boXem Arthur 4222/E1 Amplifier Review

[boXem]

An error...

Edit: hmm they are using the higher voltage PSU, the Hypex SMPS1200A700 is 85V. So maybe it is correct then.

Absolute Max voltage is 75 V. The module will shut down with 85 V.

It does not only depend on the PSU, see also my post #194 & #271.

Here is a good example with the 1ET400A:
The Dali Kore have an impedance minimum of 3.3Ohms at 65Hz. Considering that these are usually driven with four bridged NAD M23, that's quite a feat for any Purifi module. In bridge mode this impedance is halved for the Purifis, i.e. 1.65ohm and seems to work well in real life (pictures of setup)

With appropriate implementation, the 1ET7040SA should also be able to do more than 950W @ 2ohm.

Knowing how you are interested in Purifi implementations, it's a pleasure to see how involved you are in this thread. I guess that's because you really like our amplifier and I have to admit that this is quite flattering.
I also see that you are quite interested in short circuit detection mechanisms that could limit the output power. If you wish to discuss the subject via MP, feel free to contact me, it will be a pleasure to share with you my experience on the matter (I was "Mr. self diagnostics" during my 20 years of work with aerospace and automotive electronics).

 

[Haskil]

Absolute Max voltage is 75 V. The module will shut down with 85 V.


Knowing how you are interested in Purifi implementations, it's a pleasure to see how involved you are in this thread. I guess that's because you really like our amplifier and I have to admit that this is quite flattering.
I also see that you are quite interested in short circuit detection mechanisms that could limit the output power. If you wish to discuss the subject via MP, feel free to contact me, it will be a pleasure to share with you my experience on the matter (I was "Mr. self diagnostics" during my 20 years of work with aerospace and automotive electronics).

Why do I want to laugh with you Boxem? However, it suffices to read the documents that you have given, the explanations that you have provided to understand at least two or three things: you need a power supply that delivers sufficient voltage and that is reliable and safe for the user, fully protected terminal blocks - Speakon for example -, and sufficient cooling of the modules to be able to draw the possible power from this purifi module according to the technical documents of the brand of this purifi module...

 

[Rick Sykora]

An error...

Edit: hmm they are using the higher voltage PSU, the Hypex SMPS1200A700 is 85V. So maybe it is correct then.

The Apollon website claims they are using the Hypex A400 so their (short burst) power specs should be very comparable to the Boxem unit in this review. There may be some error tolerance, but not so much as to get them to the advertised ones. They are clearly claiming the ones at the higher rail voltages and the A400 does not get them there. See @KMO earlier post in this thread for reference.

 

[KMO]

Yeah, I'm assuming Apollon just put up the module power ratings - I don't see how they'd be achieving them in their assembly.

The pages are inconsistent - the PET950 monoblock says it's using the A700, while the stereo says it's using the A400.

The A700 wouldn't work at all, and the A400 won't give those power numbers. (If it was that easy to get those power numbers we wouldn't be having this discussion).

 

[Rick Sykora]

Yeah, I'm assuming Apollon just put up the module power ratings - I don't see how they'd be achieving them in their assembly.

The pages are inconsistent - the PET950 monoblock says it's using the A700, while the stereo says it's using the A400.

The A700 wouldn't work at all, and the A400 won't give those power numbers. (If it was that easy to get those power numbers we wouldn't be having this discussion).

About the PET950 monoblock power supply, I see this...

Perhaps @Matias and you found a different page?

 

[KMO]

Oops, had that the wrong way round. Stereo says it has two A700s, mono one A400.

 

[Matias]

Yes, I saw their stereo amp page. Anyway it is 2 mistakes, one in the A700 model in the stereo version, second by stating the full module power using A400.

 

[Redwine]

Who voted not terrible?
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

For dummies, why is Nad M33 measuring “far lower” that the best, is there a logical reason to this?

 

[VintageFlanker]

is there a logical reason to this?

In-house buffer boards and PSU from NAD.

why is Nad M33 measuring “far lower”

It doesn't when it comes to power. Amplifiers aren't just SINAD at 1kHz/5W/4Ω

 

[mocenigo]

In-house buffer boards and PSU from NAD.

It doesn't when it comes to power. Amplifiers aren't just SINAD at 1kHz/5W/4Ω

WHAT? DO YOU NOT BELIEVE IN THE WORD OF AL-SINAD THE PROPHET? INFIDEEEELLLLL!!!!

