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Abbingdon Music Research AM-77 Amplifier Review

Special Report: Chris Redmond on Abbingdon Music Research Part I: AM-77 dual-mono amplifier

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Abbingdon Music Research AM-77 Amplifier

Introduction

If you are given the opportunity to audition an SET amp in your own system, as ridiculous as it may sound, I’d speculate that for many it will be a decision similar to Alice’s when offered a choice of two pills in Lewis Carol’s classic tale Alice in Wonderland, or if you’re more the Play-station generation, think of Neo from the almost equally classic sci-fi spectacular, The Matrix.

Taking the blue pill meant waking up safely in bed to carry on your life as normal, but taking the red pill meant….well, basically you are transported to Wonderland and your perception of the World is changed forever.

For me, even though I’d heard SET amplification previously in numerous systems and been impressed, it was only when reviewing the Audio Note Quest Silvers over an extended period of time in my own system that I realised there was no going back to conventional amplification, primarily but not exclusively when considering that all important midrange – not even the resident E.A.R 509 valve amps or the pure-Class A Sugden A21Se, which both put most typical solid-state amps to shame in the midrange with their delightful liquidity – could tempt me back up the rabbit-hole, and I knew I’d be mad as a Hatter not to make the change to SETs at the earliest opportunity (which equated to when funds allowed.)

There is a proviso here however, as the 8Wpc Quest Silvers were only able to fully demonstrate their magical qualities due to the high-efficiency of the resident Audio Note AN-E Spe/HE speakers which tend to be the preserve of your more enlightened enthusiast (!!) who has already forsaken more mainstream solid-state amplification in favour of SET or lower-powered Class A transistor amps.

I’m pretty sure that the vast majority of readers glued to this review will be using speakers around the 85 – 88dB sensitivity range, which probably encompasses 90% of the most opular high-end modern transducers.

The Revel Performa F30s in the living room on HT duties are 87dB for instance, and the recently acquired Dynaudio Contour 1.3 Mk2s are 86dB, so for the purpose of this review we’ll assume these are a typical load and the Audio Note AN-Es with their additional 10dB sensitivity can have a back seat. What does muddy the water just a little in my own head when making comparisons is that the SET amp I now use is the Border Patrol WE300B, complete with an off-board power supply which lifts bass performance way above that of your average 8Wpc SET amp.

For now it’s back to the pills.

If you haven’t broken your cherry yet when it comes to valves, you’ll still be aware that many audiophiles swear by valves for the warmth they add (or don’t lose) in the midrange, and even if they don’t use valve power amps they’ll probably extol the virtuous marriage of a valve preamp to a solid-state power amp which can be an excellent introduction to the effect of having a ‘bit of bottle’ in circuit.

Valve output CD players are also quite popular nowadays (although many aren’t true valve output) and these too are a ‘toe in the water’ for many who perhaps wish to tame a little of that forwardness or hardness endemic in many all solid-state audio systems, but both of these are safe options for the solid-state diehards because, of course, the main drawback of valves in the eyes of the masses is avoided, this being power – or rather, the lack of power.

Yes, we do have some valves amps from the likes of E.A.R, Audio Research, and B.A.T to name a few which have wattages into three figures, my E.A.R 509s being 100Wpc, but they don’t come cheap and usually have a multitude of valves in order to attain their solid-state comparable power output; the 100Wpc Audio research D-115 Mk2 has a compliment of 17 valves for instance – fancy coughing up for a re-valve anyone?

Generally speaking, although straddling the two I’ve found that such amps – invariably push pull – have a presentation which is actually as close to solid-state as it is to SET, yet they can be superb amps in their own right and can directly replace a solid-state amplifier in a system using speakers similar to the aforementioned Revels and Dynaudios. There’s every chance you’ll have a very nice sounding system with this scenario……however, we’re still in blue pill territory and while some of the delights of valves will be suggestively stroking your earlobes, the foreplay doesn’t go any further as that seductive SET midrange is frustratingly absent whenever you load a CD and press PLAY.

Does it sound like there could be a gap in the market for an amp which has none of the power restrictions of SETs but gets closer to the midrange magic than push-pull?

AMR AM-77

Thorsten Loesch is the Technical Director of Abbingdon Music Research, and having already taken the red pill himself many years ago it possibly crossed his mind that there was indeed a market for such an amp.

