower distortion).

That's the point. As there are so little directly comparable measurements of amps under similar conditions with just 1 headphone the idea of Amir measuring amps under similar and 'deep digging' measurements is highly applauded.
However, I have doubts the test load is not similar to an actual load, not similar enough which might (and probably does) skew results.

Amir has measured much more equipment than I ever will and access to test gear I can only dream of and have not done a single measurement on any real stat ever that this is just a 'hunch' on my part because of knowledge of electronics.
Personally I would like to see the same tests redone with a front-end as proposed by Kevin (can't be hard to build) and accuracy doesn't even have to be in the 0.000x % at all as that won't be reached without extreme open loop gains.

Maybe Amir will, maybe he won't for reasons he decides himself. It's his website and no one else's.
In this case the difference in bass levels may not be a seal issue but could (doesn't have to be) an amp (load) difference.
Oratory probably hasn't used different amps but either used the one you sent along or one he has so is not conclusive as evidence.
Only FR of your 007 on the used amp is conclusive and alone on that rig and the circumstances at that time.
 

Cortes

Active Member
Joined
Apr 13, 2019
Messages
287
Likes
330
I've always powered my SRM-727MKII with RCA, is it worth using XLR's?. I have some XLRs built myself but I'm quite skeptical about their quality.
 

Robin L

Major Contributor
Joined
Sep 2, 2019
Messages
2,792
Likes
3,496
Location
1 mile east of Sleater Kinney Rd
I still have my Stax SRM T1 amp energizer, from back in 1988:

D3S_5315-front-0640.jpg


This was considered over the top in cost at the time. I also had the Stax Lambda Professional headphones:

D3S_4916-0600.jpg




To be honest, these were the best tools for my purposes at the time. The biggest flaw was the cord for the headphone. I take that back, the biggest flaw was my severe case of audiophilius nervosa: I made a fixed resistor bypass for the potentiometer, replaced all passive components [resistors, caps, wire] with "high-end" substitutes. Managed to destroy a JFET in the process. Fortunately there was a nearby audio repair shop that could fix it, being as this was Berkeley in the nineties and there was quite the audiophile scene in the town at the time. I managed to wear out/destroy two Lambda type 'earspeakers', and by the time that all happened, I was out of the business of recording other musicians anyway.

If I was in the same situation today, I would use what I've got now. I wouldn't have been aware of this bit of kit unless I read ASR. I've got Drop 6XX headphones and the mini-stack of Topping E/L 30, hooked up to an Acer Aspire 5, which appears to be the cheapest decent Windows laptop right now [$364.00]. Mostly I'm listening to Apple Lossless files from a flashdrive that holds half a terabyte. Some of the files are MP3 of different data rates, some are uncompressed Redbook. Otherwise it's whatever's streaming, YouTube, Tidal, various sources for TV.

Clearly it's a different world now than when I first got the Stax amp & 'phones. They probably were the most refined and detailed sounding transducers I've encountered, but they also had plenty of problems, many of which are addressed by the Drop-Topping combo. First, the cord connecting the earspeakers to the energizer amp was just a little bit too long and difficult to replace. Alas, I had the wheels of my desk chair run over that cord once too often (twice!). Also, expensive to replace the cord, and not easy to replace. The Drop 'phones use a cord that's easy to replace, not too long and not expensive. There might have been more detail and nuance in the earspeakers, but that also could be due to elevated treble as the sound could get harsh. Bass was clear and clean, too bad there never was quite enough of it. The Drop 6xx's are similarly light in the deep bass [also overcooked for the next three octaves, an issue the Stax did not have], but there's the APO EQ to iron that out, and that treatment really works, as Solderdude notes elsewhere. If the Drop headphones seem to have a little less treble detail, that might be on account of my encroaching deafness. No question that the Topping amp and Drop headphones can play a lot louder, though that's not really an advantage for me.

These reviews [Warning: contains subjective content] align with my memories for the most part.

https://www.kenrockwell.com/audio/stax/srm-t1.htm

https://www.kenrockwell.com/audio/stax/sr-lambda-pro.htm

If a pair of Lambda 'phones were to drop into my lap, I'd drag out the SRM T1 out of storage, but that's about it for me. It's just one more thing in my rear-view mirror.
 
Last edited:

the_brunx

Active Member
Joined
Apr 7, 2020
Messages
168
Likes
368
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.
This!!!
 

