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  Axiom A1400-8: 1400 Watt, 8-Channel Digital Home Theater Power Amplifier: Straight-8 Power!

      Date posted: January 30, 2008

A1400-8 Multi-channel power amplicier, Silver

Sugg. Retail: $3850 US, $3773 CA
Manufacturer:
Axiom Audio,
2885 Highway 60,
Dwight ON P0A 1H0

800-244-8796 705-635-3090
axiomaudio.com

After spending an enjoyable and interesting afternoon visiting Axiom a few months back, I came home from the Huntsville ON area with their new 8-channel digital amplifier tucked in my trunk. It’s not insubstantial at about 58 pounds boxed, and 18″ square and 4″ high unboxed. The A1400-8 has multi-plug inputs that accept balanced XLRs and 1/4″ mono or stereo phone plugs, and gold-plated plastic protected 5-way output binding posts in rows along the modular rear panel. Two sets of 8 gold-plated phono-to-RCA adaptors are provided, one L-shaped, which I recommend (if you can’t go balanced) to ensure that input cables are kept well away from output ones, because contact between these is a definite fire-breathing no-no, for reasons I’ll elaborate on presently. A 12-volt trigger connection is provided, which eliminates the need to use the front-panel power pushbutton when working with an HT preamp.

Specifications for this “fire-breathing” amplifier are a little different from those of most, starting with the ability to provide up to 1440 watts to any channel instantaneously, which can also be stated as 180-volts peak-to-peak for each per-channel output device. The more commonly stated rms figures are 350 wpc at 8 ohms, and 700 at 4 ohms, with, of course, the ability to provide 1200 wpc at 2 ohms. There aren’t any numbers specified for current.

But on the website we find the watt/channel ratios stated thusly: “Power (1 channel full and 6 channels at 1/8 power) 8 ohms - 350 watts per channel; 4 ohms - 700 wpc [my abbreviation]; 2 ohms - 800 wpc” [here I should interject that there seems to be a missing channel here, so I suspect they meant 2 channels driven] “Power (7 channels driven) All impedances - 200 watts per channel” [again, why the missing channel?]

I recorded my conversation with Axiom’s amplifier designer, Tom Cumberland, on one of my little ZOOM recorders, and referred to that SD audio card to refresh my memory on much of the technical stuff that follows. Tom does the Axiom subwoofer amp design, too, and is a very experienced electrical engineer who worked for Luxman in its audio heyday, as well as with other very respectable companies before emigrating to Canada, Dwight, Ontario and Axiom. I should note also that Tom and Ian Colquhoun, Axiom founder and speaker designer, are interviewed in a pair of short videos on the A1400-8 design brief on the Axiom web site by audio journalist Alan Lofft, a consultant to the company. Alan also has his own site, www.audiolofftreport.com, in which he provides lots of audio information, insights, and advice.
Axiom Amp designer Tom Cumberland
To make the A1400-8 work, Tom (seen left) needed a new kind of MOSFET that could swing +/-90 volts, and for this he turned to an engineer friend at International Rectifier Corporation. Each one of these custom-designed MOSFETs needed a 5-amp driver to allow it to reproduce the desired 180-volt square wave at a sampling rate of 450 kHz. This new technology is at the heart of this digital amplifier, which also required 4-layer circuit boards with 2-ounce copper coating to handle high currents at impedances as low as 2 ohms. Each channel module also has 2 dual-channel op amps for the balanced and unbalanced analog inputs. This is followed by the conversion to the very high 450 kHz sampling rate for amplification by the MOSFETS.

Tom cheerfully pointed out to me where the “juice to drive this” comes from, the giant toroidal transformer, and its large capacitors capable of 140,000 microfarads of storage to provide those 1400 watts of power instantly on demand. The inside picture clearly shows all these parts and modules neatly arranged with their orderly wire harnesses evident in this cleverly designed amplifier. Tom and his assistant Debbie Swinton gleefully showed me why you shouldn’t open this amp up and stick your finger in, by discharging the 4 large capacitors to the chassis with a screwdriver, amp unplugged. It reminded me of the time, as a boy, when I unscrewed the plug of an extension cord, having forgotten that the other end was still plugged into the wall. As I watched and heard the caps discharge, I had a reflex memory of flying across my bedroom. Of course, that was mostly current, so to speak, and this was more voltage; the latter is flashier, I surmise, but the former can really move you! And then there was the day my father-in-law was hit by lightning, but you get the idea…I daresay “fire-breathing” is not too far off the mark with the A1400-8, and its innards are not to be messed with, even when it’s unpowered.
A1400-8, inside
As a final aside about this design, it could be made to be even more potent with added transformer and capacitor power, say, utilizing a 220-volt supply to provide the “juice”, but I doubt that the practical realities of any but the biggest home theatre systems demand this. And you could always bi-amp with 2 of the current model.

Speaking of such realities, I did replace my existing monster HT amplifier with the A1400-8 for the review period. That amp is the Sunfire Cinema Grand Signature, which provides its 405 watts rms x 5 in a somewhat opposite way, with digital power supply but analog output devices. As Bob carver admitted to me a few years back when I visited him in Snohomish WA, he “voices” his amps, though the specifics of how are proprietary. But it is clear that he likes a more theatre-like bigness in his sound, with a little extra warmth, too.