The AMR AM-77 is something of a refinement of the popular valve preamp, transistor power amp combination only in a single chassis with two 5687/6900 (NOS) valves operating in pure class A in the first preamplification stage, allied to bipolar output devices in the power amp section which utilize a 1200 VA custom double C-core transformer. Power output is rated at 270 watts per channel into 8 ohms, and in line with your typical valve amp this wattage also holds true for a 4-ohm load. It should be noted that the figure of 270 watts is the IHF dynamic rating which is a standard international rating relating to the power an amp can put out for a short burst of 20ms.

Now, although this makes for a very impressive marketing blurb, AMR actually prefer the more relevant rating system of the Federal Trade Commission (FTC), as this measures the average output over a stated frequency range with both channels driven continuously, even though as a non-US-based Company AMR aren’t required to give the FTC rating of their products.

They include the FTC rating in their literature for the benefit of their customers, so kudos to AMR and it does make meaningful comparisons to other FTC-rated equipment simple. The fact that the FTC rating for the AM-77 is still a hefty 180 watts per channel does mean that nobody should have any worries about a lack of ’oomph’, but in the unlikely event there is a somebody out there with a power fetish there is the option of buying a second AM-77 and operating both in monoblock mode, which would give 320 watts into a 4- or 2-ohm load; such a fetishist would presumably then never leave the house and would live off pizzas posted through their letter box. (British English is truly elegant; the U.S.-equivalent of the last few words in the last sentence would read as “pizzas delivered to your mailbox.” –Ed.)

I’ve already mentioned the monoblock option so as you’d expect the AM-77 can also operate as a stereo power amp as well as in the default PRE-MAIN AMPLIFIER MODE, otherwise known as ’integrated’ to you and me, all selectable via a switch on the rear, so no need to remove the casing and mess around with jumpers or whatever.

The versatility of the AM-77 is in fact a major plus, opening it’s use up to the ever-growing home theatre market on account of a HOME THEATRE DIRECT option, allowing an external processor to control volume, and no this isn’t just a case of selecting the power amp option, as one of the “amps inputs” can have it’s level fixed to account for the typical HT outputs of 0.775V (0dBu) or 1.55V (+6dBu).

Integrating HT into a high-end two-channel system is a problem many of us with no separate listening room have devoted a considerable amount of chin scratching to, and I decided some time ago that the compromises were too great so one had to retire to the bedroom. If I’d owned an AMR AM-77, there’s every chance they’d have co-existed quite happily with the logical upgrade path of installing more AMR AM-77s when funds allowed an additional consideration.

Plenty of ways to configure the AMR AM-77, then, with almost endless permutations if you add more, but I’ll restrict my impressions to its operation as an integrated, otherwise by the time I’ve finished my review the model I’m using could have been replaced by some “Mk2/3/4 Signature Special Edition” version, such is the dedication to improving AMR’s line up even further.

In fact, anyone attending the 2008 CES may have come across a new debutant.

From AMR’s website, “the AM-77 (Control Centre Edition) – an AM-77 with an Active Crossover to handle the high frequency signal and send the low frequency signal to a second standard AM-77 (or 2nd and 3rd standard AM-77 in Monoblock mode). The Control Center forms the heart of AMR’s active system, which takes the listener one notch closer to the original source.”

Even James Bond would have his work cut out preventing AMR’s bid for World domination.

Out The Box

Following this review will be a write up of the AMR CD-77 which I’ve had for a couple of months now, and both the AM-77 and CD-77 share the same chassis designed around the classic “golden ratio” dimensions, which keeps manufacturing costs down and ensures a perfect aesthetic match. Because the CD player incorporates substantial power supplies and benefits from having plenty of room for air flow around the valves, the chassis had to be made larger than your average CD player’s, ensuring that no compromises needed to be made in the amplifier’s topology to squeeze everything in.

Indeed, AMR uses no heat sinks in the AM-77 to disperse heat and compare them to tuning forks due to their potential to impart resonances to the audio circuit. Both CD-77 and AM-77 use symmetrical dual mono layouts so the cooling vents either side of each window above – which also allow the internal blue LEDs to illuminate proceedings – are positioned correctly above the valves for amp and CDP.

