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Why an expensive integrated? Why not separates?
By definition and virtue of their voltage gain stages mated to power buffers, commercial consumer amplifiers -- FirstWatt's F4 being the sole exception I'm aware of -- are really single-input integrateds. Wedding them to traditional active preamplifiers where active equals gain places multiple voltage gain blocks in series. This often produces excess playback levels and gain must be thrown away with deep attenuation. In short, audiophiles who combine active preamps with conventional power amps run preamps ahead of integrateds. If you believe that simpler is merrier and a shorter signal path better, AM-77's simple two-stage circuit should have more appeal. It could answer the question of why an expensive integrated like it could be preferable to separates on principle.

That's a rarely talked-about concept in a market where the inherent superiority of separates has been touted as the go-to destination for superior performance. As a result, most serious audiophiles own separates already. To propose that they replace those with an integrated is any marketeer's nightmare. It's far easier to drum up excitement for an esoteric source with the "source is paramount" slogan.

If you're already invested in state-of-the-art preamps as I am with the Supratek Cabernet Dual and ModWright LS-36.5, running the AM-77 as an amplifier through input 1 on XLR or RCA (fixed to direct mode by rear selector) throws away half of what you paid for. You'd think. Actually, not. An external preamps taps into the AM-77 ahead of the 5687 voltage gain stage. All you really throw away is the AMR's input volume control. That trims the input signal before it enters the amp's circuit gain of 36dB. It's thus sane and feasible to combine the AM-77 with your favorite standalone preamp.

You might regard the rear panel SpeakOns with suspicion. While plainly superior to hifi's ubiquitous binding posts, they're a no-show in consumer audio and thus a curiosity in home audio. If you mean to subwoof with hifi rather than pro-terminated cables, you'll have to either stack spades or run a spade/banana combo. If you biwire a main speaker with discrete runs and run a subwoofer, the lack of a second pair of conventional 5-way binding posts nearly enforces the use of SpeakOns. Twin pairs of conventional speaker terminals would seem rather more practical. Still, knowing Loesch's pro roots, he must consider even the single pair of 5-way posts a compromise. As a consumer by proxy however, I would have voted for twin pairs of conventional terminals. Plus variable outputs. Then I learned that AMR regards the SpeaksOns as expansion ports of sort. Vince Luke dispatched a temporary SpeakOn-to-RCA cable pair which would facilitate non-AMR biamp scenarios such as my big Zu speakers demand. AMR plans to invest in various adapters that can convert the SpeakOn ports to RCA plugs, 5-way binding posts or other interfaces.

This segues neatly into the raison d'être for all purist fi: tweaked performance. To evaluate the implementation of 2-stage tube voltage-gain block + transistor power buffer/impedance converter, I began my test with the single-wired 89dB Polish Eryk S Concept Ketsu Superb towers. That's because those could also be run off the ModWright LS-36.5 tube line stage and FirstWatt F4 for a $,7,500 combo of similar simplicity, albeit spread out over two components.

Source + integrated, add speakers - that's the AMR concept of the 77 components and AMR speakers are forthcoming next

But first, a quickie comment vis-à-vis the 450-watt Coda CX monos that had vacated the AMR's spot on this speaker pair. The AM-77 clearly had a tonally more developed richer treble and thus was painting upper harmonics with greater sweetness and texture.

It seemed a bit as though I was back listening to my favorite valve amp, the Yamamoto A-08S 45 SET. Needless to say, it couldn't drive this speaker. The noteworthy connection was simply how the AMR amp, dimensionally and in the treble, behaved not unlike a zero feedback direct-heated valve amp. Even without Thorsten Loesch claiming SET sonics with transistor muscle for their beast, this was my first spontaneous inkling of just such a design brief.

