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  • Stax
  • 430 Kamitomi, miyoachi - choirums - gun, Saitama Prefecture, Japan T 334
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Equipment[add model]

Stax manufactures or has manufactured the following equipment (click to expand models list):

Dynamic Speakers
Electrostatic Headphones
Electrostatic Speakers
Solid State Amplifiers

General information [contribute]

Stax is a manufacturer of electrostatic headphones. In the past they have manufactured ESL's, solid state amplifiers, CD players and Turntables.

J.M. Willigens (December 3, 2000): Stax ESL were all extremely difficult to drive and even then max sound pressure was always seriously limited. This may be the reason why Stax developed extremely powerful class A transistor super-amps, the 100kg heavy DMA-X1 (300W into 8 Ohm, 600 into 4 Ohm) and the slightly lighter (47kg) mono-amp DMA-X2 (respectively 600 and 1000W into these loads).

While listeners agree that the Stax sound of these ESL's was, as ever with Stax, an enchantment, all agree that high sound levels were not their cup of tee, even driven by a DMA. So an OTL tube amp might drive them beautifully, but even a very powerful Graaf or Silvaweed OTL will encounter some limitations in sound pressure and dynamics.

Christian Steingruber (December 12, 2000): Some Stax speakers were sold in Italy and Greece. There might be still a production line of the F81X and F83X series, but they are probably only available in Japan.

Joerg Baar (July 19, 2001): Electret Solid electrically insulating, or dielectric, material that has acquired a long-lasting electrostatic polarization. Electrets are produced by heating certain dielectric materials to a high temperature and then letting them cool while immersed in a strong electric field. An electret is an analog of a permanent magnet.

A.F. van Werkhooven (September 2001):): Stax has made three dac's; two of then are 'normal' DA convertor's called the DAC-TALLENT and the DAC Talent Battery Powered. The other one is the Stax DAC-X-1-T, a 20Bit/8 times over sampling D/A convertor with vacuum tubes.

The Audio Circuit (October 2, 2010): Special thanks to Howard Popeck, who has provided us with a great amount of information on STAX and its products.

Ray Kallas (February 1, 2016): I have an odd set of Stax Class A DC Mono Block amps: Model DA-X1. Also have a set of ELS-8X speakers. Would love to get more information about them.


STAX - It's a family affair.

This article first appeared in Hifi-Choice 1991.

The Hi-Fi Choice in Japan series continues with Dan Houston and photographer Chris Richardson boarding the bullet train and heading for the home of the electrostatic 'earspeaker'.

The story of Stax is also the story of modern electrostatics - the firm's founder even named it by shortening the word electrostatics. Today Stax is nearly 40 years old and is famous throughout both the audio and recording worlds for its electrostatic headphones. But it also makes floor standing electrostatic loudspeakers, gigantic amplifiers on castors, the Quattro CD player, and a new digital to analogue converter which uses valves in the output stage - the DAC Talent.

Stax is run by a family; the 84 year old founder and chairman Naotake Hayashi, his wife Toyoko, and their son, the company president Takeshi Hayashi.

The current factory was built 20 years ago and has been added to over the years - the end result being a collection of prefabricated units which looks as though someone has just plonked them down on the plot. The factory employs 35 people, mainly assembling components which are supplied by a range of (often local ) firms. A main corridor on the ground floor leads to the spartan offices, a carpeted listening and reception room; workshops full of test equipment and, at the end, an anechoic chamber hung with rolls of acoustically absorbent material. Plain duckboards across bare earth lead off to speaker assembly units, while back in the main building the first and second floors house dust-free rooms for the assembly of headphones.

Heading for the toy room

If the words tawdry, run down or functional spring to mind then one must take heed of Wordsworth's aphorism: 'plain living; high thinking'. And posters around the walls, of musicians like Chick Corea (wearing his SR Sigmas the wrong way round!), confirm the standing of the company. The one room which is far from plain is Naotake Hayashi's office - or toy room as his son refers to it.

