Headphone amping on the highest level
August used to be just like you and me: searching for the best possible sound with the best possible and often quite expensive hi-fi gear, the goal constantly escaping the stretching hands. Over the period of twenty years or so he had such loudspeakers as Acapella Violin, Sonus Faber Quarneri, Infinity Kappa, Audio Physic Medea, Magnepan 1.6, Omega Sigma, and Audiostatic ES300 etc. powered by such amplifiers as Mark Levinson 28, 23 and 332, Jadis JA-30, JA-80 and JA-845, Cello Etude/Encore 50, Pass Labs X-600, Electrocompaniet AW-250, Lavardin IT and so and so forth. This is a story of how August eventually gave up everything, turned to a headphone hobbyist, and became a tube specialist of the highest calibre.
It was late 1990s/early 2000 when August realized that, intoxicated by effective marketing or misguided by things more internal to him, he had been roaming around in the hifi-wonderland for decades making acquisitions based on less important factors such as the outlooks of the gear. "All those loudspeakers, amplifiers, cd-players etc. had served other purposes in my life than music listening. I upgraded the system simply for the sake of upgrading it, not because of music's sake. That made many dealers happy, but didn't make me happy", August now confesses.
During the transition period August got interested in the famous American website for headphone nuts, head-fi.org. He begun to follow what some of the world's leading headphone enthusiasts had to say about their experiences. And the rest, as they say, is history.
Determined to change the course, August gradually gave up his hifi-system, and decided to narrow down his music listening to headphones only. In case that he is hit by the desire to listen to loudspeakers rather than his headpones, he kept a pair of Oper Audio M-15 MkII horn loudspeakers, sensitive enough to be driven with his small power headphone amps. His current loudspeakers are 98dB sensitive Kochel K-300 SDS.
Close to the source
August classifies headphone users into three categories. Ordinary headphone listeners seek relatively inexpensive headphone systems, since headphone listening is often the only practical alternative in their case. Then there are people who, convinced that their fashionable mobile life-style requires it, use headphones more freely eg. in the street.
Highend headphone hobbyists, however, need not, for circumstantial reasons, settle for headphone listening solely, and often own a quality hi-fi system as well. Within this group there are those whom August calls "extremists", and into which group, without false pride, he classifies himself too. These are people who are willing to sacrifice a substantial amount of money but especially time and other resources in order to put together phenomenal headphone systems.
Common to the extremists is the motivation they share: "to be as close as imaginably possible to the source". This goal is always the same, but gets different interpretations: "Some aim at being sonically as close as possible with the master tape, others want to get in an intimate connection with the soulfulness of the music. But whichever the specific goal is, it calls for the best headphones and headphone amps there are.", August declares.
Which headphones are the best?
Dynamic, magnestostatic and electrostatic headphones all have their devoted friends, and their relative betterness is, of course, heatedly debated in dedicated forums. If August is asked, magnetostatic headphones are almost but not quite equal in quality to electrostatic headphones. According to August, the most wanted magnetostatic headphone, among the enthusiasts, is currently Audeze LCD-2 or LCD-3. He too once had one. Hifiman HE-6 is a good one too. But "magnetostatics sound best when connected, not to the amp's headphone output, but to speaker terminals!"
His feeling is that the popularity of dynamic headphones is currently growing also among more advanced headphone hobbyists. The supply side has reacted by launching some high quality dynamic headphones such as Sennheiser HD-800 and Bayerdynamic T-1. But: "Neither has reached the sound quality of the legendary Sony R-10 from the 1980s. The high price of the R-10, 4000 USD, didn't feed the demand at the time. Now the same headphones sell for 6000 USD."
The most famous electrostatic headphone is Sennheiser Orpheus, the HE-90 headphones together with the HEV-90 amplifier. Only 300 were ever made, and August too is a former owner. The asking price for used Sennheiser Orpheus is somewhere between 25000 and 30000 euros!
Just like with the R-10, the sound quality of the Sennheiser Orpheus is unsurpassed. "The only real threat comes by the electrostatic specialist STAX whose 5000 euro SR-009 headphones are absolutely musical, in particular when listened through quality electrostatic headphone amps such as STAX SRM-600, HEAD-AMP Blue Hawai/Aristeus or Wooaudio WES", August tells me.
It comes as no surprise, then, that August's current headphones are the newly released STAX SR-009. August spent five years with the Sennheiser Orpheus combo, and "it was like drinking strawberry juice everyday. The STAX SR-009 tastes like crystal clear water in a mountain stream. The question is which one would one want to choose in the long run?" August is convinced that the sound from a headphone cannot become much better than this. "The sense of presence is simply amazing! And the SR-009 is not choosy about music genre. Everything goes, more so than any other headphone I've tried."