The moment low output impedance, current drive and massive power enter, we've of course already left the SET reservation. How this needn't be a bad thing was chronicled in my review of the First Watt F4. Preceded by the mighty Supratek Cabernet Dual DHT preamp, I'd arrived at a virtual best of both worlds scenario. It had made 'pure' traditional SET drive sloppy and fuzzy by comparison. Here's a summary quote:

"The most obvious difference of inserting direct-heated triodes into the signal path [this was running the F4 as a follower, taking its input from the output of a SET - Ed.] was the rounding-over action on transients which, depending on tastes, made the high-current F4-squared setup [running two F4s in mono - Ed.] just slightly brutal on energetic fare into these high-eff speakers. 2nd-order distortion creates a modicum of subtle fuzz 'n' fluff between notes especially when things get thick and complex. The transistors sounded cleaner by comparison, the tubes more comfy. The big question was, what would change when the F4s were extracted from the chain? Good grief, everything softened further and hazed over. From the midrange on down, grip loosened so considerably as to, from tube man no less, become unacceptably ill-defined by comparison. This sad truth transmitted uncut because the modified Eminence widebanders driven by the tubes are solidly good to 40Hz... this was a most instructive outcome, quite shocking in how unambiguously superior the buffer amp concept was to valves pure. It demonstrated in no uncertain terms what optimized invariant loading of a direct-heated triode (now merely seeing a resistor) plus transistor-sourced current into a far lower output impedance sounds like."

In short, the unusual concept of combining the virtues of superior direct-heated power triodes with low output impedance and substantial current gain had won the race rather decisively. Neither the AM-77 nor the ModWright LS-36.5 use direct-heated power triodes of course. They employ small-signal 5687s and 6H30s respectively. How those would compare to real 45s strapped to a transistor power buffer in the above scenario was to be the next experiment. To have sufficient voltage gain for this suite of tests without altering further variables, the Polish Ancient Audio Lektor Prime CDP with 6H30-powered output stage and variable gain up to a colossal 7V became source of choice. Laissez les bon temps roulez.

The ModWright/FirstWatt combo clearly had higher resolving power. It suggested a further drop in the noise floor (the low-gain LS-36.5 uses output transformer coupling for 125dB of S/N and the F4's noise floor is 60uV unweighted). This opened up the rear and back corners of the stage by providing increased ambient recovery. It simultaneously put me closer to the lead singer or instrumentalist by hearing more tertiary stuff like lip smacks, head movements or a sax player's bodily gyrations during Motown funk solos. Further grippiness or edge definition also inserted itself across the audible range, with more rebound tension especially on the bass. Did I hear the effects of higher current gain? After all, it's the only thing the F4 concerns itself with. Let's just say it sure sounded like it. Bass articulation and weight were the most obvious beneficiaries but the enhanced tautness/articulation was universal and the increase in resolution over the AM-77 was incontestable.

Aspects like tonal warmth, image density and musical flow between both presentations were quite similar, however. Splitting the AM-77's functionality into those particular two discrete components simply acted like a blood thinner. It made everything seem a touch faster, lighter,

harder hitting and dimensionally more lit up and hence, vaster. For my tastes, the 36.5/F4 combo held the aces. In the same breath, this speaker's sensitivity rating and this preamp's max 12dB gain coupled to the zero-gain amp presented about the SPL limit for how this system can fill my space with the necessary volumes. Low recorded median levels could already require the occasional increase of source output voltage up to double the industry standard. The AM-77's reach certainly extends significantly farther. As we shall see, it includes challenging loads like Mark & Daniel's 82.5dB 4-ohm Ruby.

Inserting my 2-watt Yamamoto ahead of the F4 increases system gain significantly to nearly -- but not entirely -- keep up with the AM-77 regarding what I can drive with it. Subbing in the 26dB Supratek Cabernet Dual levels out things completely. More relevant in this context was the simple admission that power triodes, without obscuring, do things for nearly psychedelic holography, spatial sculpting and tone color temperatures that small signal triodes cannot. Of course, this lineup rather complicated the box count. It also exceeded the AM-77's budget by a good 2K. Rather than raining on Abbingdon Music's parade, this quick excursion into left-field esoterica merely demonstrated the outer possible limits in this general context and what one should realistically expect of the AM-77. It does not really sound like a DHT zero-feedback amp with muscle. The only ones to really appreciate that will be those who can actually follow a superior SET with an external transistor power buffer.
Does the AM-77 sound like a good tube preamp then when mated to a good transistor amp - which it seems to be, in one box? Not really.

Its transients are softer than solid-state, very much like the usual power tubes in fact. The AM-77 also sounded a bit underdamped on my usual speakers, translating as a lack of bass grip. In each case, switching in my AudioSector Patek SE, FirstWatt F4/s or the Red Wine Audio Signature 30.2 on review -- all incidentally far less powerful to remove that argument from the discussion -- produced more transient pop, more across-the-board grippiness, firmer bass and less fluff around the notes.