At 84 Naotake still puts in a full day's work, striving to develop electrostatic principles ever further. During our visit he was testing his latest invention - a six feet high horn-loaded electrostatic loudspeaker. The new unit was playing with a dedicated transformerless vacuum tube amplifier; the tube being connected directly to the diaphragm. The speaker folds like a screen, with the wide baffles acting as a straight horn to the diaphragm, and will be finished by the autumn. Although the type we listened to was made of wood, eventually the hinged baffles will be made from Coran, a heavy, inert plastic material manufactured by Du Pont.

"We first thought of this 25 years ago," Takeshi told me, "but it was too big and cumbersome and used a round, wooden horn. The new material is expensive but very inert and there is less vibration. The horns can fold so users can adjust the sound. We're thinking of making a smaller one but the problem of a smaller diaphragm is that it would give more coloration and less frequency extension." Even with the prototype it was possible to hear how the system worked with the horn amplifying the sound of the driver without making it too directional or harsh.

The company was founded in 1952, its first product being a cartridge using electrostatic theory to convert vibrations into electronic signals. In the toy room, papers and case files surround the walls, along with examples of the company's products over the years. Books on music therapy confirm Naotake's long held belief that music is essential to good health: "soft but clear sound is important," he told us. A small tool box contains a saw (for fine tuning the horns perhaps) while several industry awards collect dust on the shelves and indescribable boxes with their electronic innards spilling out reflect a hands-on approach to design.

Takeshi takes up the story: "After the second world war my father worked in Shanghai as a recording engineer with the Chinese Recording Company. He was always interested in systems which would deliver the best sound quality and he started researching electrostatic theory.

"Electrostatics were invented by a German in 1880, but the materials for the diaphragm were never good enough for quality sound reproduction. Chemical technology had improved during the war and there were better plastics available - even though we now believe purity of sound is better with just the bare metal. Our first products were the Monaural Radio Frequency Condenser Phono Cartridge and an integrated tonearm designed especially for use with the cartridge.

"In 1956 we were still only a cartridge manufacturer and my father patented a design of cartridge with a rotating stylus. Because you rotated the stylus every time you played a record we could use a softer sapphire tip. Another feature of the stylus was its extremely light tracking weight - about a gram - which gave better tracking performance at a time when other styli were tracking at between 10 and 20 grams.

Stax first came to prominence with its ear speakers which made their debut at the Tokyo Audio Fair in 1959. Takeshi remembers the occasion even though he was still a boy: "I was at junior high school but was already starting to help my father where I could," he said.

The ear speaker

The original headphone was the SR1 ; it was the first electrostatic headphone in the world and set a pattern for the types that were to follow, coming complete with its own energiser unit. Gradually the headphone business took over, even though Stax continued making cartridges and tonearms, finally winding up production in 1977 when the company's last electret direct pickup cartridge was made. "We'd still like to make a phono cartridge," Takeshi said, "but the problem is finding the time."

Headphones now account for 70 per cent of the company's business although as Takeshi points out, products such as the loudspeakers and DACs are changing the ratio slightly says. The early headphones were soon followed by Stax's first full range floorstanding electrostatic loudspeaker, the ESS 3A , launched in 1960. The main reason for developing electrostatic products was to avoid the problems of magnetic hysterisis, something Takeshi views as one of the major disadvantages of traditional dynamic loudspeakers.

There are now three models of loudspeaker: the nearly two metre high elegantly proportioned ELS-F83, the shorter and slightly wider ELS-F81 and the colossal ELS 8X. The latter is also available as the ELS-8X BB (for battery box). The DC battery supply gives 4,000 volts to polarise the massive diaphragm; it's basically similar to a Stax headphone but with the polarising energy multiplied to compensate for its size. And with the powerful batteries lying on the floor next to the loudspeakers it's not the sort of thing you'd want with children crawling around, as Takeshi admitted.

"Electrostatic energy is getting force from plus and minus signals with a single diaphragm between electrodes," he explained, "if we apply DC voltage to the entire diaphragm and put a high voltage through the plus and minus sides the diaphragm is pulled by the opposites and pushed by the same polarity - that's the basic principle. But we need to polarise the central diaphragm and by using a powerful DC current from the batteries we can eliminate the noise, which is present from the rectifiers in AC systems, and so reduce the impedance factors.