And he certainly has. Before the SR-009 and Sennheiser Orpheus August has owned Sennheiser HD-800, AKG 702, AKG K-1000, Bayerdynamic 880, Bayerdynamic T-1, Grado PS-1000, Grado GS-1000, Grado RS-1, Grado RS-2, IGrado, Stax Lambda pro, Stax Sigma, Stax Omega 007, Audeze LCD-2 rev2, Ultrasone 8, Ultrasone 10, Hifiman 5LE, and Hifiman 5. He used to keep more than one headphones at the same time, but gave up the practice as "distancing" him from music. At the bottom is August's comments on some headpnone models that he's tried.
When I first went to meet August he still had his Sennheiser HD-800. With a tailor-made amplifier, they sounded absolutely fabulous to my amateur ears. Second time I heard the STAX combo and felt that the sound was a tad more sophisticated and universal. But when I recently contacted him the STAX's were gone, Sennheiser HD-800 made a comeback, and August had begun to wait for the new edition of Sennheiser Orpheus headphones, which some rumours say is coming.
The art of headphone amplification
August drove the SR-009 with STAX SRM-600. "The SR-009 is less sensitive to amplification than eg. the STAX Omega", he says, "The quality of the DAC is a bigger issue". His current DAC is Audio Research DAC 8, and before that Audio-gd DAC, Ayre QB-9, and Cambridge Audio DacMagic.
But headphone amps are the salt of headphone hobbying as least as much as headphones are, and August will definitely keep on making his experiments with various amplifiers. Tube amplifiers especially because they are the best, and headphones enable hearing subtle sonic qualities of the tubes used. The only exception that August accepts is power hungry magnetostatic headphones that may require a solid state amp. In fact, he himself once run his magnetostatic headphones with his Krell mono blocks.
When August decided to go his "own path" in audio he started to order "custom made" headphone amplifiers that would respect the tried principles and solutions of the first generation of tube amplifiers. Alex Ederer from Austria became his court producer. Ederer has been able to supply August with several "dream headphone amplifiers" in a manner that has helped August to regain his enthusiasm for audio again.
Tubes definitely matter
For August the most favoured output tubes in headphone amplifiers ought to be small power triodes with a minimum number of parts such as 2A3, 45, PX4, 300B or alternatively slightly more exotic V70D, T-40, T-55, 811, and 812. For him by far the best sounding combination has so far been the one, in which the "world's best" input tube, the Cunningham 226 welcomes the signal, the power tube is the RCA 245, and the rectifier Arcturus 80, all rare old tube types.
The sound of this 245 amplifier is reportedly superbly immaterial. Unlike with other tube amps August has tried, there is a beautiful continuum between the notes; the stream of notes is never interrupted. With the 245 all instruments are well placed in the soundstage, and "The sound can be so realistic and musical that it gives goose bumps."
Serious hobbyists prefer old NOS tubes, because they often sound the best and are most durable. Particularly sought after are so called Globe tubes ("globe" refers to the shape of the bottle) from the 1930s, in which all parts are so fixed to the tube socket, and the bottle itself is free from detrimental vibrations. The Globe tubes are for headphone audiophiles what vintage wines are for oenologists.
It took some time before August found the ideal tube combination. He begun with an OTL (output-transformerless) 6AS7 headphone amp by Ederer. "It didin't have much power but suited to my sensitive headphones at the time. The sound was slightly dirty and scruffy, and the stereo image not entirely stable, but all in all quite natural and musical sounding".
Next in order was the famous Siemens F2a. The amp was absolutely silent and distortionless, which is utmost important in headphone listening. It sounded dynamic and detailed too. But still August felt that the sound was somehow too thick and too spacious for headphones, missing a real depth image. The sound was a bit uptight too, he says. "Knowing what I know today I'd say that the F2a is not the most ideal output tube for a headphone amp."
In constrast, August regards the 6C33 as a fabulous tube for a headphone amp in able hands. It has enough power even for magnetostatic headphones. It's not noisy. The sound opens up into all dimensions, but the soundstage remains well-structured and stable. The tube may give an impression of being soft-sounding and half-way coloured but sounds in fact quite neutral with no disturbing frequency wrinkles. Very musical.
The 6C33 amplifier that August once had was, however, an OTL amplifier. "No matter how good OTL amps sound they always give me the feeling that tubes love an output transformer. With an output transformer the sound is more spontaneous, more rhytmical. The downside is that a transformer can add noise and hum to the sound. Moreover, each tube demands a right transformer."