Despite the heading ’out of the box’, the AM-77 is actually shipped in a virtually bomb-proof, foam lined aluminium flight case (…which comes in a box) containing the following.

i. AM-77Reference Class Dual-Mono Pre-Main Amplifier.
ii. RC-77 Remote Commander (with 2 x AAA batteries).
iii. PC-77 OptiLink® Reference mains power cable.
iv. IC-77 OptiLink® Reference interconnect cable (XLR-type).
v. Synchronisation (3.5mm jack) cable (for linking-up multiple AM-77s).
vi. AM-77 Owner’s Manual.
vii. Quick-Start Card.
viii. AMR Warranty Card.
ix. AMR Test Disk.

The RC-77 in particular deserves mention. Better engineered than many components (in the finish you’ve selected for your amp), it is motion sensitive so the touch screen illuminates when you pick it up displaying controls for the amp and CDP, whereas circular push buttons for functions which are used most frequently are positioned below the screen .

As with the CD-77, there are just five controls on the amps facia which comprise;

F1. STANDBY switch: to place the AM-77 in active or standby mode.
F2. SOURCE selection buttons: to select between the 5 different inputs (two of)
F3. VOLUME buttons: to adjust the volume level (two of).

A further two are situated on the right hand edge of the facia out of sight to keep things neat;

F4. iPod 3.5 Input Connector: for the connection of an iPod or similar portable music device.
F5. iPod USB charging connector: for re-charging an iPod or similar portable music device.

On the rear of the AM-77 we have:

* R1. SPADE/BANANA outputs: for connection of standard termination speaker cables.
* R2. SPEAKON outputs: for connection of Speakon terminated speaker cables.
* R3. HIFI/PRO switch: to allow for a source with transformer balanced output*.
* R4. INT/POWER Amp switch: to alternate between Pre-Main and Power Amplification settings*.
* R5. MODE switch: to alternate between Stereo/Monoblock/Bi-Amplification settings*.
* R6. INPUT 1: shared XLR and RCA input, for signal input of source equipment.
* R7. INPUTS 2-5: RCA inputs, for signal input of source equipment.
* R8. SYNC connectors: for connection of more than one AM-77*.
* R9. RS232 option connector: to facilitate future upgrades*.
* R10. Infra-Red Link: for connection of a wireline remote control.
* R11. IEC power connector: for the connection of a PC-77 mains power cable to the AM-77.
* R12. POWER Switch: to switch on mains electricity to the AM-77.

Amp and ancillaries out the box then, up it goes onto the newly installed Target Audio isolation shelf where it is duly spoiled rotten by being plugged into the PS Audio P600 power regenerator providing the purest 230 volts available. I might even have heard the AM-77 give a sigh of appreciation such as a lady would give when biting into the finest Belgian chocolate…

Powered Up And Ready To Go

After waiting for the facia displayed 45-second count down to “optimise supply voltage”’, the reference Marantz CD-7 began feeding it a diet of not Belgian chocolate but the Telarc‘s Got More Blues – New Blues For 2000 13-track sampler (CD-83503).

Immediately apparent was that this wasn’t a million miles away from the Border Patrol SET amp/Audio Note AN/E combination I was already acclimatised to – let’s say something akin to going from two sugars in your coffee to one and a bit – although here I was using the Dynaudio Contour 1.3 Mk2s which are accepted to be even more ‘power hungry’ than their 86dB rating suggests.

I say not a million miles away, but this should be qualified by stating that in my opinion and experience, nothing can match the nimble dexterity, the dynamic capabilities and the overall ‘live’ quality of SETs allied to a compatible speaker. Bearing this in mind however, music played through the AMR-77 undeniably had some of that SET pixie-dust sprinkled over it, and I’d go so far as to suggest that AMR have succeeded in placing their amp somewhere between push-pull valve amplification and SET in terms of midrange naturalness, ambience and insight and all with just two valves in circuit,.

Resolution was top notch as you’d expect after reading the amp’s specification, noting the component quality and the attention to detail of a company which really has made a definite statement of intent with the first designs put into production.

