# Performance Limitation of Purifi Amplifier unit and boXem Arthur 4222/E1 Amplifier

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#### thin bLue

##### Active Member
Reviewer
I commented about output power of 1ET400A and 1ET7040SA. And I could see some misleadings and errors. So i decided to start this thread.

Let's check 1ET400A first.

The current limit for the 1et400 is 25 A.
Not 15 A as one of our member boXem claims.
It is clearly stated in the data sheet.

You can cross check, My 2 Ohms 580 Watts output measure of 1ET400A based Amplifier is entirely consistent with a 25 A peak current limit in the data sheet.

P(W, Watts)
V(V, Volts)
I(A, Amps, Amperes)
R(Ω, Ohms)

P = V x I = I^2 x R
Sqrt (P/R) = I

I measured 1ET400A pushed 580W, 2 Ohms @ 1%

Sqrt (580 W / 2 Ohms ) = 17 A rms ( or 24 A peak)

24 A peak is definitely below 25 A Datasheet claims.

So, we can clearly see current limiting(so-called OCP) didn't engaged, PSU fed 1ET400A power well, do not limited any performance of Amplifier.

With 1ET400A and appropriate Power Supply Units, The only limitation factor is Heat that detected by sensors of Purifi units, which is depends on Physical Thermal capacity of complete Amplifier, unless hit OCP engages @ 25 A.

With this graph, one of our member claimed 1ET400A's limits are 450 W @ 2 Ohms / 15 A of current.

Quite often the Company like Purifi need to write strict numbers in their spec-sheet like 450 W. But, they brightly printed letters ~ 25 A on the first page of sheet as you saw.

Further more, you can see another page of sheet.

This means at least about 450 W Output powers are expected with right PSU.

So, Estimate limit current '15 A' from number '450' is completely misread of data.

Especially, company owners are responsible to provide correct information about their own products. Wrong informations must correct immediately at the moment Company recognised.

Claiming "15 A is the point OCP engages" as someone from Internet and Claiming "15 A is the point 1ET400A's OCP engages" as Company owner is completely different game.

Most of limits of Purifi-based Amplifiers are determined by how it is designed and implemented.

Like,
How to feed the signal to Purifi unit
How to feed the power to Purifi unit
How to cool the Purifi unit

Then, Let's see 1ET7040SA.

This is the same graph in the 1ET7040SA datasheet. The graph indicates PSU of Arthur 4222/E1 Amplifier is running at about 61 volts (700 W @ 2 Ohms) instead of the 1ET7040SA's originally rated 70 volts (to produce 950 W @ 2 Ohms).

It also mean 61 V PSU will get way higher THD+N at same output power like 700W than 70 V PSU.
(THD+N : the lower the better)

Compare to well powered 1ET400A(580 W)
700 W Arthur 4222/E1 is near to 1ET400A(120 W less than 700 W) instead of 1ET7040SA's rated power(250 W more than 700 W).

And 1ET400A has better SINAD than 1ET7040SA.
So, If you decide to use 1ET7040SA, it is better to set it to sufficient power to get enough gain not marginal.

If you decide to build of get Purifi-based amplifiers, Do you want to limit the performance with PSU or Amplifier Unit itself?

Still Arthur 4222/E1 Amplifier is nice Amp at absolute scale. Most of Amplifiers on the market has worse performance than Arthur 4222/E1 Amplifier.

But as Point of view of Purifi-based applications, That's much less than Purifi Units own capabilities. Arthur 4222/E1 Amplifier could do better with little more efforts.
1ET7040SA can do more, so 1ET7040SA based Amplifier could do more, too.

That is why the name 7040 is 7040.
70 V , 40 A

This is my point of view.

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#### VintageFlanker

##### Major Contributor
Forum Donor
May I ask what is the point of creating a separate thread for this?

OP

#### thin bLue

##### Active Member
Reviewer
May I ask what is the point of creating a separate thread for this?
Hi, If you see the same contents again, I need to say sorry.

My previous comments(almost same contents) in the other thread judged for 'being off topic and misleading' by moderators.

So, prevent things like that, I started new thread.

#### vicenzo_del_paris

##### Member
Forum Donor
I don't get either the point of such thread...
@boXem | audio has already explained the choice of using an SMPS1200.
He makes manufacturing choices of his own, taking into account constraints, whatever you're happy or unhappy with.

That's sad to see people to complain for anything.

Could he have used another PSU?
Maybe.
And so what?

OP

#### thin bLue

##### Active Member
Reviewer
No more off topic but still misleading.
I was exhausted by your master's debating tactics and was happy to see him banned. Won't debate with you. Bye.
You can always give your own fair opinion and exact numbers. However, Second sentence of yours can be read as really rude.
Please refrain from saying that next time.

OP

#### thin bLue

##### Active Member
Reviewer
I don't get either the point of such thread...
@boXem | audio has already explained the choice of using an SMPS1200.
He makes manufacturing choices of his own, taking into account constraints, whatever you're happy or unhappy with.

That's sad to see people to complain for anything.

Could he have used another PSU?
Maybe.
And so what?
My point.

1. Misrepresentation about the 1ET400A Amplifier Unit.

2.Just my opinion about Still Arthur 4222/E1.

------
I don't have any PSU.
Because I'm customer, not maker.

