boXem Arthur 4222/E1 Amplifier Review

[Sokel]

So. the 1ET400A bolted to the chassis is absolutely fine.

Of course it is,measurements show that in detail.
But it would be nice to have a guide like Ice Power does for example giving the exact test conditions.
I will never claim that even the 300a2 is a better amp,is just nice to have some data to guide you.

 

[caught gesture]

Longevity of the electronics is important to someone like me who is still using “old” technology that just keeps working after almost two decades. The casework on what I have is all lovely aesthetics, but I’d happily compact the components and hide them away. I’ll replace when what I have starts to fail. It’s wonderful that I’ll be able to replace with cheaper, that measures better, and consumes less power. Longevity will still be a concern to someone like me who places a high value on sustainability, ie, what I have is good enough if optimised and knowing the limits of my ageing hearing!

 

[mocenigo]

Of course it is,measurements show that in detail.
But it would be nice to have a guide like Ice Power does for example giving the exact test conditions.
I will never claim that even the 300a2 is a better amp,is just nice to have some data to guide you.

True. That would be nice. I think we could suggest it to Bruno, Kim Madsen and Co. They usually reply with the correct info if asked. So writing it down shouldn’t be difficult for them.

 

[mocenigo]

Longevity of the electronics is important to someone like me who is still using “old” technology that just keeps working after almost two decades. The casework on what I have is all lovely aesthetics, but I’d happily compact the components and hide them away. I’ll replace when what I have starts to fail. It’s wonderful that I’ll be able to replace with cheaper, that measures better, and consumes less power. Longevity will still be a concern to someone like me who places a high value on sustainability, ie, what I have is good enough if optimised and knowing the limits of my ageing hearing!

100% ACK

 

[dlaloum]

If I wanted to buy one I would buy one with heatsinks. However up to 10-20W continuous the plate affixed to the chassis is fine. I consider it a perfectly linear power amp up to those power levels and with a significant headroom for transients and short bursts. If you need 400W continuous from a 400W amp, you are either listening to crappy noise or your amp is seriously underpowered because you have no headroom, hence no dynamics, and when the music has a transient the amp turns off or something bad happens. That’s why there are 3KW amps.

So. the 1ET400A bolted to the chassis is absolutely fine.

Hmm my excessive expectations for over-engineering....

I know that in continuous terms, I seldom use more than 1 W - perhaps 5 W on the very most demanding material.... and peaks would max at 128W or thereabouts.... (at 8 ohm equivalent) - but those peaks do imply a 2 ohm max of 512W)

My current ClassD amps are rated at 1200W@2ohm... Crown XLS2500... the Fans have never spun up... and the internal "heatsinks" - are negligible

So in terms of "reason" and "logic" - the heatsinks are unnecessary over engineering.

Here is the counter argument:

Class D amps are complex beasts, lost of tiny surface mounted components - difficult and expensive to repair at the component level - most repairs are achieved by replacing entire boards.

My 40 year old Quad 606 can be economically refurbished when it needs it (every 20 to 30 years?)

The Class D amps.... well their lifetime is likely to be between 10 and 15 years - after which they are probably junk, as their boards will no longer be available as spares/replacement parts...

If they are over-engineered in terms of heat-sinking - and kept at substantially lower average temperature for the components - their lifetime is likely to be substantially increased - potentially doubled or more.

Silicon component lifetimes tend towards a logarythmic curve when related to temperatures... yes they can run perfectly well without additional heatsinks... but drop the average temperature by 5C and you might find that the lifetime is doubled.

Just my 2c / thoughts

 

[Gremlins]

Tested this week end ( saturday and sunday) boxem purifi Vs AUDIOPHONICS HPA-S400ET purifi at 1490e for stereo set up. Speakers were technics sb g90 and JBL L100 classics

Listening room has a good amount of treatment, source was qobuz via lumin



We were 4 folks and did lots of ABX listening

Conclusion : impossible to determine which amp was playing, period


Boxem was nice looking, so was the audiophonics that was over my expectations to say truth

 

[Matias]

@boXem how much power at 4 ohms 1% THD+N would a pair of 1ET7040SA give using a single SMPS1200?

 

[VintageFlanker]

@boXem how much power at 4 ohms 1% THD+N would a pair of 1ET7040SA give using a single SMPS1200?