"It's exactly the same with the ear-speakers. The regular system uses a 230 volt power supply and the professional series uses 580 volts - they have battery packs for DC and better sound." This is why the ear-speakers need an adaptor (AC or DC) which raises the signal voltage from your amplifier to cater for the polarising energy needed by the diaphragm.

Takeshi joined the company in 1972 after reading Mechanical Engineering and Industrial Design at Sofia university in Tokyo and a short spell with the research and development team at Harman Kardon - in Long Island, New York. He worked on Stax's first stereo Class A DC power amplifier, the DA-300, a 150 watt per channel monster which was to provide the pattern for subsequent Stax amplifiers. "The Mark Levinson company used it as its reference power amplifier until it had finished its own," he told me with some pride.

A glowing reference

Alongside the DA-300 sit a variety of valve amplifiers, built by Naotake in the Fifties for use in the listening room. Indeed valves are still very much in favour at Stax. The company's first digital to analogue processor, the DAC-X1T, uses a dual triode valve in the output stage, as does the new slim and compact version - the DAC Talent, which also uses a new American made "glitchless'" chip to eliminate the need for de-glitching circuitry which degrades sound quality.

Valves are also in evidence in the SRMTI ear speaker energiser. Valves deliver superlative sound according to Takeshi, who believes that the simplicity of valve circuitry along with the perceived smoother or faster passage of electrons through a valve have kept it very much in the audiophile domain in spite of the greater availability, reliability and design attractions of the transistor.

Powering up

The side-by-side development of both electrostatic loudspeakers and amplifiers led to one of the most powerful amplifiers ever made. In 1987 Takeshi unveiled his DMA-X1, an FET output monoblok that weighed a massive 101 kilograms and which could push 1,000 watts into a one ohm load. As Takeshi describes it, it was more like the power supply for a welding machine! When you consider two were needed for stereo it makes sense that the amplifier was fitted with castors.

Last year another power amplifier arrived. The DMA-X2 is a slightly smaller version, weighing in at a mere 47Kg, and with non negative feedback and Class A output stages. "The power supply is A/B which reduces the problem of heat generation. It is balanced from input to output and is a traditional BTL (balanced transformer less) design," said Takeshi. If all this implies that Stax is not primarily a headphone manufacturer then that is also what we discovered. However, the company is probably still best known for its electrostatic 'ear speakers'.

1977 saw the launch of the SR Sigma where the electrostatic diaphragms were angled slightly in front of the ear to make the listener believe he is hearing sound from in front. In 1982 the Lamda Pro and Lamda Signature followed the same design philosophy and incorporated high quality PCOCC cable and a thinner membrane "for golden ears" as Takeshi describes discerning audiophiles.

Going digital

But by the mid Eighties Stax was heavily into digital electronics, releasing its Quattro CD player in 1986. The Quattro uses a Sanyo Fisher drive system and Stax designed electronics in the digital to analogue conversion process. The 18-bit CD player was followed by the DACs which also use multi (20) bit technology. Takeshi doesn't rate bitstream as highly as some: "We have measured the new Philips one bit chip and we can see that noise levels are greater than with multi bit systems," he said showing me graphs to prove his point.

Takeshi himself favours the analogue medium for its higher frequency range and more lifelike qualities: "The problem with digital formats for high-end people (audiophiles) is that a higher bit or higher sampling frequency is needed. We don't just listen to music with our ears - we can also feel some frequencies with maybe our face or stomach. CD is still in its infancy and of course even four bit technology would be popular with most people. Denon has announced that it will making a higher density CD which will carry higher frequency sampling - that could be good for audiophiles."

One can see that the making of Stax products is both exacting and painstaking. Takeshi said he spends hours every night listening and relistening to products with a view to improving them. And while the factory may not be as plush and clinical as some of the Japanese workplaces we visited, products are all hand-assembled and rigorously tested before leaving for Germany or the States, or any other of Stax's 20 marketplaces.

