Review and Measurements of Purifi 1ET400A Amplifier

[MZKM]

No soldering ?

Oh man, I need to go learn how to do this, seems like something I would enjoy doing.

The original kit required soldering, but not the current kit.

 

[phoenixdogfan]

True.
Would be interesting if you measure only 1 channel of this 1ET400A amp turned on. If it can beat the single nc400 then.

Also interesting to see what the maximum power output would be if each 1ET400A were driven by a single SMPS1200

 

[Rusty Shackleford]

What does the amp’s square wave look like?

 

[amirm]

What does the amp’s square wave look like?

At what frequency?

 

[Tks]

There are exceptions. Read the 1st two posts here, and take a close look at #2's 1st photo.

Need an account :\

You'd be surprised, maybe, at how easy "good enough" soldering is... Get a soldering iron and a silly project (for practice) from the hobby store near you and try. Purists will correct me, I expect, but ...all you do is heat (by touching with your soldering tip, and holding still) the joint that you want to solder. Touch the solder to the joint itself (not to the soldering tip) and wait. The solder melts like candle wax when the joint gets hot enough to melt the solder. Done. The molten solder flows really quickly into the joint, so all you have to do is hold still for a few seconds. Lift the soldering iron when the lead flows and the joint will cool almost instantly. (Like most things, you can find a hundred good videos on YouTube.)

I've done soldering of dental prosthesis a tad a while ago. The thing is, getting a table and all the stuff for cleaning up messes and such is annoying, I also lack the electrical knowledge to be safe about the ordeal, and end up making something of this sort.

 

[pjug]

Are you able to show the high freq noise like you did for the Nord and others?

 

[Rusty Shackleford]

At what frequency?

I’d love to see a 10kHz squarewave into 8 ohms for comparison with Stereophile reviews of the NAD M22, etc.

 

[maxxevv]

No soldering ?

Oh man, I need to go learn how to do this, seems like something I would enjoy doing.

That's the satisfaction in DIY projects .... going beyond your comfort zone and getting it done!

 

[amirm]

What does the amp’s square wave look like?

I am not sure what bandwidth JA uses at stereophile. Mine is at 1 Mhz but there is an AES-17 filter in addition:

And here is JA's measurements: https://www.stereophile.com/content/nad-masters-series-m22-power-amplifier-measurements

Let me know what you learn.

 

[amirm]

@amirm could you show the wide spectrum no filter high frequency switching noise, as you did with other class D amps too? Thanks.

Added to the review. Here it is:

We see the switching frequency at 500 kHz and its second harmonic at 1 Mhz and not much else. You can also see the increased ultrasonic energy up to 100 Khz which messes up the baseline noise for THD+N when bandwidth is 90 kHz.

 

[tktran303]

The power thing, whether you choose one part of the knee or another, or at 1% THD...i think it's fine and as long as Armin is consistent.
I always look at the knee, because that's where I want my amp to be operating. I really don't want to be anywhere near 1% distortion, but
that's my preference, because I prefer to stay in the most linear region.

But we also need to relate it to hearing. 400W vs 257W @ 4ohm. The numbers like might look like a big difference.. but is it?

Not really. It's actually 2dB of "extra amplification". For reference, that's not even a click on your phone's volume button.
Some hi-fi preamps like mine adjust volume by a calibrated 1dB, so it's" just 2 clicks louder"

 

[miero]

PURIFI Audio and the Audiophile Style reader's Q&A with Lars Risbo & Bruno Putzeys
https://audiophilestyle.com/ca/bits...eaders-qa-with-lars-risbo-bruno-putzeys-r815/

 

[amirm]

Bruno had encouraged me to run intermodulation test with 19 and 20 kHz tones. Alas, I forgot in my haste to post this review. So here it is:

I matched levels with Benchmark AHB2. I was surprised to see so much lower intermodulation distortion with 1ET400A. The first pair of sidebands is more than 10 dB cleaner and the rest almost don't exist! Well done. I let Bruno explain why this is so.

 

[amirm]

True.
Would be interesting if you measure only 1 channel of this 1ET400A amp turned on. If it can beat the single nc400 then.

Here you go:

Note that the lower distortion advantage of Purifi 1ET400A gets lost in the above below max power since noise dominates THD+N.

EDIT2: Original measurement was made with an almost broken cable. I fixed that together with making sure only one channel was driven (two were in original graph). High-gain was also enabled.

 

[amirm]

Also interesting to see what the maximum power output would be if each 1ET400A were driven by a single SMPS1200

I am glad you asked me this as running in stereo showed that the previous comparison I made was the good channel of Hypex NC400 against the "bad" channel in 1ET400A.

Here is the stereo measurement using identical power supply in both:

I refined the graph a bit showing a bit more power now for the 1ET400A. That aside, as noted on the graph, I wonder if the 1ET400A amps are more efficient resulting in higher output power from the same supply.

EDIT: Original graph was with a faulty cable. Fixed version above.

 

[boXem]

I am not sure what bandwidth JA uses at stereophile. Mine is at 1 Mhz but there is an AES-17 filter in addition:
View attachment 28894
Let me know what you learn.

That the Q of the second order low pass behavior is not far away from 0.7?

 

[tktran303]

This is amazing that's we're getting to an era of utter sonic transparency and affordability in amps that don't weigh 100lbs or need jewellery for casework.

@Bruno Putzeys :looking forward to seeing what you will accomplish with with loudspeaker drive units.

regards,
Thanh from Australia.

 

[audioBliss]

but if you look at this result you got when you only measured one channel of that nc400-implementation with a shared SMPS, nc400 has even lower distortion, right? So nc400 monoblocks might be "the shit"?

The nc400 monoblocks are the shit basically. Even if the Eigentakt would have a slightly better measurements for one channel it's running the SMPS 1200 already. In any case the DIY Eigentakt will for sure be way more expensive than the nc400 and 6 months away it seems.

 

[audioBliss]

I am glad you asked me this as running in stereo showed that the previous comparison I made was the good channel of Hypex NC400 against the "bad" channel in 1ET400A.

Here is the stereo measurement using identical power supply in both:

View attachment 28902

I refined the graph a bit showing a bit more power now for the 1ET400A. That aside, as noted on the graph, I wonder if the 1ET400A amps are more efficient resulting in higher output power from the same supply.

Why show without the pre-gain? Will anyone ever be running this with 12.8dB gain?

 

[phoenixdogfan]

Here you go:

View attachment 28899

Note that the lower distortion advantage of Purifi 1ET400A gets lost in the above below max power since noise dominates THD+N.

Have to wonder if the noise is coming mainly from the HYPEX SMPS 1200, and if Bruno is planning to offer an improved Purifi switching PS.