While on reality checks, the $2,500 Signature 30.2 replaced the F4 so it too was being driven from the ModWright preamp. Déjà vu all over. Reducing box count, this sounded very much like the Yamamoto/F4 follower combo, albeit even fleshier and warmer if not quite as preternaturally resolved. Costing $3,000 less to again equal the AM-77, this was a financial apples-to-apples comparison (but without expensive EML bottles giving up the ghost just outside their 1-year warranty). Feature wise, it was a near wash. The LS-36.5 added a second RCA main out plus tape loop and the 30.2 its own preamp output; the AMR its USB input. Sonically, the AM-77 was paler, less voluptuous, less dense, lighter in the bass and not quite as compelling. Busy with a new painting in the adjacent living room, my wife quipped "how come that Red Wine box makes everything sound so much better?" That innocent question is really loaded. The answer should trouble many amplifier designers.

The verdict thus far? The AM-77, on speakers like the above and anything with higher voltage sensitivity like my Zus, WLMs and Rethms, was outclassed by the LS-36.5/30.2 and LS-36.5/F4 combos, both priced to compete head on. The AM-77 sounded warm, comfortable, robust and very dynamic but not as accurate, precise and resolved, Frankly, it sounded somewhat underdamped.
Time to draft the heavy artillery - the small but challenging Mark & Daniel Rubies.

With my black granite Lektor Prime set to 2V out, the 30dB Red Wine unattenuated, the LS-36.5's pot sat at 2:00 o'clock for customary volumes. Though perhaps stretching credulity given the 30.2's 30-watt rating -- its ultra high-current battery supply more than makes up for it -- the resultant sound was super robust, meaty, dynamic, colorful and completely uncompromised. The only thing slightly better on the Ruby had been Coda's just departed 450-watt CX monos.

The AM-77 was mellower, again not quite as grippy, not quite as ballsy down low. Yet strangely, the differences compared to the Ketsu Supremes and my usual hi-eff speakers had far more equalized now. It suggested, perhaps, that the AM-77 likes to be 'loaded down' a bit to enter its optimal power band. Seeing that AMR's forthcoming speakers mimic the Rubies in being small forced alignments that soak up power but are capable of essentially full-range performance, this assumption has some back up. With Mark & Daniel's mini speaker, the presentational differences were now down to listener preference rather than any incontestable better and worse rankings - and the AM-77's volume control was well in its last quarter. Taking my cues, the Rubies soon vacated the building in favor of their Maximus elders whose F3 of 36Hz isn't a misprint and whose curved air motion transformer down to 800Hz upstages the Ruby's smaller flat units.

I was confident that with the Maximii, the AM-77 was finally fully in its element. It behaved like a powerful push/pull tube amp - warm, robust, dynamic, with slightly rounded-over edges, big dense staging but not as finessed and insightful as FirstWatt's F4 or the high-current RWA T-amp. It won't be lost on the counting reader that the AM-77 reaches a lot deeper into the wallet, explaining my lack of overt enthusiasm. Had I big speakers in the house where my amps' ambitions exceeded their reach and the AM-77 filled the gap, I'd more appreciate it. But with the Red Wine amp man-handling even the 82.5dB Rubies with a burlier fist, I felt a bit out of the loop. This e-mail from staffers Marja & Henk didn't help: "Speaking of Franck Tchang, when in Denver at the RMAF show this year, our pilot friend Darren was playing the AMR amp on Franck's Tango speakers. It was clear that the combination was not really successful. The AMR amp seems to lack sufficient damping factor. Compared to the Tango we heard in combination with the big Karan amps, in Denver the bass lacked tightness and control. Now that you have the AMR on hand, did you notice any of this?" Cough.

If AMR's project brief was to combine the best of tube and transistors, most would argue that the latter has to, first and foremost, include superior bass control. The way I hear it, what AMR has really done is create a powerful push/pull tube amp without maintenance-intensive output bottles. To get 180wpc from valves usually means quite the tube forest. To get related sonics without the heat, noise, drift, aging and potential failures is quite the crafty proposition. To get fully behind that, I just had to abandon whatever X-class assumptions I'd somehow held about the AM-77.
Once I viewed it as a high-power tube amp without tubes, it all added up. To drive Mark & Daniel's Maximus Monitor with tubes... that's an exciting stunt.

