boXem Arthur 4222/E1 Amplifier Review

[dlaloum]

Usually it goes into protection, I.e. it turns off.

Is that a generic comment (ie: like amps usually do x) or one specific to this one?

I have heard amps that are current constrained simply start to sound "confused" - midrange loses focus, imaging and staging collapses, and yet it seems to be working fine - at standard listening levels ie: around 72db SPL at MLP or circa 4W average to the speakers...

The same amp is known for shutting itself down when running bench tests for more than 30 seconds at 5W into a 4 ohm load.... yet into my 4 ohm nominal speakers, with minimum impedance at 1.6ohm, and crossover to the woofer dropping to 3ohm - they ran just fine at around the 4W mark (estimated - based on volume level and speaker specs) - well sort of just fine - with the confusion of the sound / reduction in sound quality.

So it wasn't enough to trigger protection circuits, but it was enough to impact sound quality - if it was on a system I was not intimately familiar with, I would have had difficulty telling that there was a problem... there are plenty of systems that under normal circumstances sound the way my own did with this amp feeding it - but on my own system I know what it should sound like, and I know that it can do better.... and swapping in one of my more capable power amps instantly resolved the problem!!

Hence I ask more questions about difficult load capabilities, and the impact of difficult loads on amp performance. (in my case I presume there was a substantial rise in some form of distortion that was messing things up, but not to the point of clipping, where distortions are shockingly audible)

 

[boXem]

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

Two cases:
1. the current limitation comes from the short circuit detection: on the Purifi modules it is very nicely implemented and the amplifier behaves like if it would be in voltage limitation.

2. The current limitation comes from the power supply being out of juice. The Hypex power supplies being non regulated, the output rails voltage will decrease, causing voltage clipping.

 

[boXem]

Usually it goes into protection, I.e. it turns off.

That is in the case when the current limitation lasts for too long. Happens at low frequencies, not high ones.

 

[Fidji]

Still it is funny - I was trying to look around for some technical data, reviews etc.

Overarching message from almost everybody, incl. producers like BoXem, Buckeye etc is that 1ET7040 is overkill and there is no need to upgrade from 1ET400. Anyway, I still can not think about anybody more suitable for this upgraded amp, than myself with infamous electrostats. [not the same model, but the same principle in treble, mine has powered bass part and x-over at 270Hz to panel]

Meanwhile I have the path to lay down my hands on one of those, so I will do and post some measurements before/after.

 

[boXem]

Still it is funny - I was trying to look around for some technical data, reviews etc.

Overarching message from almost everybody, incl. producers like BoXem, Buckeye etc is that 1ET7040 is overkill and there is no need to upgrade from 1ET400. Anyway, I still can not think about anybody more suitable for this upgraded amp, than myself with infamous electrostats. [not the same model, but the same principle in treble, mine has powered bass part and x-over at 270Hz to panel]

View attachment 294348
Meanwhile I have the path to lay down my hands on one of those, so I will do and post some measurements before/after.

In theory, you are right, the 1ET7040 is designed for such speakers. So some vendors will tell you that you need to upgrade.
But for your specific case, you do not seem to listen loud enough to need it . If you seriously crank up the volume, the SMPS1200 + 2x1ET400A will become the limiting factor.

 

[Fidji]

In theory, you are right, the 1ET7040 is designed for such speakers. So some vendors will tell you that you need to upgrade.
But for your specific case, you do not seem to listen loud enough to need it . If you seriously crank up the volume, the SMPS1200 + 2x1ET400A will become the limiting factor.

It is the other way round

I am waiting for some vendor to tell me "Fidji, you NEED to upgrade" , all I am getting is "you are cool with 1et400, nothing to see here"

 

[boXem]

It is the other way round

I am waiting for some vendor to tell me "Fidji, you NEED to upgrade" , all I am getting is "you are cool with 1et400, nothing to see here"

Fidji, you NEED to upgrade.
My pleasure .

 

[dlaloum]

LOL - indeed!! - I know that my setup runs fine with my Quad 606 power amps (which I love!) - but as "Breathless" says in Dick Tracy "I Want More!!"

So I run with the Crown XLS amps ... 1200W @ 2 ohm rather than the Quads 90W @ 2ohm.... because, just to be sure, "I want more!"

So yeah objectively the ET400 is probably ample - but the ET7040 has more peak headroom.... cos "I want more!"

 

[doug2761]

Krell vs 125W Tube Amp (3x different driver tubes) , Martin Logan hynrid electrostats (same as mine)

Terrific graph. Thanks for posting. This explains a bit my experience with electrostatics and tube amps. It seemed that I got a mellower sound with tubes as the rolled off frequency response in your graphs suggest. I could have and would have been better off with PEQ and solid state gear but that wasn't around at the time.