Stax engineers don clean clothing and masks to work in a dust free environment while assembling the delicate diaphragms of the ear-speakers and matching a left and right pair for efficiency.

Even though it's not a noisy factory Takeshi says he wants to extend it to incorporate a small concert hall and proper listening room where the engineers can play live music before listening to recordings on quarter inch tape. Whether this will be on the scale of the Nakamichi hall we visited last month remains to be seen, but if the company's previous exploits are anything to go by then you can rest assured that it will be more than a little out of the ordinary.

"Reprinted, with permission, from Hifi-Choice, 1991 Copyright 1991 by Hifi Choice. All rights reserved."

Howard Popeck (September 25, 2010) The following information was taken from Simply Stax:

A brief history of STAX Tonearms

STAX tonearms were in production from 1952 to 1981. There were 5 principle designs, plus a series of derivatives (carbon fibre tubes, extra-length tubes, etc) giving a total of 18 models. It seems that all of these were uni-pivot models rather than, for example, the SME knife-edge bearing types.

With the later models, especially the UA-7, the construction and finish were superb. The UA-7 and derivatives are not particularly rare and for non-carbon-fibre versions, attract reasonable but not excessive prices.

We've never been particularly attracted to the sound of uni-pivot designs in general, and the STAX is no exception. While the mid-range on most well-engineered uni-pivots is usually exemplary (STAX included), we find such designs somewhat lacking at both ends of the frequency spectrum. STAX tonearms aren't particularly easy to use, if you want a turntable lid in place, due to the fact that they used lengthy rear stubs with the counterweights someway back from the pivot point. From memory, we don't think we were particularly successful mounting these on suspended decks either, preferring to mount the STAX on solid decks such as JBE, Trio, Micro Seiki and so on.

Having said this, it was a very successful match on some of the Michell Engineering turntables and that fine company still produce STAX UA-7 arm boards for all and any previous Michell decks.

It's worth mentioning that some of the very early tonearms (1950's) are quite eccentric in that they are designed exclusively for early STAX cartridges i.e. some of these arms do not have detachable headshells and only a STAX cartridge can be fitted. These cartridges are extremely rare.

A brief history of STAX CD Players

Only two models were produced. The Quattro 1 was built in 1986 and as far as we know, was never imported into the UK. The one that was imported though, and was the subject of the Hi-Fi News review was the Quattro 2. It was in production in 1988. We actually have one. In fact, the very one that was reviewed by Hi-Fi News. It's not for sale, and that's partly due to it not working very well currently.

STAX said at the time: If you're a listener who's felt that something was missing from CD sound, if you believe that the highest audio fidelity can still be best achieved by a quality turntable and phono cartridge, we would like you to audition the STAX Quattro CD player. We think its consummate musicality and its unerring fidelity to the original source signal will convince you that digital audio has truly reached maturity

We agree.

A brief history of STAX loudspeakers

We love the sound of these speakers, but why? They have no real bass slam, they are quite directional, they don't go very loud, visually they aren't very attractive and their dynamic capability is limited. Sounds familiar? These are comments similar to those made about the original Quad electrostatic speaker, the legendary ELS-57. In many ways, the STAX loudspeakers are not dissimilar, although on balance, we found the sound of the STAX units to be more to our taste. However, owning a pair of STAX loudspeakers, let alone finding a pair is not without challenges. And then having found a working pair, you'll need serious amplification to drive them as their efficiency is so low.

STAX electrostatic loudspeakers, now sadly out of production for many years, operate on the same principle as their electrostatic Earspeakers. That's why it was possible for the STAX loudspeakers to obtain such incredibly rich and detailed reproduction from such a thin panel.

The STAX push-pull electrostatic drive system has extremely low mass and is driven across the entire diaphragm surface, so it suffers from none of the cone break-up problems or distortions that plague conventional speaker systems employing magnets and voice coils.

Top-end frequency response, mid-range transient response and phase response are, from memory, simply unbeatable, although it has to be said that appropriately driven, Apogee Scintilla speakers can give the STAX's stiff competition in these areas. Some of the more advanced Martin Logan speakers get close to reproducing the characteristically airy STAX loudspeaker sound, with greater volume and slam. Close, but not exactly there.

