Review and Measurements of Purifi 1ET400A Amplifier

[Qrun]

Hello everybody,

I'm new on this forum, following the discussion which is quite technical, you might be of some help, eventhough it's partly related to this thread of discussion.
I moved to a new home and also inheritate of a pair of JBL L300 summit and recuperate a good turntable with a huge collection of LP, so I decided to update my HiFi setup.

I have three sources : the turntable with a radial J33 phono amp, a CD player (Marantz CD67SE) and a computer.

The backbone of the installation will be a RME ADI-2 Pro FS used as a pre-amp/volume control/DAC, collecting the signal :
- from the PC on the USB
- from the turntable on the XLR analog input
- from the CD player through SPDIF optical

My question is related to the amp that will be a AUDIOPHONICS HPA-S400ET based on the Purifi module.
As far as understood their is an interface card (installed by AUDIOPHONICS) providing a selectable input gain that can be bypass.

So my first question is that if I set up the ADI-2-PRO-FS to provide +24dBu @0dBFS on the Analog output, I should be in the range of output voltage perfect to bypass the interface card from Audiophonics, am I right?

Second question, Do you have any idea of the good selection of input gain on the analog input of the RME to fit with the XLR ouput of the phone amp (spec Balanced outputs 600Ω, -60dB mic-level)? +24 dBu, +19 dBu, +13 dBu, +4 dBu @ 0 dBFS ?
It's not always clear with all those differents units.

You might say, just test... but I would prefer avoid blowing my speaker with a setup with to high gain...

Thanks in advance for your answers.

 

[phoenixdogfan]

Is there a DIY chassis (or plate for ghent audio case) made specifically for this?

No Ghent case right now. He keeps promising one but has not delivered as yet. I had already bought the 300mm wide Ghent case for a NC 400 build, and I am finding there are three options here.

(1) Go to a custom metalwork shop and have them drill holes for the Purifi Eval and fabricate a new back for the Ghent case.

(2) Order an existing Ghent case, get the holes drilled for the Purifi module and wire up a connection to the Ghent case by using disasssembled XLR cable and BFA bannana Z plugs to keep the existing connection on both the Purifi and the Ghent case.

(3) Remove the connections on the Purifi module and wire it up to either the Ghent case or something else like the Ghent directly.

Each has its plusses and minuses. The topic is developed in depth on the Purifi Diy build thread.

 

[maty]

A curiosity: I have not found YouTube videos with audio demos using the Purifi 1ET400A, something striking after the elapsed time.

https://www.youtube.com/results?search_query=purifi+1et400a

Maybe on other platforms. In any case, it would be appreciated if some user upload one, using a good microphone and not those of mobile phones. Or only the audio files.

 

[Stretchneck]

A curiosity: I have not found YouTube videos with audio demos using the Purifi 1ET400A, something striking after the elapsed time.

https://www.youtube.com/results?search_query=purifi+1et400a

Maybe on other platforms. In any case, it would be appreciated if some user upload one, using a good microphone and not those of mobile phones. Or only the audio files.

I'm also supprised by this

 

[VintageFlanker]

A curiosity: I have not found YouTube videos with audio demos using the Purifi 1ET400A, something striking after the elapsed time.

https://www.youtube.com/results?search_query=purifi+1et400a

Maybe on other platforms. In any case, it would be appreciated if some user upload one, using a good microphone and not those of mobile phones. Or only the audio files.

Why you would need that?

I've never understood people who are listening to gears... through YouTube. What you are listening is a recording, compressed for YT codecs... And then, you listen to it with your DAC/Amp/Speakers and room (or headphones). How that could give any idea about "how it sounds"? This makes no sense to me.

 

[maty]

Something off topic

Despite the compression of YouTube, if the recording is done well it can be useful. An example of this is Ron Brenay. Two good microphones pointed in the near field to each box. Very impressive the bass of the two open subwoofer.

• YouTube X-LS Review | Sound Clips with Commentary

Yesterday I saw a good video about another class D, BOSC - 150W HiFi Monoblock GaN Audio Amplifier; the explanations and demos at the end of the video were very useful to me to discard it definitively.

• YouTube GaN? A class D amp that is different. Orchard Audio Power amp review.

 

[Stretchneck]

I believe it does give you a decent idea of what differences might be present, namely tonal quality. Obviously many of the traits will be missing, sound stage, detail retrival etc... but it helps.

 

[mocenigo]

Something off topic

Despite the compression of YouTube, if the recording is done well it can be useful. An example of this is Ron Brenay. Two good microphones pointed in the near field to each box. Very impressive the bass of the two open subwoofer.

• YouTube X-LS Review | Sound Clips with Commentary

Yesterday I saw a good video about another class D, BOSC - 150W HiFi Monoblock GaN Audio Amplifier; the explanations and demos at the end of the video were very useful to me to discard it definitively.

• YouTube GaN? A class D amp that is different. Orchard Audio Power amp review.

Such videos are useless. How can you judge the quality of the amplifiers with them? Maybe the folks that purchased EVAL1 kits are reasonable persone and see no point in wasting time and bandwidth in such a thing.

 

[PaulD]

I believe it does give you a decent idea of what differences might be present, namely tonal quality. Obviously many of the traits will be missing, sound stage, detail retrival etc... but it helps.

Not at all.

As VintageFlanker explained:
It will mostly give someone an idea of the sound of the room and the resonances, modes and reflections, the recording is made in.
It will secondly be coloured by the response of the microphone (next worse things than speakers).
Then it will be coloured and resolution removed by the codecs putting the audio through an MP3-like process for transmission.

