Gramophone Dreams #58: Stax SR-X9000 headphones, EAR Phono Classic, Bob's Devices Sky 20 SUT

A month ago, I ran into my Russian neighbor in the hall. As usual, he asked me what I was reviewing. (Vladimir likes to come over and listen, then find fault with everything I play.) When I told Vlad I had Stax's new top-of-the-line earspeaker, the SR-X9000, he lit up and exclaimed, "I need to hear it," adding that he has been a lifelong Stax fanatic and owns at least five different models, "dating way back." He told me he'd recently sold his SR-009 to buy the newer SR-009S, but he still has his ragged, 25-year-old Stax Omega "prototype," which sounds "even better" than the 009S. I told him I'd never heard that model and suggested he bring it by so that we could compare it to Stax's latest "best" headset.

He frowned. "It's hidden in my room. I do not use them much at the moment, and no they are not for sale." He promised a picture instead. "They're really heavy, made of solid brass—and gold plated!"


Vlad's prototype of the original Stax SR-Omega.

When I asked what the Omega sounded like, he laughed. "That headphone is a dream, Herb! So open, rich, and beautiful sounding. The bass is full although not as punchy as one might hope." I begged him to find his gold-plated Omega and let me try it (footnote 1).

Stax SR-X9000
Stax's new, big, expensive SR-X9000 electrostatic headphone ($6200, footnote 2) presents recordings with a purity, tonal neutrality, rhythmic ease, and resolve that I have not previously experienced with headphones—ever, whether dynamic, planar-magnetic, or electrostatic. Not even with Stax's own SR-009S. On each of my most-played recordings, the SR-X9000 avoided blur, fuzz, dragging feet, and what-was-that-lyric confusion. It left no veils unlifted.

Which does not mean that every audiophile will think the new Stax is the best headphone ever—nor that they would choose it as their one-and-only. Competition for Best Headphone is beyond fierce. I encourage everybody to audition all contenders before buying, even the ones you can't afford.


Description: According to my Russian friend, Stax developed the Omega as an experiment. Their goal was to increase the size of the SR-X's metal-mesh electrodes. (Vlad said he still uses his SRX-IIIs.) Stax engineers soon realized that keeping multiple larger electrode meshes stable and in perfect alignment was difficult in mass production. Therefore, Vlad told me, "not many were made."

Today, the technology is in place to manufacture a sturdy, stable, lightweight enclosure for Omega-sized mesh electrodes. The SR-X9000 is the proof.


According to the Stax website, Stax's "major technology advancement is the 'MILER-3' (Multi-Layer-Elect-Rords)—a four-layer fixed electrode combining mesh electrodes and conventional etching electrodes crimped together by thermal diffusion bonding. ... The SR-X9000 diaphragm is made of ultra-thin engineering film that is 20% larger than the previous flagship SR-009S." According to the Woo website, the diaphragm mass has been reduced "to create a lightning-fast reaction speed and more extended high-frequency response."

On the SR-X9000, the Omega's heavy enclosure has been replaced by a lighter, machined-aluminum one: Now the entire well-fashioned, superbly finished, open-backed headphone weighs just 432gm.

SR-X9000 + LTA Z10e: Linear Tube Audio's dramatically useful, natural-sounding Z10e integrated amplifier is specified to make 10Wpc into 8 ohm loudspeakers. From its front-panel headphone jack labeled "HI," the Z10 generates sufficient power for the hard-to-drive, 60 ohm, 83dB/mW HiFiMan Susvara. Through the jack labeled "LO," it makes enough voltage to drive my beloved 300 ohm, 99dB/mW ZMF Vérité closed-backs. These are major accomplishments considering that the Z10e sounds equally superb on every output and costs only $4900 ($5400 with MM phono preamp).


In my world, German viola da gamba player Hille Perl and her American husband, Lee Santana, are about as hip, goodlooking, and creative as people can be. Santana plays lute, theorbo, and baroque guitar. I've spent many a night bathing in the harmonics of their 2004 recording Marin Marais: Pour la Violle et le Théorbe (16/44.1, Deutsche Harmonia Mundi/Qobuz). But it wasn't until I played it with the SR-X9000 that the effects of microphones, mixing, and sound-doctoring became obvious. The new Stax opened up this recording, recovering all the gorgeous tone color while resolving all the sensuous bow-on-string detail.


