Air tight atm-300r power amplifier stereophile.com hernia discal lumbar tratamiento

To audio designers in Japan and elsewhere, the single-ended, 300B-tubed amplifier is like a haiku: an art form defined by both its prescribed limitations and the potential such restraint offers for artistic expression. Here, the only hard-and-fast rule is a simple one: output devices are limited to one 300B directly heated triode tube per channel. From there, it’s a blank slate escoliosis lumbar dextroconvexa: Do you want AC or DC on the output-tube heaters? Tube or solid-state rectification? Low or high gain? Fixed or cathode bias? New parts, vintage parts, or a mix of both? Triode or pentode tubes as drivers? Capacitors or transformers—or nothing at all—between the plates of the driver tubes and the grids of the output tubes?


I suppose you could even drive your 300Bs with transistors, power the amp with an outboard switch-mode supply, add user-adjustable negative feedback that you can control from your telephone, or build it into a carbon-fiber box topped with ostrich leather—all as unthinkable as making a martini with vodka instead of gin.

I’ve never heard a single-ended 300B amp that I disliked. That said, these days my favorite examples are the ones whose sound steers clear of the excessive sweetness and thickness that some people associate with the genre. Such preconceptions are not groundless: In the mid-1990s, when I tried my first single-ended 300B amp, a Cary 300SEI integrated, the trend among manufacturers and DIY hobbyists was toward passive parts and circuit designs known for compounding rather than offsetting the 300B tube’s inherent warmth (footnote 1). In the 1990s, at least in the US, it was difficult to find a single-ended 300B amplifier that sounded as clear and as musically precise—let alone as emotionally compelling—as the Air Tight ATM-300R. But I’m getting ahead of myself . . .

The ATM-300R ($16,995 with Electro-Harmonix 300B output tubes, $15,995 without) is the latest incarnation of a design that made its commercial debut in 1999, as the ATM-300—then as now, a single-ended amplifier that uses one 300B directly heated triode per channel to produce 8Wpc. The third product in this lineage—Air Tight’s second single-ended 300B amp, a limited-edition product called the ATM-300 Anniversary, was issued in 2016—the ATM-300R improves on its forebears in various ways. Perhaps the most significant of these is the change to a hand-wound, paper-wrapped choke coil for the power supply, in tandem with a hand-wound, paper-wrapped mains transformer—both designed and made in-house. According to Air Tight’s Yutaka "Jack" Miura, son of company founder Atsushi Miura, the new iron results not only in better sound but in slightly higher output: 9Wpc for the 100V version sold in Japan. (For the 120V US version Air Tight retains the 8Wpc rating, apparently motivated by prudence.) Jack Miura also points to the new model’s redesigned power supply, and its use of a brand-new output-transformer design from Japanese transformer specialists Tamura.

One thing the first ATM-300 had that the ATM-300R lacks: a switch for selecting between zero negative feedback and 3 or 6dB of same. That said, the omission sets the stage for something more interesting: The estenosis espinal lumbar ATM-300R has a fixed (unspecified) amount of feedback, yet in each channel, that loop’s output tap is on the primary side of the output transformer, not the secondary. As Jack Miura explained in an e-mail, "Taking NFB from the primary side . . . was used on very old amplifiers such as Western Electric, but not on recent amplifiers." He described the drawback of doing so as the need for a transformer capable of very stable performance—that and the hernia lumbar sintomas fact that primary-side feedback doesn’t produce overall signal/noise specs as impressive as those associated with the traditional approach. But Miura said that Air Tight’s approach "opens-up" and enlarges the soundstage, and offers "crystal clear highs while keeping rich mids and tight bass, unlike the ‘narrow shoulder’ [sound] (this is how my father describes typical 300B tube amplifiers with wobbling bass sound and no sparkling highs)."

Other design distinctions of the ATM-300R: It’s a three-stage design, using 12AU7 and 12BH7 dual-triode tubes—one each per channel—as voltage-gain stages and drivers, respectively. The high-voltage rail is rectified by a single 5U4BG two-part diode tube, supplemented with a slow-start circuit to prolong tube life. And the ATM-300R is an auto-bias (aka cathode-bias) design; an illuminated bias meter on the amp’s front panel is intended not to aid in calibration but to provide confirmation that the 300Bs are operating within their intended range. The ATM-300R was designed by Y. Hayashiguchi and K. Hamada under the direction of Atsushi Miura.

Like all other Air Tight amps, the ATM-300R is built into an enclosure made mostly of bent and welded steel, to which a machined-aluminum front panel is attached with hidden fasteners. Inside, running nearly escoliosis fotos the amp’s full width, is a solid-copper plate to which the signal tubes are fastened, and that serves as a signal ground plane. Except for a small, square circuit board to which some power-supply capacitors are fastened, the ATM-300R is entirely hand-wired, point to point—impeccably done. Insofar as I could tell, all component parts are contemporary, and include Sprague capacitors, Dale wire-wound resistors, and Alps potentiometers. With its dark-gray enamel finish and that unabashedly cool-looking bias meter, the very solid Air Tight amp—at 54 lb, it’s far heavier than its 16.9" by 10.8" footprint had led me to expect—was one of the most attractive amplifiers I’ve ever had in my home.

Apart from its pushbutton power switch, the ATM-300R has only three user controls: separate Attenuation knobs for the left and right channels, and an identical knob, labeled Bias Tests, with three positions: Operate, L ch, and R ch. Especially with a high-gain amplifier, I love having the ability to knock down that gain at the amp, as needed, and these pots let me adjust the channel balance in a day and age when few preamplifiers come with Balance knobs.