#### Sokel

##### Major Contributor
I understand that boxem made a choice according to whatever plans,limitations,research,etc.
That's not bad or good,is just a choice and people can judge by themselves.
It makes some sense though for someone going after a 1ET7040SA to expect the full (largely advertised) specs.
But as long as the boxem's implementation specs are there for everyone to see I can't see a problem.

OP

#### thin bLue

##### Active Member
Reviewer
I understand that boxem made a choice according to whatever plans,limitations,research,etc.
That's not bad or good,is just a choice and people can judge by themselves.
It makes some sense though for someone going after a 1ET7040SA to expect the full (largely advertised) specs.
But as long as the boxem's implementation specs are there for everyone to see I can't see a problem.
You are right.

I have opinion and others too. It's just humble opinion of mine.
Someone will buy, someone will not.

Nice summarisation!

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#### restorer-john

##### Grand Contributor
Forum Donor
I must have missed the review thread drama and banning (glad I did).

Bottom line is this:

Continuous power with these modules at the powers claimed will result in one form or another of thermal throttling/shutdown or current limiting. The currents we are talking about are huge, and way in excess of any sensible requirements in a home situation.

That said, if anyone wants to actually run full power continuous* tests into suitable (fan cooled) loads to determine what any of the Purifi implementations can actually achieve long term, I fully support that.

Otherwise all this "data sheet vs manufacturer vs guy with a load and a scope" is a bit childish.

* 5 minutes or more, preferably 1 hour.

#### JSmith

##### Major Contributor
The members who would be interested in understanding what is this "active common mode rejection" that we advertise, how we did to achieve a better noise level than most 1ET400A implementations while the 1ET7040SA is 40% noisier than the 1ET400A, why the power response seems to be high passed, or what is the reason behind this U-shaped buffer can of course participate to the thread.
1ET7040SA's originally rated 70 volts
Yes, but as was pointed out in the other thread a number of times, this uses the Hypex SMPS1200A400 which is quite normal and is used by most other Purifi based amps running this module... like Buckeye;
Please note: you may notice that our power ratings for the 1ET7040SA are lower than those quoted by other competitors. This is because the SMPS1200A400 power supply does not drive the 1ET7040SA to full rated power. The ratings we provide below are honest and real world. For any other competitor who also uses an SMPS1200A400 with their 1ET7040SA builds and quotes higher power output, beware.
Purifi seem to recommend the use of the SMPS1200A400;

I don't see any similar datasheet for using the SMPS1K-PFCR2 from Purifi.

From what I can see, there is no misleading information on boXem's product page? It's not boXem's fault Purifi couldn't be bothered releasing a 70V SMPS to go with their module... or maybe there is a reason they didn't. It will be interesting to see which implementations last the test of time regardless.

This seems to be a storm in a teacup to me... the 4222/E1 is a superb implementation of the Purifi module.

JSmith

#### Sokel

##### Major Contributor
It's not boXem's fault Purifi couldn't be bothered releasing a 70V SMPS to go with their module
That's odd from every angle you see it.
They make beautiful amps but they expect their competitor to power them.

#### HarmonicTHD

##### Major Contributor
Forum Donor

This is what BoXem specifies on their website. Unless I am missing something I can’t see the alleged misrepresentation in terms of power capability.

#### Jim Taylor

##### Major Contributor
Forum Donor
Some cars have a speedometer that displays up to 120 mph (almost 200 kph). Because of safety and emissions equipment, the car cannot go that fast. Not even close. If you want to race, and remove the safety and emissions equipment and hot-rod the motor, you can go far faster than 120 mph.

Does this mean that the car manufacturer misrepresented the speed potential or the motor power?

I don't think so. One trades power for safety and efficiency, and the other one gives up safety and efficiency for power. You pay your money, you buy your ticket.

Jim

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OP

#### thin bLue

##### Active Member
Reviewer
I must have missed the review thread drama and banning (glad I did).

Bottom line is this:

Continuous power with these modules at the powers claimed will result in one form or another of thermal throttling/shutdown or current limiting. The currents we are talking about are huge, and way in excess of any sensible requirements in a home situation.

That said, if anyone wants to actually run full power continuous* tests into suitable (fan cooled) loads to determine what any of the Purifi implementations can actually achieve long term, I fully support that.

Otherwise all this "data sheet vs manufacturer vs guy with a load and a scope" is a bit childish.

* 5 minutes or more, preferably 1 hour.
Yes.
The currents we are talking about are huge, and way in excess of any sensible requirements in a home situation. <- 100% agree.

It's all about, Will you accept 'Use detuned 1ET7040SA to pay full cost of 1ET7040SA and get detuned Output power' or not.

In my case not, but others can love it.

It depends on people. so..

OP

#### thin bLue

##### Active Member
Reviewer
View attachment 235086

This is what BoXem specifies on their website. Unless I am missing something I can’t see the alleged misrepresentation in terms of power capability.
You can check this comments out.

Post in thread 'boXem Arthur 4222/E1 Amplifier Review' https://audiosciencereview.com/foru...r-4222-e1-amplifier-review.37930/post-1336607

Post in thread 'boXem Arthur 4222/E1 Amplifier Review' https://audiosciencereview.com/foru...r-4222-e1-amplifier-review.37930/post-1337087

#### BDWoody

##### Chief Cat Herder
Moderator
Forum Donor
Otherwise all this "data sheet vs manufacturer vs guy with a load and a scope" is a bit childish.

Gotta agree. I don't see this being helpful.

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