Axiom Audio A1400-8 Listening Tests

All of my direct listening comparisons between the A1400-8 and my much more expensive Denon POA-A1HDCI amplifier (MSRP: $7500) was with the latter being configured into bridged mode. This put the Denon amplifier on near equal power footing with the A1400-8. The preamp gain was adjusted -4dB when listening to the Axiom amp for proper level matching. On average it took me about 20 seconds to swap the cables and level match when doing direct comparisons between the two amplifiers making it a very difficult task to point out the subjective differences I was hearing since both amplifiers exhibited exemplary fidelity. Listening comparisons between the Denon and Axiom amps were not done for multi-channel due to the complexity of changing cables and level matching and the fact that it’s easier to discern sonic differences in stereo as opposed to multi-channel. This is especially true since both amplifiers have huge power supplies and are fully capable of hitting reference levels in my theater room without sacrificing performance whether powering two or all seven speakers.

Critical listening tests were conducted mostly with two-channel sources such as CD’s and SACD’s. Multi-channel listening tests were conducted for extended periods of time at reference levels to ensure the amplifier was capable of unfaltering sustained output in my theater room.

CD: Fourplay – The Best Of Fourplay

I always like a little Fourplay before really getting into the thick of things. Track #5 “The Chant” is a song I often use to separate the men from the boys in loudspeakers. The bass energy of the kick drums will either reward you with an adrenaline surge or have you covering your ears from the horrible sound of woofer bottoming just before it plays for the very last time. Of course this isn’t a problem for my reference speakers but I wanted to see just how far the A1400-8 could push them and get their four 10” high excursion subwoofer drivers moving. The A1400-8 delivered thunderous bass response with aplomb. The transient response was lightening quick, extracting all of the decay of the kick drums, making it feel more like a live performance in my own theater room than listening to an actual recording. The wood percussion instruments were delicately reproduced with all of the subtle nuances preserved. In comparison to my Denon POA-A1HDCI, I felt the Axiom amp was a bit more lively and crisp but the soundstage on the Denon seemed a bit wider and more open.

Regardless of how loudly I played the A1400-8, it sounded effortless and unstrained revealing excellent sustain and decay of the kick drums and percussion instruments. In fact it wasn’t until I really cranked up the volume that the bass differences between the two amps became more apparent with my preference leaning more towards the Axiom’s “quicker” more “lively” rendering.

CD: Dianne Reeves Never Too Far

When I want a quick reference for gauging accuracy in bass response of loudspeakers and even amplifiers, I turn to this CD. The bass in track in Track #2 “Never Too Far” will sound muddy or weak on an improperly set up or inadequate system. I have this song pinned into my head as to how the bass should sound so I wanted to directly compare two amplifiers. A back and forth comparison between these amplifiers on my reference speakers revealed that the Axiom amp was a bit leaner in the bass department but much tighter and more lively. The decay of the bass drum was so detailed that it sounded stereophonic to me when listening on the A1400-8. I couldn’t help but to really punch up the volume and give my speakers the workout they’ve been waiting for. Track #3 “Come In” again revealed the Axiom’s very well mannered bass response with less apparent overhang that I was hearing on my reference amplifier. However, I did feel that the Denon was offering up a slightly smoother, more spacious top end. Ironically when I switched over to my bookshelf speakers to make the comparison, I conversely preferred the bass I was hearing from the Denon amp which seemed fuller to me. Perhaps on smaller less bass capable speakers, I was preferring the warmer sound the Denon amp was offering. It’s also possible that the Axiom amp preferred the lower impedance (dips to 2 ohms) of my tower speakers over my 8 ohm bookshelf speakers. Needless to say the sonic differences between the two amps thus far were subtle but noteworthy. The A1400-8 reminded me how far Class D amps have come and really shattered my misconception of them for full range high fidelity audio applications. Until I heard this amplifier, I was unconvinced that Class D would ever be a serious contender against good old fashioned linear designs.

CD: Special EFX - Collection

This is an old favorite of mine not only because of the excellent musical content, but of the pristine fidelity that really helps gauge a system’s frequency range. On track #2 “Jamaica, Jamaica”, the

triangles seemed to spread out beyond the plane of the speakers on both amps with perhaps a bit more 3-dimensional depth on the Denon amp. While I thought I heard slightly better separation of the instruments on my Denon amp, the Axiom sounded more vivacious. On the A1400-8, the plucks of Chieli Minucci’s guitar seemed more vibrant while the bass was also snappier, especially at higher listening levels. In contrast, switching over to my Decimo speakers had me preferring the (dare I say?) more sluggish bass response of the Denon amp that made those little bookshelf speakers sound more grandiose.

