Axiom Audio A1400-8 Digital Multi-Channel Amplifier Review

[gene]

Gene, I'd like to make a point of clarification in your design overview:

"It switches at a much higher frequency than most other switching amps, which in this case is between 450kHz – 500kHz."

How your worded this paragraph seemed to me to imply that they are switching in this frequency range in contrast to ICEpower's design. ICEpower in fact also switches their output stage in the similar 60kHz-510kHz range.

I agree with your subsequent statements about the advantages of this switching frequency range. It's way out of the audio band, easy to filter, and stays below the RF-generating MHz frequencies used in some class D designs.

Cheers,
Chris

Hi Chris;


According to the ICE Datasheet, their best module switches between 60kHz and 380kHz (page 7).

http://www.icepower.bang-olufsen.com/files/solutions/icepower1000aspdata.pdf

Thus as I said in my review, the Axiom amp is a faster switcher, in fact the fastest that I know about right now. Its also one of the only Class D's that can actually deliver its rated power continuously and at fullbandwidth for all loads which is something ICE cannot do.

The unfortunate downside of the Axiom amp right now is its not as bulletproof as the ICE module so you have to treat it with kid gloves which I often don't do when testing gear

 

[PaulF]

Guys, the Nuforce reference 9 series switches at about 500Khz and there are products from Huygens Audio based on the MHz Class-D modules that switch at about 1 Mhz.

Huygens specs

Huygens amps

 

[mattburk]

Great article Gene!

Can you provide a list of linear amps you consider to be the best?

Would you rank transparency as the most important quality in an amp design?

Thanks.

dito that request

 

[VladP]

I extensively discuss crosstalk in this review, show measurements and even talk about the issue I found on adjacent channels with regards to higher crosstalk. Please re-read the measurements portion of my review.

As for phase accurate, I haven't seen a Class D yet that does to 20kHz.

One important difference of this amp vs ICE is the Axiom truly delivers full power bandwidth into 4 ohm loads continuously. NO ICE module can do this.

Here is directly from B&O ICE Power 1000ASP tech specs:
Output power @ 0.2% THD + N, 10Hz < f < 20kHz, 4ohm - 1100 W

They also state that ICE Power 1000ASP is capable of generating 1000W RMS output.

That directly contradicts to what you said above. Are people at B&O lying?
I would appreciate if you provided actual data to support your claim.

 

[gene]

Here is directly from B&O ICE Power 1000ASP tech specs:
Output power @ 0.2% THD + N, 10Hz < f < 20kHz, 4ohm - 1100 W

They also state that ICE Power 1000ASP is capable of generating 1000W RMS output.

That directly contradicts to what you said above. Are people at B&O lying?
I would appreciate if you provided actual data to support your claim.

First off there is no such thing as RMS power. That in itself is a misnomer. They probably mean average power but RMS sounds more impressive.

See: http://sound.westhost.com/power.htm

Secondly the very carefully speced that to appear to be a continuous rating for the untrained observer. The spec you cited is for THD + N and not a power test per se. If you look at the graph on page 14 you will see how the amp continuous output sharply drops with frequency and even at 10kHz it can only sustain that power for around 1 sec. Page 6 also shows typical max continuous power ratings without an added heatsink.

I would venture to say this amp can probably do anywhere between 85-150wpc into 4 ohms loads continuously at full bandwidth. Of course dynamically it will deliver the full 1kwatt or more per their ratings.

While I do agree music is dynamic more than continuous, I only point out that their power ratings are a bit misleading since they are rating them unfairly against other amplifiers. That being said, please continue this discussion in a separate thread as this thread is meant to support the Axiom A1400-8 review that I did. thanks.