Of course speaker technology moves forward, although somewhat more slowly than source technology and it's logical to assume that sooner or later, all the attributes of the STAX loudspeakers will be achieved elsewhere. You could consider stacked Quad ELS-57's as a very worthy alternative in the interim.

STAX ELS speaker systems are, low efficiency notwithstanding, are easy to use. You merely connect the speaker leads from the power amp to the speaker terminals, and plug the speakers systems into a mains outlet.

The ELS-F81X impedance is around 3 ohms and the efficiency is 76dB. The ELS-F83X has an impedance of 4 ohms and an efficiency of 80db. This means you need a powerful, robust amplifier able to happily work into low impedance loads and with a true 100 watts RMS per channel "minimum" if you want to generate realistic transient responses.

The state-of-the-art ELS-8X and ELS-8XBB loudspeakers have a far more comfortable 8 ohm load. We are unable currently to clarify the efficiency on these two models.

A brief history of STAX power amplifiers

Once again we have to fall back on reputation here rather than hard facts for the 7 models in the series. These units are VERY sought after.

The DMA-X2 is considered by some to people to be the most musically involving power amp of all time. It certainly was mighty, at 600 watts Pure Class A RMS into 8 ohms. 47kg too. But muscle wasn't really what STAX were about here. Clarity, delicacy, transparency were the primary design goals. Do take a look at the photo of the DMA-X1. Yes, those really are castor wheels on the amplifier. It really is that heavy. Currently we are searching for factual information on this and the other 6 models.

Expect to spend serious money for any STAX power amp in working order. Even so, we really do feel a high recommendation based on reputation is necessary. It's worth patience to track them down, however, as you'll see on the pages dedicated to each of the models, do please read our BUYING ADVICE comments. Only some models have externally switchable voltage. Some models were never built with a UK voltage option. Also, servicing can be expensive if the model has to be returned to Japan.

Regarding servicing, the good news is that it seems that STAX/Japan archive all the plans for all the models and short of a complete meltdown, can internally re-build any boards and replace any internal parts. They don't get involved in cosmetic restoration though

A brief history of STAX preamplifiers

Only 6 models were released to the public. For simplicity, they can be divided into 2 separate types, as follows:

  1. The preamps that have built-in sockets for STAX electrostatic Earspeakers. These are the SR-12S and the SR-14S. We own examples of both of these and no, they aren't for sale. Usefully, these two models have built-in equalisation for the unique STAX pickup cartridge generator mechanisms. We're not sure though if these inputs match all or any of the early STAX pickup cartridges.
  2. The preamps that don't have sockets for Earspeakers. These are the CA-X, CA-X pro, CA-Y and CA-Z.. We own a CA-Z.

Production was relatively short-lived. On the face of it, the preamps should be used with the matching STAX power amps. However, neither the makers nor UK distributor insisted on this. We've partnered our 3 examples with non-STAX power amps and even Meridian M1 active speakers. In every instance we've been delighted with the sound.

The designers and makers managed to achieve that elusive and highly attractive combination of valve-like openness with solid-state dynamics and tightness. In short, they achieved the STAX earspeaker hallmarks of details and transparency, but through stand-alone amplifiers.

Given the pretty low prices for all of the models, except the CA-X pro, which seems to attract high prices (£1,500 or more) and the superb sound quality, we really do feel a high recommendation is necessary. It's worth patience to track them down, HOWEVER, as you'll see on the pages dedicated to each of the 6 models, do please read our BUYING ADVICE comments. Only some models have externally switchable voltage. Some models were never built with a UK voltage option. Also, servicing can be expensive, if the model has to be returned to Japan.

Regarding servicing, the good news is that it seems that STAX/Japan archived all the plans for all the models and, short of a complete meltdown, can internally re-build any boards and replace any internal parts. They don't get involved in cosmetic restoration though.

A brief history of STAX Diffuse Field Equalisers

There is quite a lot of confusion regarding the thinking behind, and application of the STAX Diffuse Field Equalisers. A common misconception is that they can/should only be used with the SR-Lambda Professional Earspeakers. This isn't entirely correct. What follows here is our best attempt to sort out the reality of the situation.