Track #5 “Udu Voodoo” seems surreal as I got lost in the textures of the percussive instruments and the ping-pong effect between the front speakers that the A1400-8 conveyed. Self-restraint with the volume control became quite difficult for me as the sound was just effortless at all power levels. My T30-LSE’s simply craved the unadulterated power that the Axiom amplifier was providing. The A1400-8 was proving it was right at home with the rich and complex textures of jazz music, which dominates much of my listening preferences.

CD: Randy Johnson – Hit & Run

Opening up with track #1 “Down Time”, the A1400-8 did a fabulous job of transporting me into an intimate jazz cellar enjoying a nice Brandy sniffer with my foot tapping to some funky Jazz you simply can’t find on terrestrial radio these days. The snare rolls popped right out at me providing a very bold, in your face experience typically only heard at live events. Track #4” The Hat Man” had me putting on my Fez in no time. This CD sounded absolutely fantastic on both amplifiers and at this point it was really about splitting hairs; at times I felt the depth of the soundstage favored the Denon amp while the Axiom got the nod for more boldness and vibrancy.

Miscellaneous CD’s

I ran through a gamut of CD’s and SACD’s during my listening sessions and took notes on the stuff that stood out the most to me. Listening to the Lee Ritenour & Larry Carlton duo, particularly “Remembering JP” really showed off the A1400-8’s abilities to faithfully playback dynamic program material. Percussive instruments were explosive on this amp giving you that “better than being there” experience I always seek out on the very best equipment that I review. I spent a good deal of time listening to a few tracks on an Usher CD sampler that was handed to me at the CES trade show a couple of years back. In particular track #6, “Don Juan,” revealed the superb transient bass response of the A1400-8 in droves. The guitar strumming attack and decays were simply mind-boggling. I felt like the bongos had more pop to them on the A1400-8 then they did on my POA-A1HDCI amplifier but the separation between the shakers seemed a bit wider on the Denon amp.

I threw on some bass-heavy techno type music from the likes of Depeche Mode and Roger Powell. “Only When I Lose Myself” is one of those Depeche Mode mixes that they brilliantly spin a CD off the hit single with remix options some of which work while others don’t. The “Gus Gus Longplay” is pretty trick so I went with that. The bass in this song is extremely deep and highly distorted. On most systems it sounds like mud and will easily send wimp woofers on a trip past their excursion limitations. I was expecting the Axiom amp to walk all over my Denon amp on this song but I was instead thrown a curve ball. I preferred the looser more bass heavy presentation that the Denon was portraying. The bass seemed a bit thin on the Axiom amp but ultimately it could have also been rendered more accurately as a result. On track #2 “Fallout Shelter” of Roger Powell's Fossil Poets, the Axiom amp was my preferred amplifier of choice. It loved to just belt out the power. On the Axiom amp, the bass seemed to have better control and the sound was just insanely dynamic. I had the volume cranked so ridiculously loud that I actually saw the mids in my T30-LSE’s moving from nearly 18 feet away. In nearly three years of owning these speakers, I don’t think I’ve ever driven them this hard. I was pleased to not only see the Axiom amp’s effortless ability to do this but with my speakers’ willingness to accept the power and not suffer from audible compression or distress.

DVD: Genesis - When in Rome

Its no secret that I’m a huge Genesis fan. I take all eras but really prefer the late 70’s post-Gabriel musical period of their career. Luckily, when Genesis reuinted in 2007 they played a lot of program material from that era. Hearing the opening track of Duke in full 7.1 at reference levels was to put it mildly, an energizing experience. The powerful cord progressions of Tony Banks keyboards and drum rolls of Chester Thompson and Phil Collins were perfectly rendered, sounding as good as I’ve ever heard on my reference system. “In the Cage” medley is a must-listen track for all true Genesis fans despite its nearly 18-minute length. With the A1400-8 powering my system, 18 minutes never felt so good. At all power levels, the A1400-8 delivered pristine sound, a large surround envelope and just begged to flex its muscles to remind me it was on call to deliver everything the wall outlet was capable of providing.