As for my actual test data, please check out my Pioneer SC-07 Review where I measured an ICE module (albeit a lower model but funtionally similar):

http://www.audioholics.com/reviews/receivers/pioneer-sc-07

 

[chriscmore]

Hi Chris;


According to the ICE Datasheet, their best module switches between 60kHz and 380kHz (page 7).

http://www.icepower.bang-olufsen.com/files/solutions/icepower1000aspdata.pdf

Thus as I said in my review, the Axiom amp is a faster switcher, in fact the fastest that I know about right now. Its also one of the only Class D's that can actually deliver its rated power continuously and at fullbandwidth for all loads which is something ICE cannot do.

The unfortunate downside of the Axiom amp right now is its not as bulletproof as the ICE module so you have to treat it with kid gloves which I often don't do when testing gear

While I'd argue their 1000ASP is not their best, they don't all switch in the same frequency range:

250ASP output frequency range: 70kHz - 450kHz
500ASP output frequency range: 60kHz - 510kHz
1000ASP output frequency range: 60kHz - 380kHz

My point is that similarly to ICEpower, they switch in the sweet-spot frequency range that is way above audible, easy to filter, and below troublesome RF generation.

You can in fact deliver full bandwidth rated power 24/7 through ICEpower modules if you're playing actual music or movie content. B&O argues music's peak-to-average power ratio is about 8:1, which is similar to what I measure.

If you're needing something to amplify non-transient test tones 24/7, then yes, - please - look elsewhere.

Cheers,
Chris

 

[gene]

While I'd argue their 1000ASP is not their best, they don't all switch in the same frequency range:

250ASP output frequency range: 70kHz - 450kHz
500ASP output frequency range: 60kHz - 510kHz
1000ASP output frequency range: 60kHz - 380kHz

My point is that similarly to ICEpower, they switch in the sweet-spot frequency range that is way above audible, easy to filter, and below troublesome RF generation.

You can in fact deliver full bandwidth rated power 24/7 through ICEpower modules if you're playing actual music or movie content. B&O argues music's peak-to-average power ratio is about 8:1, which is similar to what I measure.

If you're needing something to amplify non-transient test tones 24/7, then yes, - please - look elsewhere.

Cheers,
Chris

Chris I am not arguing that the ICE amp is a good amp and very dynamic. I do however think its misleading to call it a 1kwatt amp in the same breath as a traditional linear amp or even the Axiom Class D that can deliver that power continuously at full frequency.

This reminds me of the car audio spec for PMPO. ICE was originally designed for subwoofer applications and integrated audio systems. Its a compact, fairly efficient, very robust design but there are limitations to it that should be noted like any other amplifier.

I would love to use the 1000ASP to power the subs in my setup and would jump on a 2CH version if it was rack mountable and reasonably priced.

 

[Dan Banquer]

While I'd argue their 1000ASP is not their best, they don't all switch in the same frequency range:

You can in fact deliver full bandwidth rated power 24/7 through ICEpower modules if you're playing actual music or movie content. B&O argues music's peak-to-average power ratio is about 8:1, which is similar to what I measure.

If you're needing something to amplify non-transient test tones 24/7, then yes, - please - look elsewhere.

Cheers,
Chris

I note that the same or similar arguments you have used in your post are the same arguements that were used some 30 years ago.

Way back in the 1970's and into the 1980's people in audio thought the same thing. However, this was corrected when people "discovered" slewing induced distortion and phase anomalies due to limited amplifier response at upper frequencies. This is old news, it has been thoroughly tested and proven without a shadow of a doubt to where it is now accepted as a general requirement for well designed full range audio amplifiers.
Regards;
Dan Banquer

 

[gene]

The Clone Wars have begun.

 

[ohio]

Just bumping this to see if there have been any updates to this amp. As an urban dweller, I typically am limited in storage/rack space and outlet current, so this is a pretty attractive package... but based on the review still seems a touch immature as a consumer-ready product.

 

[MinusTheBear]

Just bumping this to see if there have been any updates to this amp. As an urban dweller, I typically am limited in storage/rack space and outlet current, so this is a pretty attractive package... but based on the review still seems a touch immature as a consumer-ready product.

This amp was recently taken off their website. Not sure if it is temporarily or discontinued but from accounts on various sites, it has been plagued with quality issues since its inception.