Probably the same as a pair of 1ET400A using a single SPMPS1200, or less...

 

[boXem]

@boXem how much power at 4 ohms 1% THD+N would a pair of 1ET7040SA give using a single SMPS1200?

In 4 Ohm, both the 1ET400A and 1ET7040SA are limited by the supply rails. So they have the same behavior with the same power supply. 380 W / 400 W burst.

 

[Fidji]

In 4 Ohm, both the 1ET400A and 1ET7040SA are limited by the supply rails. So they have the same behavior with the same power supply. 380 W / 400 W burst.

i have currently 1et400 stereo with single smps1200 psu.

what would be the difference between this and 2 of your 1et7040 with smps1200 each?
at 2ohm, electrostats.

 

[VintageFlanker]

what would be the difference between this and 2 of your 1et7040 with smps1200 each?
at 2ohm, electrostats.

Twice the power.

 

[Fidji]

Twice the power.

This are my speakers [DYI measurements done by fellow enthusiast], so as expected from Electrostats. I have the impression of slightly rolled-off treble. Currently driving them with Audiophinics 1ETA400a stereo amp with single SMPS1200 PSU

@boXem specs his stereo !ET400 amp with single PSU as follows
In Arthur 4215/E2, the amplification stage can deliver up to 210 W in 8 Ω and 450 W in 2 Ω

and 1ET7040sa monoblock with the same PSU for 1 channel, which seems fair with less than optimal PSU
In Arthur 4222/E1, the amplification stage can deliver up to 210 W in 8 Ω and 700 W in 2 Ω

Am I right, assuming, 700W vs 450W and 40A vs 25A, that roll-of between 7-10kHz should be reduced by around 2dB?

Thanks in advance.

 

[boXem]

This are my speakers [DYI measurements done by fellow enthusiast], so as expected from Electrostats. I have the impression of slightly rolled-off treble. Currently driving them with Audiophinics 1ETA400a stereo amp with single SMPS1200 PSU

View attachment 294204

@boXem specs his stereo !ET400 amp with single PSU as follows
In Arthur 4215/E2, the amplification stage can deliver up to 210 W in 8 Ω and 450 W in 2 Ω

and 1ET7040sa monoblock with the same PSU for 1 channel, which seems fair with less than optimal PSU
In Arthur 4222/E1, the amplification stage can deliver up to 210 W in 8 Ω and 700 W in 2 Ω

Am I right, assuming, 700W vs 450W and 40A vs 25A, that roll-of between 7-10kHz should be reduced by around 2dB?

Thanks in advance.

Missing power means clipping. With these amps, clipping is not heard like something missing, it's really dirty. So I do not believe that the impression you have is linked to a lack of power.
The advantage of getting more power is to be able to listen louder before clipping. When the max power doubles, you can play 3 dB louder. But before clipping, both amplifiers will behave the same

 

[RandomEar]

I have the impression of slightly rolled-off treble.

Honestly: Before randomly spending 1000 $++ on a new amp, why not get a UMIK 1 for 80 $ (or even less used) to confirm that you are actually missing treble response? If that is the case, it might still not be related to your current amplifier, but at least you will then have the tools to narrow it down.

 

[Fidji]

Missing power means clipping. With these amps, clipping is not heard like something missing, it's really dirty. So I do not believe that the impression you have is linked to a lack of power.
The advantage of getting more power is to be able to listen louder before clipping. When the max power doubles, you can play 3 dB louder. But before clipping, both amplifiers will behave the same

Thanks a lot for your reply. Indeed my previous experience was either with tube or A/B class of amplifiers, where underpowered amp manifested itself as gradually increasing treble roll-off, but without going into some nasty clipping.

EDIT: I am using DRC and above transition frequency my goal is to have as symmetrical L-R as possible, working not towards some target curve, but so calle "according to L_R" mode of Trinnov. In order not to get into clipping, I am limiting Trinnov to +0/-3dB above 4kHz. If I do not get into clipping now, with 1ET400, I think I can go to +2/-3dB and get them 100% aligned. OCD, I know. But Trinnov charts look much nicer then.

Honestly: Before randomly spending 1000 $++ on a new amp, why not get a UMIK 1 for 80 $ (or even less used) to confirm that you are actually missing treble response? If that is the case, it might still not be related to your current amplifier, but at least you will then have the tools to narrow it down.