Although its Tamura output transformers are wound with three secondary taps—for 4, 8, and 16 ohms—the ATM-300R’s left- and right-channel outputs offer a choice of two loudspeaker loads, labeled Low and High; the buyer specifies ahead of time which two of the three secondaries should be made active. (Although this can be changed in the field, it’s not a job for the consumer, given how easily transformer windings can be ruined by poor soldering techniques.) On my review sample, the 4 ohm secondary was connected to the Low output, the 8 ohm secondary to High. I relied on the latter for all of my listening.

The Air Tight ATM-300R spent a lot of time in my system chained to a chore no sane man or woman would think fair: playing, four times in a row, the historic recording by Georg Solti, the Vienna Philharmonic, and a cast of soloists headed by Kirsten Flagstad and George London, of Wagner’s Das Rheingold (3 LPs, London OSA 1309). As it happens, a recent thread on Facebook had prodded me to re-read producer John Culshaw’s book Ring Resounding, about his production of that historic first complete recording of Rheingold and, ultimately, Wagner’s entire Der Ring des Nibelungen. The Air Tight amp reproduced it so gloriously well that, for lumbar herniated disc symptoms the next couple of days, one or the other of the set’s three LPs was always on my turntable.

I am old enough to have been politically ‘aware’ since the mid 1960’s. But I don’t have any strong ‘party political’ views and have never been a member, or even a supporter, of any political party. I vote for the ‘least bad’ party regardless of ‘right or left’ depending on their recent record of when they were last in power. The UK is a democracy but it is not a ‘representative’ democracy. We vote for a ‘list of promises’ called a ‘manifesto’ that each party produces, but ‘we the people’ have no say about what is on those manifestos (which are mostly lies anyway).

Theresa May is the most utterly useless PM we have ever had in all that time. She is rigid and unbending, has ‘consultations’ which are mere dummies as she listens to nobody but herself, and her new ‘Plan B’ is identical to her original, which has already been accepted by the EU who have said no less than three times that they will accept no other ‘deal’ unless it is ‘closer to the EU’, such as a full customs union. But her plan has been soundly rejected (430 to 220) by the ‘House of Commons’, which is in fact ‘sovereign’. The ‘government’ (about 20 people chosen personally by Theresa May from the 300 plus in her party who were elected, with a very rapid turnover as anyone who disagrees with her is instantly ejected and replaced) isn’t sovereign, ultimately the ‘House’ is.

I think many people are confused. The harmonic distortion is different from a typical noise in SS amp. In SS amp, noise usually means loss of information. Every time a signal passes through caps and resistors some signal is lost or altered, and there are hernia de disco lumbar ejercicios just so many caps/resistors in an SS amp. In a well-engineered tube amp, less is lost from the signal because by the design there aren’t many capacitors and resistors in the signal pass. When these manufacturers keep saying ‘shortest signal pass’, it really means fewer caps and no tiny resistors. By the way, in my personal opinion, the resistor is a bigger offender than a capacitor.

Anyway, a well engineered single-ended tube amp can keep its signal relatively purer form because there isn’t much in the signal path – but it adds something in return! Yes, a tube adds its own sound – coloration or harmonic distortion. The harmonic distortion, of course, lowers SNR, but one must understand a harmonic distortion is different from random noise. When you hear a female vocalist – you really hear her voice in a most purer form – but with an added coloration. You still get shocking sharp like 4k video – you can still see the individual pixel but with a different color saturation than the original – what was bright orange now looks dark amber. Is this accurate? Of course not. At the grand scheme dolor lumbar ejercicios of the things – it’s only 85% accurate as the original because the entire color tones have shifted. But, you can still see the individual pixel. Unlike an SS amp, where it can be 93% accurate as the original and all the color tones are same as the before – but it’s more pixelated – you can no longer see the individual pixel because more signal info was lost during the processing.

SNR for a tube amp like this can be 86db – but a listener can hear a more vivid sound compared to an SS amp with 115db. Anyway, at the end of the day, you just need to try it yourself to understand why some people buy an 8-watt amp. Personally, I have been slowly converted from a 1000 watt monoblock guy to a single-ended triode guy. I still immensely enjoy them both, and with ‘some’ genres I much prefer my SS amps.

The good thing about this ATM-300R is that more (hopefully) ATM-300s will go on the used market. Without doubt, the ATM-300 I purchased used is the best amp I’ve ever heard hands down with no exceptions, including the solid state, OTLs, and push-pull tube amps I’ve owned such as Vacs and Conrad Johnsons. The ATM-300 is the first and only amp I’ve ever heard that has ended my desire for upgrading my gear. I can and plan to live with it until I die: it’s that good. Purchased 80,000 hrs worth of NOS Sylvania and GE preamp tubes and Sylvania rectifiers : enough to keep the amp running for 46 years listening for 3 hours per day :-).

I really don’t like the mandatory feedback on this new ATM-300R version: very bad move for such an expensive amp with good output transformers. Feedback on my ATM-300 definitely ruins the sound. I would not consider the purchase of the 300R version for that reason (and also I could never afford to purchase one new, even though I would pay that money, if I had it, for the sound coming from estenosis lumbar severa my ATM-300. Its that good).

I never had a problem with 8 watts and my speakers are not very sensitive at 89db + they are 4 ohm, + they vary wildly between 12 and 4 ohms over the frequency spectrum. In my case I never use more than 1 -2 watts of power, and my tastes run the spectrum from Bach to Megadeath. If you listen at regular volume levels (70-80db) and are not listening in a large room far away from the speakers, 8 watts is fine. Calculate how much power you’ll need in your room using a SPL calculator (google: Geoff the Grey Geek Amplifier, Speaker & SPL Calculator).