 

[mocenigo]

Well, since you are the voice of the consumer, you should be happy to see that the measured performance here is consistent with the one published on our site.

Vox populi, vox dei?

 

[restorer-john]

For dummies, why is Nad M33 measuring “far lower” that the best, is there a logical reason to this?

NAD are complying with FTC continuous specification requirements. NAD have to sell completed products in many markets and cannot afford to have compliance issues.

Purifi can advertise whatever BS numbers they like, true or not, as they don't sell complete, consumer purchasable products in any market, as far as I am aware. They can pass the buck to the assemblers, the OEMs etc. and get way with it.

None of that detracts from Boxem's implementation. It is one of the best, if not the best.

 

[pogo]

For dummies, why is Nad M33 measuring “far lower” that the best, is there a logical reason to this?

NAD has added a gain stage to increase its headroom so that it works better with the DSP circuits of its room-correction software and tone controls. NAD concedes that this slightly decreases the M33’s signal/noise ratio, but with careful design and premium parts, and because the Eigentakt’s S/N is so low to begin with, the noise is still inaudible.
Source: soundstagehifi.com

You cannot compare a optimized ready-made chain with a power amplifier

 

[mocenigo]

Purifi can advertise whatever BS numbers they like, true or not, […] and get way with it.

With all due respect, this is BS. They advertise the numbers of their modules which are absolutely correct. It is obvious that a device with more circuitry before and around the module will perform differently. The fact that some boutique manufacturers pass along the Purifi numbers as measurements for the completed product is BS, but not Purifi’s.

 

[Sokel]

With all due respect, this is BS. They advertise the numbers of their modules which are absolutely correct. It is obvious that a device with more circuitry before and around the module will perform differently. The fact that some boutique manufacturers pass along the Purifi numbers as measurements for the completed product is BS, but not Purifi’s.

As power amps is about power I find this BS:

It's a bloody power amp,power is it's most significant parameter,mount it on a heatsink with Rth = 0.8 K/W which is common and give me NUMBERS for continuous,I can do the calcs then and find out if it suits me.

 

[dlaloum]

As power amps is about power I find this BS:

View attachment 253071

It's a bloody power amp,power is it's most significant parameter,mount it on a heatsink with Rth = 0.8 K/W which is common and give me NUMBERS for continuous,I can do the calcs then and find out if it suits me.

A lot of the implementations (based on photos) merely bolt the board to the case... and don't bother with real heatsinks.

Which, of course, means they will never achieve much in continuous terms! I would love to see more (any?) of these mounted in traditional heatsink cases... - perhaps one side for the amp board, and the other for the power supply... - then we might start to see meaningful 2ohm figures...

 

[pogo]

I would love to see more (any?) of these mounted in traditional heatsink cases... - perhaps one side for the amp board, and the other for the power supply... - then we might start to see meaningful 2ohm figures...

Link: Like NAD

 

[boXem]

Since the end of the year comes, it is time for self inspection...

Q: What is the stupidest thing you did in 2022?
A: As a normal human, I was an idiot 24/24 7/7, but asking and reminding Amir to measure the power in 2 Ohm clearly stands out. Accelerating before passing a speed camera instead of after comes second at a long distance

 

[dlaloum]

Link: Like NAD

Yep like any of the old school amps!

They aren't all that expensive:

https://www.aliexpress.com/item/32809121578.html?spm=a2g0o.productlist.0.0.3866705b3aYU8c&algo_pvid=9edf87b8-9d8b-4783-a0f3-f3f3a5859019&algo_exp_id=9edf87b8-9d8b-4783-a0f3-f3f3a5859019-22&pdp_ext_f=%7B%22sku_id%22%3A%2264598244003%22%7D&pdp_npi=2%40dis%21AUD%21117.19%21110.17%21%21%21%21%21%402101f49916723068950904904e2dc5%2164598244003%21sea&curPageLogUid=PIUYdGDrwqoI

 

[mocenigo]

A lot of the implementations (based on photos) merely bolt the board to the case... and don't bother with real heatsinks.

Which, of course, means they will never achieve much in continuous terms! I would love to see more (any?) of these mounted in traditional heatsink cases... - perhaps one side for the amp board, and the other for the power supply... - then we might start to see meaningful 2ohm figures...

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.