I do need 3 extra channels anyway for my HT. I have Umik1 and Umik2 and REW is my trusted companion [as it should be with 9.6.7 setup]. There is some roll-off, and I would expect, based on other measurements available [e.g. in Stereophile], that the speakers should be rather on the bright side. Let's see.

 

[egellings]

This is a review and detailed measurements of the boXem Audio Arthur 4222/E1 mono power amplifier. It was sent to me by the company and costs €1,490.00.
View attachment 234484
The design is quintessential European with gray body and colorful front panel which I like. The only power button is on the back:
View attachment 234485
Fortunately you have trigger input so you can set it to power up when the source turns on. Three gain settings are provided which is very nice. Unlike some amps in its class, it has both XLR balanced and RCA unbalanced inputs.

The amplifier is class D and is based on Purifi 1ET7040SA module.

EDIT: amp is 4222, not 4215.

boXem Arthur 4222/E1 Measurements
I started with the input gain set to low:
View attachment 234486

This is superb performance and easily lands the unit in our top 5 amplifiers ever tested:
View attachment 234487
To get to full power with low gain, you need 9+ volts of input. So I set the amp to medium gain where 4 volts is enough to push it into clipping. Performance thankfully remains the same:
View attachment 234488

Signal to noise ratio is exceptional:
View attachment 234489

Low distortion translates into very high distortion-free dynamic range:
View attachment 234490

Frequency response is load independent and quite flat in audible band:
View attachment 234492

There is healthy amount of power available into 4 ohm:
View attachment 234493
View attachment 234494

Company asked me to also test 2 ohm performance:
View attachment 234495

We get the same low noise and distortion into 8 ohm:
View attachment 234496

There is some "ballooning" of the distortion curve at higher frequencies:
View attachment 234497

As noted, this is still very good for class d amplifier.

Conclusions
Building on solid foundation of Purifi amplifier module, the 4215/E1 delivers the goods with tons of power with very low noise and distortion. And it does so in a compact and attractive box with nice feature list. Not sure what else there is to ask for. Yes, the price is a bit high but you are getting European build and support so you need to value that as well.

It is my pleasure to recommend the boXem Arthur 4222/E1 amplifier.

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As always, questions, comments, recommendations, etc. are welcome.

Any donations are much appreciated using: https://www.audiosciencereview.com/forum/index.php?threads/how-to-support-audio-science-review.8150/

It's mono, so you need one for each ear.

 

[dlaloum]

Missing power means clipping. With these amps, clipping is not heard like something missing, it's really dirty. So I do not believe that the impression you have is linked to a lack of power.
The advantage of getting more power is to be able to listen louder before clipping. When the max power doubles, you can play 3 dB louder. But before clipping, both amplifiers will behave the same

Typically lack of power / clipping refers to V limitations, how do they behave when the limitation is not V but A (Current)?

 

[Fidji]

Honestly: Before randomly spending 1000 $++ on a new amp, why not get a UMIK 1 for 80 $ (or even less used) to confirm that you are actually missing treble response? If that is the case, it might still not be related to your current amplifier, but at least you will then have the tools to narrow it down.

Krell vs 125W Tube Amp (3x different driver tubes) , Martin Logan hynrid electrostats (same as mine)
(Measurements not mine, have permission to post them) Krell is bpthe blue line.

 

[dlaloum]

What is the speakers impedance / phase to frequency profile?

Are we seeking the result of a hard to drive high end? (impedance dropping as frequency rises?) - hence the krell providing more high end extension vs the tube amps? (due to the tubes hitting current or impedance driving constraints before the krell does?)

 

[Fidji]

What is the speakers impedance / phase to frequency profile?

Are we seeking the result of a hard to drive high end? (impedance dropping as frequency rises?) - hence the krell providing more high end extension vs the tube amps? (due to the tubes hitting current or impedance driving constraints before the krell does?)

Impedance - please see tab in one of my earlier posts on this page. Yes, hard to drive speakers.

Hence my question on potential difference in response between 25A/425W@2Ohm 1ET400 and 40A/700W@2Ohm D class amp.

I have found some old measurements [they were made to test effectiveness of Trinnov DRC] and graphs are offset by 10dB, measured at 80db. Lowest [violet] is without DRC engaged. Target curve was -3dB 20khz vs 1Khz. Purifi 1ET400 stereo with single SMPS1200