 

[TLS Guy]

This amp was recently taken off their website. Not sure if it is temporarily or discontinued but from accounts on various sites, it has been plagued with quality issues since its inception.

I'm not surprised, that unit was launched well before it was ready. If it blows on the test bench the consumer will blow it for sure.

Also the HF rise is unacceptable.

I think class D amps will have real problems driving speakers through passive crossover networks.

What axiom should have done is develop a set of active speakers, with digital crossovers. They should use class A amps for the tweeters though.

If they had done that, they would have introduced a truly innovative consumer product line.

If calls D amps are going to gain acceptance any time soon, that will have to be the route taken.

 

[MinusTheBear]

Ohio as for the small footprint, the possible issue here is your rack length. Axiom seems to have put too much obsession in the height of this unit as well. The fact the amp is too long for a standard audio/video rack shows the in field testing of the unit was poor. That should have been caught before the release because it will be problem for a lot of people.

 

[gene]

This amp was recently taken off their website. Not sure if it is temporarily or discontinued but from accounts on various sites, it has been plagued with quality issues since its inception.

The A1400 amp is a true powerhouse and one of the first Class D amps that I actually liked the sound of.

However, this amp has a lot of reliability problems. The rat nest of wires is unacceptable IMO, and something that should have been cleaned up for production units. My first unit caught on fire, the second unit blew 2 channels just swapping cables. I read of numerous returns on AVS as well.

The A1400 also doesn't fit in a standard 17" rack which is a huge oversight IMO. I pointed out all of these design flaws in my review which explains why Axiom never even linked to my review on their website and believe me it caused a severe sore spot in our relationship after it published.

As TLS points out, the HF rise should have been fixed but most importantly, they needed better fail safes on the unit.

Axiom also priced themselves out of the market IMO. I still use two of the channels to power my subs without incident but if I ever leave my home for extended periods of time, I always unplug my A1400-8.

 

[MinusTheBear]

I never understood the idea of putting to market an amp that is more expensive than their flagship speaker either. Not just by a little but A LOT. Just before this review was released there was a case where someone was swapping cables between an AVR and the A1400-8 trying to test any sound quality differences and what do you know? He blew either a channel or the receiver. So you are not the only one this has happened to.

 

[gene]

I never understood the idea of putting to market an amp that is more expensive than their flagship speaker either. Not just by a little but A LOT.

We have had that discussion many times with the fine folks at Axiom. They believe however that regardless of price, their M80's can't be beat in their own in-house Blind test, so they never saw a need to make a more expensive speaker.

 

[MinusTheBear]

As for an employee taking part in a controlled test I know I would have a very difficult time being unbiased even if done blind.

 

[gene]

As for an employee taking part in a controlled test I know I would have a very difficult time being unbiased even if done blind.

Bingo! Last time I visted Axiom they put me through their "double blind test" procedure. Prior to going they sent me a pair of M60v3s for our most recent $1k floorstanding shootout. I spent over 1 month listening to those speakers. When I sat in their blind test, I identified the M60s everytime. I know the sonic signature of an Axiom speaker since I've listened to it so extensively. Listening blind doesn't remove that bias.

 

[MinusTheBear]

Another problem with using employees along with being able to pick out their own speaker in a blind test is the ability to bias the subjective listening scores. It would be very easy to score a speaker much better if you could tell the other speaker was clearly awful, but in the case where one is better you can always score them to be similar to avoid offending your employer. Your speakers can never lose.

 

[gene]

Another problem with using employees along with being able to pick out their own speaker in a blind test is the ability to bias the subjective listening scores. It would be very easy to score a speaker much better if you could tell the other speaker was clearly awful, but in the case where one is better you can always score them to be similar to avoid offending your employer. Your speakers can never lose.

Hence how the term "similarly good was born". This is how most of the companies that run DBTs do it however.

Here is an example of their DBT run by their own employees: http://www.axiomaudio.com/archives/October2010.html
guess who won the comparison