The Axiom amp brought to my Newform ribbon HT speakers a more incisive and directly powerful sound that’s a little hard to characterize, and I must say that I noticed the difference more when I returned to the Cinema Grand after a couple of months with the A1400-8. We’re talking about subtle differences here, and both produce prodigious SPLs with no strain whatsoever, especially when driving the fairly benign 8-ohm load of the ribbons, which are essentially unbreakable.

Bass from the front pair of R45 s’ Scanspeak woofers was particularly tight and incisive, deep and powerful, with a hair less bloom than with the Sunfire. The Axiom amp’s midrange was very clean and seemed more directional, while the top octaves were surpassingly clean and detailed. This is a great amp that to my ears breaks new ground for digital amplification. And it does so in both clarity and dynamics, which leads to an edge-free listening experience that I’ve not heard from any previous digital amplifier. It is, I suppose, the difference between 44.1 and high resolution digital discs, and they sounded especially realistic through the A1400-8. But Dolby Digital also held up well with the better soundtracks over the review period.

If the Axiom A1400-8 is about as neutral a home theatre amp as I’ve heard sonically, it does have personality in a few other ways. I initially hooked up only 5 channels of audio to it, and immediately discovered that the fan tended to go on periodically, especially when I muted it during commercials, which, of course, made it all the more audible, rather like the fan noise from most video projectors during quiet scenes. A hand test across the top of this modular amp showed that the heated channels were those undriven, mainly 7 and 8, with a little less physical warmth felt from 6.
A1400-8, rear

A phone conversation with Tom Cumberland revealed that this amplifier prefers to be driven in all 8 channels, and the higher the input signal level, the quieter it runs, which is somewhat counter-intuitive, but “there it is” (as the Archduke frequently noted in the film Amadeus). Now, it doesn’t matter if there are no speakers connected (as it does with tube amps), just that the input be loaded with a voltage to, rather paradoxically, cool off its op amps. That, I suppose, is just one of the things I’ll never understand about digital amps.

Using the balanced inputs for the main 5, I also had unused unbalanced outs available from the Sunfire Theatre Grand II preamp, which I hooked up to the warmer-than-necessary channels, and this seemed to solve the problem, though I still had to turn the Axiom off manually when not using the system. Of course, if I’d also had a 12-volt trigger cable, I could have solved this problem, too.

So, aside from occasional relay clicking when the sound was muted, there were no further anomalies or unwanted utterances from the A1400-8, just clean, extremely powerful sound all around. I was repeatedly struck not only by the sheer dynamics, but the micro-dynamics that revealed all kinds of things going on around me, especially in shows I watch regularly that have a lot of this, the original CSI being one, and Navy CIS (my favourite; I guess these days I identify with crotchety old codgers like Jethro Gibbs) being another. This was also true of many sports broadcasts, basketball in particular, but also Hockey Night in Canada, with its great rink-side sound. In all sports you could hear all of this stuff going on, people walking across, or down the sides, and on golf, cheers going up from other holes, though the rapid cuts made this less riveting.

I’m not saying I don’t hear this with the Signature amp, just that there’s a little more bubble-up effect from the exceptional micro-dynamics of the Axiom. Perhaps that could be attributed to the A1400-8 ’s ability to distribute its power so quickly and effortlessly. And here I suppose I’m micro-comparing two exceptionally powerful amplifiers that stand well above the crowd of wimpy 100-wpc receivers out there. The next stage up from here is 8 monoblocks, I suppose, but interestingly enough, Ian Colquhoun commented to me in passing that he preferred the new amp to his previous custom multi-monoblock setup. There may be areas of synergy here that are beyond our current exploration. And, yes, current out of the wall might just have something to do with it, since digital amplifiers need less of that.

Doing it this way surely provides the synergy that keeps costs reasonable, along with having enough out-of-the-wall current (think 220-volt again for more) going to the highly efficient digital amplification. Here we have an amp that may seem expensive until you divide the price by the channel complement, which yields a per-channel retail cost of just over $400.00. And though you do have to buy them all, you can use 7 and 8 to drive remote speakers, or dream up your own applications, which, with the output capabilities of most HT preamps, will most likely add up to at least 7 channels, anyway.

Maybe that’s a good point at which to conclude. I thoroughly enjoyed my time with the Axiom A1400-8, and will seriously consider it when I upgrade from my Sunfire system, which, unfortunately, is not likely in the immediate future, as other priorities prevail. But, some day…

Andrew Marshall

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2 Responses to “Axiom A1400-8: 1400 Watt, 8-Channel Digital Home Theater Power Amplifier: Straight-8 Power!”

  1. Angelo Cognito c-ca Says:

    Good afternoon, mister Marshall,

    I read with interest this review. What do you think about the stereo version of this amp (the Axiom A1400-2)?

    I still have the project to buy a Bryston 4bsst2 but this amp has great advantages (linked with WAF, smaller, less heat and with the possibility to hide it in a drawer of the or behind a door of the audio stand and it also canadian, a big factor these days). Does it stand the comparaison?

    Thanks and regards

    Syl

  2. Andrew Marshall c-unknown Says:

    Hi Syl (or Angelo),

    You may not be aware that Bryston has also introduced some digital multichannel amplifiers, and these may be comparable to the Axiom in both quality and price. I’ve heard some pretty good little digital amps, including the ones recently reviewed (Trends Audio TA-10, etc.), which replace the finesse and pure power of the SSTs with a very lively, engaging presentation.

    When it comes to amps, not much is better than the great Brystons regardless of cost, but there are many that come close at much lower cost. Only your ears can decide.

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