Robin L

Major Contributor
Joined
Sep 2, 2019
Messages
2,792
Likes
3,496
Location
1 mile east of Sleater Kinney Rd
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.
I hooked my Stax headphones to a Marantz 8b with one of those. Very strange. Everything in the mids was holographic, deep bass was absent, as were the top two octaves. Best combo ever for Sarah Vaughan and Ella Fitzgerald records. Goof click, pop and rumble filter.
 

Frank Dernie

Major Contributor
Forum Donor
Joined
Mar 24, 2016
Messages
5,634
Likes
12,676
Location
Oxfordshire
I still have my Stax SRM T1 amp energizer, from back in 1988:

View attachment 91581

This was considered over the top in cost at the time. I also had the Stax Lambda Professional headphones:

View attachment 91582



To be honest, these were the best tools for my purposes at the time. The biggest flaw was the cord for the headphone. I take that back, the biggest flaw was my severe case of audiophilius nervosa: I made a fixed resistor bypass for the potentiometer, replaced all passive components [resistors, caps, wire] with "high-end" substitutes. Managed to destroy a JFET in the process. Fortunately there was a nearby audio repair shop that could fix it, being as this was Berkeley in the nineties and there was quite the audiophile scene in the town at the time. I managed to wear out/destroy two Lambda type 'earspeakers', and by the time that all happened, I was out of the business of recording other musicians anyway.

If I was in the same situation today, I would use what I've got now. I wouldn't have been aware of this bit of kit unless I read ASR. I've got Drop 6XX headphones and the mini-stack of Topping E/L 30, hooked up to an Acer Aspire 5, which appears to be the cheapest decent Windows laptop right now [$364.00]. Mostly I'm listening to Apple Lossless files from a flashdrive that holds half a terabyte. Some of the files are MP3 of different data rates, some are uncompressed Redbook. Otherwise it's whatever's streaming, YouTube, Tidal, various sources for TV.

Clearly it's a different world now than when I first got the Stax amp & 'phones. They probably were the most refined and detailed sounding transducers I've encountered, but they also had plenty of problems, many of which are addressed by the Drop-Topping combo. First, the cord connecting the earspeakers to the energizer amp was just a little bit too long and difficult to replace. Alas, I had the wheels of my desk chair run over that cord once too often (twice!). Also, expensive to replace the cord, and not easy to replace. The Drop 'phones use a cord that's easy to replace, not too long and not expensive. There might have been more detail and nuance in the earspeakers, but that also could be due to elevated treble as the sound could get harsh. Bass was clear and clean, too bad there never was quite enough of it. The Drop 6xx's are similarly light in the deep bass [also overcooked for the next three octaves, an issue the Stax did not have], but there's the APO EQ to iron that out, and that treatment really works, as Solderdude notes elsewhere. If the Drop headphones seem to have a little less treble detail, that might be on account of my encroaching deafness. No question that the Topping amp and Drop headphones can play a lot louder, though that's not really an advantage for me.

These reviews [Warning: contains subjective content] align with my memories for the most part.

https://www.kenrockwell.com/audio/stax/srm-t1.htm

https://www.kenrockwell.com/audio/stax/sr-lambda-pro.htm

If a pair of Lambda 'phones were to drop into my lap, I'd drag out the SRM T1 out of storage, but that's about it for me. It's just one more thing in my rear-view mirror.
I bought the same at about the same time. Mine are little used and back in their boxes in storage. I discovered I preferred well positioned speakers even if the room did interfere a bit.
 

the_brunx

Active Member
Joined
Apr 7, 2020
Messages
168
Likes
368
I hooked my Stax headphones to a Marantz 8b with one of those. Very strange. Everything in the mids was holographic, deep bass was absent, as were the top two octaves. Best combo ever for Sarah Vaughan and Ella Fitzgerald records. Goof click, pop and rumble filter.
Must be a problem somewhere. I just got one (SRD7 pro) two days ago hooked it today to a pioneer amp. it sounds as clean as ever with way more power than any other Dedicated STAX amp I have ever listened to. I wish I knew this sooner.
 
Last edited:

Robin L

Major Contributor
Joined
Sep 2, 2019
Messages
2,792
Likes
3,496
Location
1 mile east of Sleater Kinney Rd
Must be a problem somewhere. I just got one two days ago hooked it today to a pioneer amp. it sounds as clean as ever with way more power than any other Dedicated STAX amp I have ever listened to. I wish I knew this sooner.
Most likely old tube amp design, with its attendant audible distortions. Hooked it up the same way to a solid state amp, heard solid state grain.
 
Top Bottom