What about the 2A3, 45, and 300B, the other directly heated triodes that audiophiles use to drive their sensitive loudspeakers? August has tried the 2A3 with GZ32/6SL7, and the 45 with GZ34/5U4G. He currently owns the rare Moth Audio 2A3, and according to August it is a very high quality headphone amplifier indeed. It has a same type of sound than the Ederer 245 but is more controlled, the soundstage isn't quite as extended, and most importantly, it doesn't possess the same transparency. The 245 is tremendously transparent tube, and I don't think 2A3 or 45 can compete with it in this respect. Not even if the 2A3 was the legendary RCA coke bottle. The Globe tubes are in their own league."
Despite his slight reservations toward OTL amps August has recently acquired Ederer 300B OTL headphone amp. 300B OTL is a rare beast in the audioland especially with the 6SL7 driver, instead of 6SN7. The amp is not making any hum, and is built inside of an old Sparton radio from the 1930s.
Apart from the 300B OTL system and the Benchmark DAC1/Moth 2A3 SET combo August has a "digital" system for his Sennheiser HD-800: the signal is taken from the iPod dock and handed over to Aberdeen modified TACT T-2 amp, also functioning as a DAC.
August takes it for granted that old tube manufacturers had their own "house sound", which characterizes all their tubes. For example, "RCAs are open and neutral, Ken-Reds detailed and dark sounding, Tung-Sols soft and musical, Raytheons soft but still neutral, United Electronics analytical and musical, Philips Holland soft, musical and accurate at the same time. And so on."
In retrospection, August has often chosen either NOS RCA or Ken-Red as the rectifier tube, NOS RCA as the output tube, and Philips Holland NOS, rather than Siemens for instance, as the input tube. "But there are so many possibilities and many different combinations can satisfy even the most demanding needs."
One has to be careful though since the production of many NOS tubes was licensed. An experienced hobbyist recognizes the tubes from their construction, and from such expert terms as "short-long plate", "halo-getter / d-getter", "double support", "piched-ribbed plate" etc. Tubes also have code numbers that reveal their date of production and the factory.
Another thing is that rectifier tubes, in August's experience, differ from output tubes in that even a cheap Chinese rectifiers can sometimes yield better results than NOS tubed. "By today I have failed to hear a good-sounding mesh plate rectifier tube in any systems. For example, the old Telefunken mesh plate rectifier tube AZ12 sounded worse with my F2a than a new Chinese metal plate rectifier tube."
While talking about NOS tubes and other details regarding tubed headphone amps, August frequently refers to the "good old days" by which he means times before the mass-market oriented transistor and digital era. This personal "back to past" movement has lead August "back to basics" in other fields of life as well. The process has been beneficial not only aurally but also mentally. He has grasped that he can live without an internet-connection at home, without a car - August is a heavy cyclist, without a mobilephone and other modern 'delights'. But because of this downshifting he feels he has grown as a hifi hobbyist.
August's comments on selected headphones:
Sennheiser Orpheus (HE-90 & HEV-90): A big euphoric sound, musical but not entirely neutral.
Sennheiser HD-800: A spacious hi-fi type of sound, can be a little strained in the treble; requires a tube amplifer to sound the best.
AKG K-702: Similar to the HD-800, but overall a step down.
AKG K-1000: Sounds like two loudspeakers on both sides of the head. Needs a powerful amplifier.
Bayerdynamic 880: Quite basic headphones.
Bayerdynamic T-1: Quite good sounding, overall not as good as Sennheiser HD-800, but can be equally or even more musical sounding.
Grado PS-1000: Almost a perfect sound but the listener must meditatively concentrate on the sound.
Grado GS-1000: Not too different from the HD-800 but the sound lacks a taste, which is why some regard it better than the HD-800.
Grado RS-1: Like the GS-1000 but with a more confined soundstage.
Grado RS-2: Warmer sounding than the RS-1, otherwise no big difference.
IGrado: The best iPod headphone.
Stax Lambda pro: A precision tool for an industrial use eg. for spotting problems in car engines.
Stax Sigma: Similar to the AKG K-1000, like two sealed loudspeakers very close to the ears.
Stax Omega: A warm electrostatic sound, but perhaps too introverted, an ideal choice for an intellectual listener.
Stax SR-009: The best headphones ever made.
Audeze LCD-2 Rev1: A warm sound that stays close to the head. Many love the retro looks but all in all not my favourate.
Ultrasone 8: Rhythmical headphones for yuppies and lovers of reggae-rasta music.
Ultrasone 10: Perhaps the lousiest headphones ever made for a price of 2000 euros. Probably hearing problems after one year of use.
Hifiman 5LE: Able headphones from China but this model still needs a few years of perfection.
Hifiman 5: These wooden Chinese headphones sound as if the treble and the bass came from two different headphones.
Hifiman HE-6: The best Hifiman headphone so far, very dynamic, an informative bass but leaves the midrange and music a little distant.