More technical details about nuPro

[R. Steidle]

Hello Goran,

we finally have some answers for you. Sorry it took us so long to respond but with our developer being on holiday and then me being sick, collecting all the data took longer than expected. Also in part due to your questions and similar ones we received from other customers we will be expanding the technical data given for the nuPro series at some point in the future. Now let's get right to your questions (for easier reading I've marked them bold):

-Can I use ASIO driver on my PC/Mediaplayer for bit-perfect playback?
Yes, you should be able to do that.

-What maximum bit depth and sample rate can be accepted via USB? Is it 24 bit/96 KHz or some other?
For the USB interface, it's 16/48.

-How does nuPro handling the USB input? If I send, for example, 16/44.1 or 24/88.2 or 24/96 signal, does the DSP handle it natively or is doing sample rate conversion or upsampling/oversampling (and if yes, to what format)?
The conversion is actually done by the computer prior to sending it to the USB audio device. Any signals sent will always be in 16/48 format.

-Is the USB interface adaptive or asynchronous (i.e. is the PC or nuPro in control of the clock)?
Asynchronous.

-Is the USB input galvanic isolated from PC (battery playback vs AC current playback)?
It's not galvanically isolated.

-In what format is the analog input digitized? Is it 16/44.1, 16/48, 24/88.2 or 24/96?
Analog input signals are digitized in 24/192 format by the ADC.

-What is the resolution of the DSP architecture? Is it 16, 24, 32 or 35 bits?
32 bits floating.

-Is the volume control fully digital - 16/24/32/35 bits?
Fully digital at 32 bits.

-Is DSP resmpling all inputs to a common 24/96 or are the inputs treated natively?
Analog input is converted as stated above, all digital signals entered via S/PDIF are treated natively, if possible.

-Is the crossover DSP based, and how steep is it - 6, 12, 18 or 24 dB per octave?
It is DSP based with complex quality, a minimum of 24 dB per octave.

-What is the SNR at full power AND at 1W?
116 dB a-weighting at full power and 114 dB a-weighting at 1W.

-What is the frequency of the PWM clock?
384 kHz.

-Is the digital amplifier open loop or with feedback loop? If later, how is feedback loop exactly implemented?
Overall feedback loop.

-Can you show some graphs about the THD+N, linearity (how many bits it can resolve), jitter etc?
THD+N is 0.02 % (electronically), 0.8 % (overall, acoustically). Most graphs we have regarding this data are for internal use only, sorry.

Thank you again for your interest in our products.

Best regards

R. Steidle

[Goran]

Hello Mr.Steidle,

Thank you for the comprehensive information you provided regarding some technical aspects of the nuPro series.

Obviously, the great reviews nuPro's are receiving are objectively backed up by great technology implemented: top-notch 32 bit floating DSP architecture, 4-th order crossover (24 dB/octave), 32 bit digital volume control, and most of all completely digital treatment of the signals until the final stage of converting them to Pulse Width Modulated signal.

Results, as from the info you provided, exceeds the price of the nuPros: SNR of 114 dB/1W and 116 dB/full power implies real-world resolution of around 19-19.5 bits, which is up there with the best digital amplifiers costing many times more.

Regarding THD+N measured only 0.8% 'overall, acoustically', please clarify at what point this is measured, since if it is at standard 1 m from the speaker, this implies that these results are really excellent (having in mind that good passive speakers can distort from 1-3% up to 10%).

My only confusion is whether I rightly understand the treatment of the input signals, so please comment if I am right in the following assumptions:

Music from PC through USB:

-FLAC files 16/44.1 shall be converted by Windows to 16/48, since nuPro will accept only 48 kHz and not 44.1 kHz native.

-NuPro will convert 16/48 signal to 24/96 in order to be handled by DSP (the rest of the path is clear).

-This in my mind contradicts with the claim that I can use ASIO driver for bit-perfect playback, since ASIO is 16/44.1 (the same as my FLAC files). Please clarify!

-Since nuPro has a strait digital path and converts digital signal directly to PWM amplified signal, we can not talk about classic DAC and asynchronous USB interface because to my (limited) understanding there is no clock in nuPro, or am I wrong?

Music from analog source:

-Analog signals will be digitized to 24/192 by the ADC, and then down converted to 24/96 to be handled by DSP.

I will very much appreciate these final clarifications from Nubert team, as I am preparing to become happy owner of nuPro A-100 comes end of December!!!

With best regards,
Goran

[Virtualizer]

Hi Goran,

an ASIO driver is not directly available but you can use Kernel Streaming to bypass Windows Mixer with the nuPro USB DAC implementation.
Another alternative would be to use the 3rd Party ASIO4all driver if you have to use ASIO e.g. because some other Software does rely on ASIO.
If you only want to playback Music then Kernel Streaming should be as good as ASIO.
For the Samplerates I just connected my nuPro to verify it and the nuPro USB DAC does support 32KHz, 44.1KHz and 48KHz natively.
So there should be no problem from this perspective.

Best

[Goran]

Hi Virtualizer,

Thanks for the useful info!

I have read a lot about drivers and I will try ASIO (if available), kernel streaming, WASAPI, ASIO4all (with Foobar 2000) - they all should sound identical on a revealing system like nuPro, so we shall see when I upgrade (my current system is very old).

I want to connect my TV with optical in and my Arcam miniBlink (for streaming aptx bluetooth from my smartphone) with analog in, but the most importance I give to the USB music playback from my Win7 PC - that's why I ask so many questions related to this area.

If, as you confirm, nuPro supports 44.1 kHz natively (contrary to the answer I received from Nubert), this will be of most significant importance to me!!

Also, I need to know if the USB interface is really asynchronous (for the maximum suppression of jitter). If you have the time and will to help me, there are some simple programs that can confirm or deny this:
http://www.thewelltemperedcomputer.com/ ... ptorDumper
http://www.head-fi.org/t/546092/confirm ... med-or-not

Otherwise, I am already >50% inclined to buy nuPro. Are you satisfied with the sound?

Best regards,
Goran

[Virtualizer]

Hi,

50% is not very much until now..
With such high expectations there is a slight possiblity that there could be a disappointment afterwards
That does not mean that I'm in any form not satisfied with my pair of A-300.
After nearly one year of use I'm still amazed how they sound in my room.
If you place them open in the room I would tend to go with the A-200 at min. not the A-100.

The USB interface is asynchronous, just checked that with the Thesycon Tool. Thanks for the links btw, didn't know of them.
For me it would be no real criteria, though. From my perspective you get very decent sound with the internal USB DAC, that is the most important thing.

Best

[Goran]

Thank you very much for your help and assistance, Virtualizer!

A-100 was a typing mistake. I intend to buy A-200, which I think will be sufficient for my 20 m2 room (if not, there will always be an option to add nuPro sub at a later date).

By the way, my other options are Dali Kubik Free + Xtra which are more in the A-100 league but with A-300 price; KEF X300A which have limited connections; QUAD 9AS which are too small (100 mm mid/bass driver); and Dynaudio Xeo 4 which are too expensive.

I will buy the speakers in the second half of December, and for now nuPro A-200 are my first favorites.

My only gripe is that I will not be able to play hi-res music through USB but hey, I can live with that!!!

Thanks once again

[Goran]

In addition to my last set of questions and in order to complete my understanding of the technical details about nuPro, my last question is:

What kind of digital filter is used in nuPro series: is it Linear Phase Sharp roll-off, Linear Phase Slow roll-off or Minimal Phase filter?

Best rgds,
Goran