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boXem Arthur 4222/E1 Amplifier Review

Rate this amplifier:

  • 1. Poor (headless panther)

    Votes: 8 2.2%
  • 2. Not terrible (postman panther)

    Votes: 11 3.0%
  • 3. Fine (happy panther)

    Votes: 61 16.6%
  • 4. Great (golfing panther)

    Votes: 288 78.3%

  • Total voters
    368

Keened

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Does NAD use a different firmware?
Link


They mention "feathering" towards the maximum peak and I don't think I see the same behavior in the graph here, but different scales, etc.


I imagine they would certainly have more freedom with their insurance policies to use custom firmware and take responsibility for the results. It could be a weighting discrepancy as well, is the power/distortion A-weighted at ASR?
 

dlaloum

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Thanks very much @amirm for this review, and particularly - thank you for including the 2 ohm measurements...

It would be really great if a 2 ohm measurement were done regularly for amp tests.... to many, they won't be relevant, as their speakers don't require it.... but there are many of us with "difficult" speakers.... and the 2 ohm measurements tends to separate the wheat from the chaff, under those circumstances! (and for those needs.
 
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amirm

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Thanks very much @amirm for this review, and particularly - thank you for including the 2 ohm measurements...

It would be really great if a 2 ohm measurement were done regularly for amp tests....
My pleasure. I could do 2 ohm here because it is one channel so I could combine my 4 ohm loads. This load box cost me some $600 to build and good weekend worth of work. So not cheap to build another for stereo testing. :) If all we want is pure power rating, then it is cheap to do. Having high-performance load with ultra-low (load) distortion is what makes it expensive.
 

Matias

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dlaloum

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My pleasure. I could do 2 ohm here because it is one channel so I could combine my 4 ohm loads. This load box cost me some $600 to build and good weekend worth of work. So not cheap to build another for stereo testing. :) If all we want is pure power rating, then it is cheap to do. Having high-performance load with ultra-low (load) distortion is what makes it expensive.
In a perfect world....

But I would be very happy even with a single channel 2 ohm measurement as shown here.... there are just so many (vast majority) of amps where the power output just collapses dramatically below 4 ohm - and specs or measurements at 2 ohm are mostly "unobtainium"
 
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amirm

amirm

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In a perfect world....

But I would be very happy even with a single channel 2 ohm measurement as shown here.... there are just so many (vast majority) of amps where the power output just collapses dramatically below 4 ohm - and specs or measurements at 2 ohm are mostly "unobtainium"
That is very feasible so will do.
 

tomchris

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A fine minimalistic monoblock from BoXem | Audio with AudioSense feature and the power button on the back.

Performance looks great - as expected. The Hypex power supply lacking 70V is a known issue. Both Hypex and Purifi have yet to release a SMPS outputting 70V. Although, I do believe that Micro-Audio has SMPS capable of >70V available...

I would have preferred that the slotted holes on the backplate were relocated to the sides, giving binding posts, power button, switches, inputs etc. much needed space to "breathe". I understand multi-channel amplifiers' adherence to this standard due to the lack of space, but 19mm spacing between binding posts on monoblocks with a capability of outputting >500W in 2 Ohm just seems wrong.

Nitpicking
------------
- ETI binding posts with larger spacing + Neutrik SpeakON Connector as an added feature
- slotted holes on the sides instead of backplate - lending more backplate space to text, binding posts, inputs etc.
 
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Garrincha

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The many simple connectors, especially on the Purifi module, do not give me a good indication that the measured values can still be achieved after years. I would prefer such a Purifi mono block design: T+A M200 assembly video

According to the German trade press, currently the best sounding Purifi implementation.
T+A surely makes nice products, alas the prices, it's 3900€.
 

JPA

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In a perfect world....

But I would be very happy even with a single channel 2 ohm measurement as shown here.... there are just so many (vast majority) of amps where the power output just collapses dramatically below 4 ohm - and specs or measurements at 2 ohm are mostly "unobtainium"
I am planning to run 4 Ohm subs in parallel in the near future, so I would also like to see 2 Ohm measurements.
 

Garrincha

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Who voted not terrible? :facepalm:
This is the top 10 best performing (in terms of SINAD) amplifier that we have measurements for...not to mention 4th best reviewed by Amir so far.

Courtesy of @Matias spreadsheet
Great amp! And I like the list of @Matias, especially the graphs of price vs SINAD, really no correlation there, similar to the Harman graphs for headphones. Audio gear is just crazy.
 

dlaloum

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OK, I take that back. I have to think of whether there is a risk of damage to amplifiers first....
Relevant point - many amps, with less than optimal self protection, might tend to "let out their magic smoke"....

Which could be a less than ideal thing to happen to various people's loan gear!

Quad used to advertise their amps as "unconditionally stable into any load"

Others specify the range of impedances that their amps can handle.... but then most of the ones in this category specify 4ohm as the lower end of their range... which is a bit silly, given that almost all 4 ohm speakers go well below 4 ohm!

But yeah - this can be within the problem zone where smoke and flames can get involved
 

alex-z

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OK, I take that back. I have to think of whether there is a risk of damage to amplifiers first....
That itself is a valid test IMO. If an amplifier rated for 4 Ohms becomes damaged by a brief 2 Ohm load, that indicates malfunctioning overcurrent protection. Your tests have shown some "8 Ohm" speakers have minimum impedance in the 2-3 Ohm range.

Even worse would be a user who experiences a short due to loose wiring, bad OCP would be an outright safety concern at that point.
 

Rja4000

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My pleasure. I could do 2 ohm here because it is one channel so I could combine my 4 ohm loads. This load box cost me some $600 to build and good weekend worth of work. So not cheap to build another for stereo testing. :) If all we want is pure power rating, then it is cheap to do. Having high-performance load with ultra-low (load) distortion is what makes it expensive.
Would that work with cheaper loads for one channel ?
You'd have to measure one channel after each other (or just stick to one), but that would remain with 2 channels loaded...
 
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amirm

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That itself is a valid test IMO. If an amplifier rated for 4 Ohms becomes damaged by a brief 2 Ohm load, that indicates malfunctioning overcurrent protection. Your tests have shown some "8 Ohm" speakers have minimum impedance in the 2-3 Ohm range.
That is fine and good but what about the owner who now has a broken amp? If this were a product company sent and was rated at 2 ohm, I could do that but not otherwise.
 
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amirm

amirm

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Would that work with cheaper loads for one channel ?
For one channel, I can combine my loads like I did here and make high-performance measurements. It is stereo version of that which is problematic.
 

Rja4000

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For one channel, I can combine my loads like I did here and make high-performance measurements. It is stereo version of that which is problematic.
Sure, but, as you say, just a dirty load is cheap.
So why not, for this very 2 ohm test, have a "dirty" load for the second channel ?
It still makes sense to measure with 2 channel loaded, doesn't it ?
 

dlaloum

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If the lights don't dim when testing at 2 ohm.... you aren't doing it right.... mwahahaha !!:p
(cue scene from young frankenstein...)

Young Frankenstein sml.jpg
 
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amirm

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If the lights don't dim when testing at 2 ohm.... you aren't doing it right.... mwahahaha !!:p
Well, that is another problem for stereo 2 ohm testing. Folks will complain about voltage sags and such.....
 

pogo

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This equates to in excess of 600 watts into 2 ohms.
That seems to match up well with the last chart here: Link

The NAD M33 seems to have a very good power supply section and use the capabilities of the first purifi design well. There is even still headroom:
Dynamic power (<1% THD, 2ohm): 815W
 
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