DVD-Audio: Beatles Love

Track #1 “Because” has become one of my favorite Beatles tunes as it really exemplifies the uncanny melodic nature of the Beatles that few if any bands today can match. I was immersed in the wonderful voices of The Fab Four. It reminded me of being at the actual LOVE performance by Cirque du Soleil in Vegas only it sounded much better in my own theater room. The A1400-8 seemed like an infusion of octane boost to my system when playing back tracks #5 “I am the Walrus” and #10 “The Benefit of Mr. Kite”. The bass peaks seemed bolder than I’ve experienced on my very own reference amp while the vocals were anchored and, although a tad analytical sounding at times, extremely clear. I was quickly realizing the A1400-8 was equally comfortable driving two or seven channels at listening levels beyond my ears’ capabilities without introducing graininess or mushy sound similar to what I’ve heard from lesser-designed amplifiers.

Recommendations for Improvement

As good as the Axiom A1400-8 multi-channel amplifier is, it could stand some improvements to make it even better. My experience with this amplifier has led me to believe this is NOT a field tested design for the following reasons:

• It’s too wide - The A1400-8 is unfortunately about ½” too wide to fit into a 17” shelf of a standard rack mount. This was an unfortunate oversight made by Axiom so be mindful of where you plan on installing this amplifier.

• Lots of internal wires instead of short low impedance returns to the power supply increases susceptibility for ground loops via unbalanced connections and also limits the channel to channel crosstalk performance. Axiom claims they’ve since then installed a low impedance grounding bar across all the speaker returns to eliminate this problem.
• Sensitivity to heat. Due to the precision internal clocking this amplifier needs to be installed into a cool location. I found when I had it about 6 inches above my Denon linear amp, the internal fan of the A1400-8 would often come on even during idling conditions. This was slightly audible at very low listening levels about 15 feet from my rack. It’s best to keep this amp away from heat generating sources.
• It’s more susceptible to damage under negligent usage than most conventional amplifiers.
• Aesthetically this amplifier doesn’t really stand out or scream high end. Its diminutive size is partly the reason, but I think Axiom could have dressed it up a bit by perhaps adding LED backlighting to the front panel logo. Personally I always go for function over form but in this market many audiophiles chose quite the opposite when selecting their products.

I completely destroyed the first sample Axiom sent me when I was doing a power sweep test and forgot to attach a test load. Once my test gear reached 20kHz, the unloaded amp hit a resonant peak (caused by the unloaded output filter) and blew up the output devices and zobel networks. Luckily Axiom had the foresight to design the amplifier to self contain the fire as I was in no immediate harm, but the smell was horrific and something I hope to never experience again. Granted my scenario is highly unlikely in the real world but the lack of protection for this type of scenario was a bit unsettling to me.

I managed to test my second unit without incident until I was swapping cables in my sound lab. I was comparing the Axiom A1400-8 and my Denon POA-A1HDCI amp on a pair of my bookshelf reference speakers while also switching over to my reference towers. Everything was fine until I decided to bi-amp my towers and move the cables over with both amps turned on. I never recommend this but as a reviewer trying to switch out as quickly as possible for the most accurate results, I got a bit reckless and took the risks for the benefit of our readers. On my towers, I had the Axiom A1400-8 powering the subs. As I switched over my live speaker cables from my Denon amp to the mid/tweet portion of my towers, I heard a loud popping sound and saw sparks come off the speaker cable and terminal lug of my speakers. I looked over to the rack and both amps were still on and no smoke or smell was evident. My speakers were also perfectly fine, no damage to any of the drivers! However, channels 5 and 6 of the Axiom amp were now dead. I have no idea what happened here but from my experience of accidentally shorting amplifiers out when powered on, they typically shut off and protect themselves. The user manual also warns that if this amplifier is shorted when outputting 200 watts or greater, serious damage will occur.

In speaking with Axiom, they informed me that since this amp has an unusually high switching frequency, it’s difficult to protect it from fault conditions without compromising sound quality. They could have very easily implemented the same current limiting protection that others such as B&O utilize but the performance tradeoffs simply weren’t worth the trade-off in fidelity. The reported failure rate on this amplifier is very low and I am certainly an unusual user but hopefully the technology will soon be available to have uncompromised protection for such circumstances. In the meantime, make sure the amplifier is always turned off when swapping out cables and don’t let anyone run sweep tones through your amp with no load attached.