When I played Stravinsky Conducts Histoire du Soldat Suite (LP, Columbia MS 7093) through the SR-X9000, this stunning recording's dramatic soundstage stayed entirely inside my head. I was a little surprised by that, because the Audeze CRBN electrostatic headphones I auditioned in Gramophone Dreams #56 presented images that extended outside my head, sometimes as much as 18" in front of my face. Nevertheless, the soundspace the Stax generated was full and complete, perfectly mapped, and cram-packed with delectable detail.

I wish you could have heard "The Devil's Dance" from the Histoire du Soldat Suite with the Z10e powering the SR-X9000; the echoing harmonics, the sound of drumhead skins, and an X-ray view of the timpani were on full display. Nothing was blurred or missing. Details behind details inside details. What a pleasure.


When I streamed a live version of Toots & the Maytals performing "Pressure Drop" (Live, 16/44.1, Mango/Tidal), I heard the voice of cool-running Toots Hibbert sounding fresh, alive, and excited to be performing onstage. His body formed a distinct presence inches from his microphone. Headphones do not image like floorspeakers, but what they do better than floorspeakers is put the listener right there, in the space with the performers. While grooving with Toots and his band, my mind opened up and traveled back to those dirty 1970s New York streets and my loft on Crosby Street where I first experienced "Pressure Drop" while listening to Jimmy Cliff's Harder They Come soundtrack. With these new Stax headphones, the sound did not enter my physical body the way it did back then with my Altec 604s powering a big room, but the rockin' philosophical spirit of the song was communicated extremely well. Toots's sincerity and humanity were conspicuous.


This kind of human-poetic feel is not something I've routinely experienced with electrostatic headphones, which typically sound analytical. Powered by the Z10e, the Stax SR-X9000 made Toots's performance sound sunshine-bright and naturally detailed but also relaxed and ganja-colorful. The opposite of analytical.

Another virtue of the LTA Z10e was that it allowed me to compare the new Stax flagship to HiFiMan's venerable Susvara planar-magnetic openbacks without changing amps. What I discovered was, the SR-X9000 and the Susvara are more alike than different. A casual observer might not be able to tell them apart. To my ears, the chief difference was that the Stax played very slightly brighter, more upfront, more distinctly detailed, and a tiny bit more physical. The Stax's upfrontness made the Susvara sound darker and deeper-spaced, more misty-humid than I usually perceive it to be.

With the Woo Audio 3ES: In GD56, I borrowed Woo Audio's 300B-based 3ES electrostatic headphone amplifier/preamplifier to audition Audeze's new CRBN electrostatic headphones. I thought it would be illuminating to use the 3ES with the Stax SR-X9000.

When Toots sings "pressure got the drop on you," the 3ES emphasized the speed and timing of the groove. The strong rhythm'n'beat emphasis came through even stronger playing Toots's hypnotic "Sweet and Dandy." With the 3ES, the Stax diaphragms sounded like they had more muscle behind them. This illusion of greater force made "Monkey Man" jump faster and hold my mind more completely. Compared to the Z10e, the Woo played cooler and dryer, which abetted an illusion of greater resolution.

I used "Buddy & Maria Elena Talking in Apartment" (Down the Line: Rarities, 16/44.1, Geffen/Tidal) to compare the resolving powers of the Z10e to the Woo's 300B. I felt that both amplifiers were excavating equal amounts—but different types—of previously hidden sounds from Holly's space-and-air–filled Manhattan apartment. The Woo better described room volume, ceiling height, and floorplan. The LTA brought more detailed car and street noise in through the window. Both amps let the SR-X9000 make the sound of Maria Elena hanging up the plastic wall phone into a major Wow! moment.

Footnote 1: See Tom Norton's review of the Stax SR-Omega, which cost $3000 in 1995, here.

Footnote 2: STAX International, Room 2101, 21st floor, The L. Plaza, 367-375 Queen's Road, Central—Hong Kong. Tel: +852 2522 6989. Web:


Jack L's picture


Really? Then I had to be a lucky duck!