There is no way to determine any device's sound quality from that. People who claim it are kidding themselves. Getting the equipment in your own home/work, or at least in your actual presence, is the only way to tell.

 

[maty]

More off topic

The problem, in addition to YouTube audio compression, is that many do not properly configure the operating system to squeeze the most out of the audio. And, among other things, make the sound be processed by a good soft audio player like JRiver MC 64 bits thanks to the WDM driver (there other options to other players) -> Kernel Streaming.

• https://wiki.jriver.com/index.php/WDM_Driver

I notice a lot of difference between the default audio browser settings and mine configuration, even when Win10 is fully optimized for multimedia in the two cases.

PS: it is not MP3. AAC https://en.wikipedia.org/wiki/Advanced_Audio_Coding

 

[VintageFlanker]

More off topic

The problem, in addition to YouTube audio compression, is that many do not properly configure the operating system to squeeze the most out of the audio. And, among other things, make the sound be processed by a good soft audio player like JRiver MC 64 bits thanks to the WDM driver (there other options to other players) -> Kernel Streaming.

• https://wiki.jriver.com/index.php/WDM_Driver

I notice a lot of difference between the default audio browser settings and mine configuration, even when Win10 is fully optimized for multimedia in the two cases.

PS: it is not MP3. AAC https://en.wikipedia.org/wiki/Advanced_Audio_Coding

@maty, YouTube compression is the least of troubles there. There're more important issues:

It will mostly give someone an idea of the sound of the room and the resonances, modes and reflections, the recording is made in.
It will secondly be coloured by the response of the microphone (next worse things than speakers).

 

[Michael YYZ]

-20 dB vs. - 75 dB! Why the difference?

 

[Vincentponcet]

-20 dB vs. - 75 dB! Why the difference?View attachment 72987View attachment 72988

An AES17 filter has an attenuation of >60db above the indicated frequency, ie 40KHz.
It was used for nc400 but not for 1et400a
If you add -60db to the 1et400a test, they would look more similar.

 

[Michael YYZ]

Thank you! Does this mean that in in real life the output low-pass filter in a Class D amplifier module would still pass -20 dB of HF content? How would this impact the behaviour of the speakers / tweeters? Any major impact on them?

An AES17 filter has an attenuation of >60db above the indicated frequency, ie 40KHz.
It was used for nc400 but not for 1et400a
If you add -60db to the 1et400a test, they would look more similar.

 

[Shadders]

Hi,
I have the latest Hifi News August 2020 which has a review of the Nad M33 streaming/DAC amplifier which uses the Purifi modules.

I have seen a presentation (which cannot be downloaded) indicating that for class D, the AP equipment requires signal conditioning and the 22.5kHz low pass filter.

I understand that the Hifi News QC suite has a bandwidth of 100kHz, and as such the THD figures in the magazine are based on a measurement bandwidth of 100kHz,.

Is it possible to extrapolate the AP results or use a higher bandwidth low pass filter to see what the THD is at 20kHz (Hifi News indicates 20kHz 1watts into 8ohms, THD=0.003%).

Does the purifi module modulate the class D PWM signal to push the switching artefacts further up the spectrum and hence a 100kHz measurement bandwidth will indeed result in a 20kHz, 1W into 8ohms, THD=0.003% ???

Thanks and regards,
Shadders.

 

[VintageFlanker]

I have the latest Hifi News August 2020 which has a review of the Nad M33 streaming/DAC amplifier which uses the Purifi modules.

Here is the Lab Report from HFN:

Seems to perform worse than ET400s with Evaluation Board... Still, I would prefer to wait for the M33 properly measured by @amirm in all regards: Amp, DAC, streamer, room correction etc.

 

[digitalfrost]

But why. The M22/M27 was so good.

 

[Shadders]

Here is the Lab Report from HFN:


Seems to perform worse than ET400s with Evaluation Board... Still, I would prefer to wait for the M33 properly measured by @amirm in all regards: Amp, DAC, streamer, room correction etc.

Hi,
I have seen some Infineon designs etc., and their 80kHz measurement bandwidth of an amplifier at 20kHz, 1watt into 8ohms, has a THD much higher than the HFN results. In examining the Purifi literature, the THD=0.0007%, but i expect that this is with the 22.5kHz measurement bandwidth.

So the HFN QC test suite shows that even with 100kHz measurement bandwidth, the THD is very low at 20kHz. This is quite a technical feat for such a low THD with class D (only 3x the 22.5kHz measurement bandwidth result).

Regards,
Shadders.

 

[Vincentponcet]

Here is the Lab Report from HFN:


Seems to perform worse than ET400s with Evaluation Board... Still, I would prefer to wait for the M33 properly measured by @amirm in all regards: Amp, DAC, streamer, room correction etc.

They say analog input pass through ADC. And it is not an amp, but an integrated amp, so in this case ADC-potentially some processing-DAC-preamp-amp(purifi). There is a Dirac Live into it too, they don't say if they fully disabled it or not.
So the numbers could not be the same as just the purifi amp.
They show that using digital input gives a much higher SNR, in about 110db, so more in the range of what is expected than the low 94db of analog input.

Hence this test is not really useful.

 

[sdo_riga]

I'd appreciate any guidance on the following scenario. I consider an upgrade from NAD 804 to either Revel F228Be or Revel F226Be. Revel lists 50-350W as the recommended amplifier power range for F228BE and 50-200W for F226BE. Both speakers have 90dB sensitivity. I want to start with a stereo amp based on1ET400A and have an option for bi-amp down the road. Is Purifi 1ET400A a good selection power output wise for each of the speakers? For F228Be 1ET400A output falls under the max of 350W. For B226Be 1ET400A is above the 200W.