The ED-5 Equaliser is for use with the SR-5 series of Earspeakers. The most well known of that series is the SR-5N and the black version of this, the SR-5NB.

The ED-1 Signature is for use with the SR-Lambda Signature. The Lambda Signature is a Normal Bias Earspeaker and uses a different connection to the PRO-bias model.

The ED-1 Monitor is designed for the SR-Lambda Professional (PRO-bias) Earspeakers.

The SRM-Monitor is in fact the guts of the SRM-1 Mk2 in a new case with three Earspeaker outputs. The equaliser curve seems built into all three of the output terminals, with a front panel switch to engage or disengage the equaliser curve. As far as we can judge, it can accept both normal-bias and PRO-bias Earspeakers. However it seems that it was optimised for use with the Lambda Professional Earspeakers.

As and when we get more information, and providing it's reliable, well post it here. Thank you.

A brief history of STAX electrostatic cartridges

And yes, we really mean brief. That's because despite vigilant searching by us, no worthwhile information on STAX phono cartridges can be found, so far. Having said this, it's a curious and somewhat interesting fact that the reputation for these very rare beasts is legendary.

Production of various very innovative models was between 1952 (the CP series) intermittently through to 1979 for the CP-Y/Type 2. The STAX cartridges need a STAX equaliser to work correctly. This means that you can't plug it directly into the phono stage of a pre-amp, other than the rare STAX SRA-14S preamp, which had an optional cartridge EQ module.

We're not taking about head amps here or step-up devices. The STAX cartridge equaliser is a specific unit designed to convert the cartridge's electrostatically-generated output into an analogue form. Also, as far as we know, the various equalisers are not interchangeable with the various cartridges, which means that you should only buy a STAX cartridge when partnered with its specific matching STAX cartridge equaliser.

Speaking to people who have heard the CP-Y (or, perhaps what they thought was the CP-Y), many years ago, the sound quality had a transient attack, bass tightness and definition and an airiness/transparency that had no equal. But, and it's a big but, indications are that their reliability was questionable and the cartridge was temperamental and temperature-sensitive. Nevertheless, for people, in the know, it doesn't seem to dent enthusiasm.

We have no direct experience of these cartridges. We saw a CP-X for sale earlier this year on the Audiogon website, for sale in Switzerland. We dithered. And when we decided, it had been sold for $1,000.

Valuable comments from a STAX Electrostatic cartridge owner

I once owned a Garrard 301 turntable with a Stax tonearm and one of these condenser pickups. I don't remember the names, but the pickup needed a two-tube box for demodulating the signal from the pickup.

As much as I remember there was a RF-frequency oscillator inside, the condenser inside the cartridge modulated the RF-frequency and was then demodulated like in a FM radio, a further stage made the RIAA equalisation and step-up to the preamp. There were two different oscillators, one for each channel, and the system suffered from occasionally locking in on the same frequency of these two oscillators. The result was a mono output and some distortions. Also there occurred a difference tone between these two RF-oscillators, that disturbed the reproduction, but for the few moments when everything worked fine, the reproduction was such outstanding in comparison to the usual MC-cartridges, that I ran into deep depression when the system made it's noises.

From a today's view the problem was a too bad channel separation inside the tonarm, where the internal wirering is not shielded. You would need something like a double tube tonearm and a demodulation in two different boxes. Or, with today's micro-techniques, it should be possible to have the demodulation inside the cartridge already, to have no RF conducted for longer distances.

28/10/04 Our thanks to Mr Helmut Brinkmann from Germany for this.

Refurbishing & modifications[contribute]

Joerg Baar (February 2002): England Repair department

Germany Repair department

Germany dealer

John R. Broskie (from GlassWare Audio Design Software) (June 2002): I have built several tube-based OTL circuits for my Stax SR-Lambda Pro headphones and I put out a free webzine that has covered driving ES headphones in at least two issues. Follow these links to see what I have published:

External links

Stax Electrostatic headphones
Stax Unofficial Page

Forum topics on Stax

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