I used Russian Sovtek ECC83s in my home-brew all-triode classA power amp for 4 years now. Nearly 4 hours a day on my days off every week. Thousand hours working time already. Still sounding soooo gooood!
Never need to replace any tubes !!!


Listening is believing

Jack L

Jack L's picture

....... voltage—a tube that Tim dubbed the 13D16." qtd HR


So how much is the "slightly higher" operation voltage ?

13D16 is not available in the tube market. Per another online audio journal, this tube could be a in-house model created by EAR by testing tons ECC83/12AX7/likes & select some for EAR inhouse rebranding.

Smooooke mirrors ??? Hopefully not that bad !

FYI, the 50-year-plus Telefunken ECC83s I installed in my home-brew phono-preamp (in RIAA phonostage) built 5 years back, are operating at 630V since day one !!!!!!

Still kicking around like nobody's business - sooo good sounding up to this hour ! Please look up the image of this super-compact phono-preamp in my profile logo above. No kidding !

Who said ECC83/12AX7 not so durable ???

Listening is believing

Jack L

SGva's picture

630 Volts? Seriously? 12AX7A's maximum plate voltage, in A1, is rated at 330 volts. That's according to an RCA spec sheet. How in the world are you applying 630 volts?

Jack L's picture


Correction: B+ = 440V after I measured it today as I've not checked it out for a long long while. My memory failed me this time.


Jack L

Jack L's picture


Good question! You are correct as you really know & paid attention to my above post.

Sorry having missing some crucial wordings that confused you, my friend.

So often my fingers move faster than my brain:

It should read: "..are operating at HV power supply B+ = 630V.

Since the ECC83s are working in the RIAA stage with high load resistor so the ECC83 plates are still "operating" at high voltage but still within its rated max plate voltage. High operating voltage is used in order get the max voltage gain from the triodes

Thanks for pointing this up.

Jack L

PeterG's picture

Thanks so much for the Stax review. I especially appreciate the amplifier pairings and comparisons to other A+ headphones. It's the only way to put all these great options in context. I bought a pair of 009S a year ago and I'm absolutely in love with them. So in love that now I absolutely have to trade up... (Not a healthy relationship, haha)

Jonti's picture my own internal monologue on the merits and wonders of the Phono Box/Phono Classic. I've had mine for about 18 months and still have a sense of quiet awe every time I listen to/through it. I'm glad you've also been enjoying the experience.

Incidentally, on the tube-rolling front, I have switched to NOS Mullards, which work a treat by (to my EAR) thickening the syrup and stirring the pot in such a way that the ends and edges of trailing sounds glisten, firing off from a weightier centre. (The stock EAR-stamped tubes were fine, just different: lighter-sounding, I think; I assume Tim would have approved the use of NOS Mullards given his views on the quality of many new tubes doing the rounds.)

Just for the benefit of any readers thinking about rolling those tubes, here's some extra instruction I received from an engineer at EAR Yoshino on how to go about it:

"Remove the top cover by removing four screws on the bottom of the unit.
The jumper plug is located on the left side of smaller power supply circuit board labeled ECC83 and 13D16. The default position for the jumper is 13D16 with standard 13D16 valves fitted. If ECC83 valves are fitted then move the jumper one position to the right in the ECC83. position."

And finally, on the subject of MM/MC carts, I think it's fair to say that the Phono Box really excels with MMs but is capable of giving most MCs a solid platform too. If you still have your review sample, I recommend trying out some of your favourite Moving Magnets for a completely different flavour.

Keep up the fine work!

hemingway's picture

If only... I read only recently they used to manufacture floorstanding speakers. They looked great, if you like vintage midcentury look. Never seen or heard a pair but they were made before I was born. If only these headphones could be turned into floorstanding speakers...

shawnwes's picture

Herb, you're one of the few audio writers I fully trust that they mean what they put down in print. AD was another. I was using the Valab LCR phono stage for the last few years but after upgrading my TT to what for me is an end game component TTW Gem V2 rim drive I felt I needed to up my game in the phono pre area. Based on your poetic waxing (as I'm unable to listen to HQ phono gear w/o a 4 hour drive to Vancouver) I'm now enjoying the Sky 20 and the EAR Phono Classic MM version (w/o volume control). It lets the Dynavector XV-1s just shine through and do its lovely delicate dance through the record groove. Thanks!