Slipping into the spot vacated by Coda's 450-watt CX monos, I heard on these monitors exactly what one would predict by now: tonal warmth, image density and heft galore; big broad dynamics; wide lateral staging, less extreme depth and rear-of-stage illumination; less instrumental and vocal auras against space, somewhat rotund puffy bass for more bloom than hard slam; and overall sweetness rather than the last word on treble elucidation and the secret life of cymbals.

Huge and hugely heavy, the AM-77 is nevertheless ultra quiet in operation and only warmed to the touch on the loads I could throw at it. With a very snazzy touch-screen enabled, motion-sensitive back-lit remote that allows complete dim of display and controls illumination, the user interface writes chapter and verse on how to do such things. Feature-wise and until the SpeakOn converters become available, the AM-77 lacks pre-outs to subwoof or biamp with non-AMR amplifiers. Universal voltage compatibility and AC line self diagnostics are a big plus as are the champagne and Titanium color options. The power rating can be deceiving if used to extrapolate in particular bass performance. There the AM-77 is decidedly softer than quarter-powered superior transistor amps. In that department -- but full-range really for transient definition -- this integrated acts like a tube amp with highish output impedance and low damping factor. As a direct result, inner resolution is somewhat hooded compared to the very best and the micro scale of dynamic fluctuations suppressed. Strong points are zero listener fatigue, sonic voluptuousness and properly scaling macrodynamics. The ideal target audience seems to be folks who've lusted after 200wpc valve amps but couldn't deal with the glowing glass. While there are tubes in the AM-77, they're of the long-lived small-signal type. This should have no significant impact on maintenance costs or intervals. Though conceptually a hybrid to suggest an Oreo cookie mix of qualities, the AM-77, first and foremost, sounds like a good, powerful push/pull valve beast. If that describes you, Abbingdon Music Research's AM-77 integrated could be a perfect match with your needs and desires.
Quality of packing: Fully padded aluminum flight case.
Reusability of packing: Indefinitely..
Ease of unpacking/repacking: Easy but the unit is very heavy and big.
Condition of component received: Perfect.
Completeness of delivery: Power cord, owner's manual, AMR CD, SpeakOn-to-RCA leads submitted later.
Quality of owner's manual: First class and, like the remote, a poster child for how to do it.
Ease of assembly: None required. Tube replacement requires removal of top cover.
Website comments: Plenty of photographs and technical White Papers to be very complete.
Warranty: 1 year factory warranty for the modified machine.
Human interactions: Prompt and professional.
Pricing: For the build quality and general concept, very aggressive.
Final comments & suggestions: Increase bass damping; add pre-out; add second pair of conventional 5-way binding posts.

Abbingdon Music Research replies:
Dear Srajan,
Many thanks for your efforts and sonic interpretation of the AM-77.

Your comment that the AM-77 sounds like a lush push-pull valve amplifier done well pleases us greatly. We think you "hit the nail on the head" with your final comment that we have succeeded in bringing out the best attributes of "valve" performance from a hybrid amplifier". This was our original design objective as the AM-77 is aimed squarely at mid to low-efficiency speakers (<90dB) which comprises the lion's share of the speaker market.

Coming from a background of vinyl, single-ended triode (SET) valve amplifiers and high-efficiency speakers, we also agree that when partnered with a pair of high-efficiency speakers rated at 97dB at 180-watts, the AM-77 is not a match for a pure-bred SET amplifier.

The reason we found was that a number of complex relationships combine so that if an amplifier possesses a certain degree of mainly 2nd order harmonic distortion, it will actually compensate some of the fairly high distortion present in most speakers. With less detail hidden under the speaker's own harmonic distortion, the result is a cleaner, more detailed reproduction of music.

Whereas a 300B or 45 SET amplifier may have enough 2nd harmonic distortion for this effect to become beneficial with high-efficiency speakers; the AM-77 with its lower distortion level does not produce this synergy with the same high-efficiency speaker.

This again goes back to our remit that the AM-77 was designed to compliment "mainstream audiophile speakers", which require a different relationship between the power and low-order harmonic distortion levels that suit mid to low-efficiency speakers.

We can also confirm that there will be a dealer/distributor fittable preamplifier output (plus a number of other options we currently are implementing) that will use the Sub-D9 option connector along with a suitable breakout wiring harness.

Many thanks again for your great work from the staff and directors at AMR.
Manufacturer's website