For the next hour, the Telarc disc demonstrated the amp’s ability to reproduce and differentiate between the varying tonal qualities of guitars played by the likes of Terry Evans, Ronnie Earl, Robert Lockwood Jr and that old stalwart, Mighty Sam McClain, without me suffering any Border Patrol withdrawal symptoms at all. Yes, I preferred the BP – the red pill was more potent than a boat load of Viagra – but this was very nice indeed thank you very much, and being a power amp the Border Patrol was by necessity partnered with the Audio Note M3; add on the cost of the Kimber Select KS-1030 interconnects and this brought the cost up to around double the price of the AM-77.

Hmmm…….two AM-77s perhaps?

Bass lines where reproduced with excellent tonality once again, and although lacking the ultimate punch of comparatively powered transistor output amplification and the better push-pull designs such as my own EAR 509s, this was more than made up for by the integration of the bass and it’s quality rather than quantity – not unlike SET amplification with high-sensitivity speakers, in fact.

Over the course of the next few weeks, that first impression of effortless musicality was reinforced, and significantly I found myself listening to as much music as I had previously with my own amp which is something I hadn’t anticipated before the AM-77 arrived, if I’m honest.

Initially when requesting the amp be submitted for review, it was after delivery of the company’s first product and hence more publicised CD-77 which, from a selfish point of view, I was extremely interested in as a potential upgrade for my own system, whereas the amp was something I was interested in purely as a review piece because it matched the CD-77 and was designed by the same guy who apparently shared my idea of what constituted good sound if the CD-77 was anything to go by.

Now however, I’d hazard a guess and suggest that had I heard the AM-77 before hearing the Audio Note Quest Silvers and later purchasing the Border Patrol, I may well have ended up buying the AMR even though as previously mentioned I’d heard SETs in systems other than my own quite a few times.

Out of interest I did connect the class A solid-state integrated Sugden A21SE up which had so impressed me when driving the AN/Es, but immediately the sound coarsened up ever so slightly although still sweet by typical SS standards and the 30Wpc Sugden definitely wasn’t comfortable with the Contour Mk2s even though it had given quite a good account of itself when driving the Revel F30s at a similar 87dB sensitivity; see what I mean about the Dynaudios?

Reinstalling the AM-77 added the missing body, ambience and control the Sugden was almost able to replicate with the AN/Es, although not quite; still some feat for a £2,500 (in the UK) amp however.

In conclusion then, I take my hat off to Mr Thorsten Loesch and those who had the foresight and finances to back him when setting up AMR in a marketplace where consumers are now constantly urged by the big multi-nationals to invest in home theatre, ‘newer’ technologies and formats.

Delivering a blow for good ol’ stereo and substance over hype, the AM-77 is one of the most versatile pieces of audio equipment I’ve come across and as such is a very safe, future proof investment which on it’s own is capable of providing an owner with a taste of the high-end and a sip of single-ended triode magic, all at an affordable and positively bargain price when considering the quality of both the construction and performance on offer.

The options to reconfigure an existing AM-77, add one or even more AM-77s means anyone happy with the tonal character of his AM-77 has a predetermined upgrade path, something I personally believe to be crucial if some of the pitfalls of system development are to be avoided. AMR have certainly done their homework well and have landed on the manufacturing airport strip running, with a package to satisfy even the most discerning audiophile.

Thoroughly recommended then, but bearing in mind my own preference for a full system approach to audio, wouldn’t it be interesting to hear the AM-77 with the company’s own CD-77?

Tune in next issue for the second AMR review then and you’ll find out, and furthermore I’ve just received a pair of speakers affectionately and aptly nick-named ‘Baby Rhinos’, otherwise known as the AMR LS-77s; that’ll be AMR review number three then – no rest for the wicked eh?

Manufacturer’s Comment:

Dear Dagogo,

We are very proud and honoured to be contributing to this multi-component review which is the first time we have had our equipment reviewed this way.

Your reviewer Chris Redmond, is one of only a handful of reviewers that in our humble opinion, truly understands what AMR is trying to achieve through its components. That is, to bring the musical enjoyment that Single Ended Triodes uniquely offer to the major market of medium-efficiency speakers.

At AMR, we hold the AM-77 in an even higher regard for what it has accomplished as a real-world amplifier than the CD-77 which we are already ecstatic about.

All we can say is a very hearty “thank you” for a most insightful review of the AM-77.

Many thanks
Directors and Staff of Abbingdon Music Reserach

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