More technical details about nuPro

[Goran]

Hello everybody!

*Some of the questions which will be asked here are strictly technical, so please bear with me
It may be that some support from Nubert technical team will be mandatory!
*Sorry for my English, I do not speak German and I am using Google translate

A am planning to buy an active speaker system with digital inputs.
So far, nuPro series is among my personal favorites because of its completeness in inputs and great reviews throughout the internet.
I have several questions about the playback from PC and general technology of the nuPros.

1.PC Playback from USB

As I understand, the nuPro is handling digital signals up to the final stage, when PCM signal is converted to PWM in the amp.

-Can I use ASIO driver on my PC/Mediaplayer for bit-perfect playback?
-What maximum bit depth and sample rate can be accepted via USB? Is it 24 bit/96 KHz or some other?
-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)?
-Is the USB interface adaptive or asynchronous (i.e. is the PC or nuPro in control of the clock)?
-Is the USB input galvanic isolated from PC (battery playback vs AC current playback)?

2.Playback from analog input
-In what format is the analog input digitized? Is it 16/44.1, 16/48, 24/88.2 or 24/96?

3.DSP details
-What is the resolution of the DSP architecture? Is it 16, 24, 32 or 35 bits?
-Is the volume control fully digital - 16/24/32/35 bits?
-Is DSP resmpling all inputs to a common 24/96 or are the inputs treated natively?
-Is the crossover DSP based, and how steep is it - 6, 12, 18 or 24 dB per octave?

4.Amplifier details
-What is the SNR at full power AND at 1W?
-What is the frequency of the PWM clock?
-Is the digital amplifier open loop or with feedback loop? If later, how is feedback loop exactly implemented?
-Can you show some graphs about the THD+N, linearity (how many bits it can resolve), jitter etc?

Maybe most of my questions are answered in some kind White Paper for the nuPro series, so if it exists, please point me toward it!!!

With best regards,
Goran

[R. Steidle]

Hello Goran,

thank you for your interest in our products. Since the lead developer for our nuPro series is currently on holiday and your questions are rather detailed, I'd like to ask you for a few days' patience until his return. We will probably still not be able to answer all of your questions since a lot of them concern technical details of the DSP architecture, which have not been made available publicly by the chip's manufacturer.

Best regards,

R. Steidle

[Goran]

Hello Mr.Steidle,

Thank you for the reply!

I will be patient and eagerly await the answers.

Sorry for too much and too technical questions asked, but as I am going to replace my 20-year old system and I want to do it only once and properly, I obviously catch typical audiophile neurosis called upgraditis . Also, actives and DSP are completely new field to me, and as a technically educated person I want to know as much as possible about the way they function.

I am considering to buy a pair of nuPro A-200 before Christmas, and as far as I can see, there is almost NOTHING equivalent on the marketplace (only KEF X300A and Quad 9AS - which are technically inferior to A-200, and Dali Kubik Free + Xtra and Dynaudio XEO 4, which are way too expensive).

Regarding DSP and Amp questions, I am not asking for any trade secrets, only for some commercial info which is already available at other manufacturers (in order to compare), for example http://www.thewelltemperedcomputer.com/ ... -paper.pdf.

Thanks once again and have a nice day!!!

With best regards,
Goran

[homer0815]

Hi there.
First of all, I do not own the NuPro yet, but I'm eager to buy the 300 when I get my income tax back.
I read a lot about the new NuPro and so I will try to help you.

ASIO is supported, even in the old versions A10 & A20.
I used the ASIO-Plugin in foobar2000 with my current NuPro A10.

According to the handbook the maximum input samplingrates are
USB: 16Bit/48kHz
Optical: 24Bit/96kHz
Electrical: 24Bit/96kHz

As far as I know the DSP works internaly with 24/96kHz and does upsampling wherever needed.
So all input signals and analog inputs are converted to this samplingrate.
According to fairaudio.de a Cirrus Logic CS5364 is used as ADC.
http://www.cirrus.com/en/pubs/proDatash ... 364_F5.pdf

[Goran]

Thanks for the very useful info, homer0815!

Analog input:
As I can see from the useful link you provided for ADC Cirrus Logic CS5364, the chip works in 24 bit resolution, and with sample rates of 48, 96, and 192 kHz, so native sample rate of 44.1 kHz is not supported and the DSP probably upsamples to its internal resolution (24/96 as you say, although I couldn't find any info at Nubert or on internet).

Digital USB input:
Yeah, I also found it is 'only' 16/48. Although I can live comfortably without hi-res capability of USB input, I am concerned about handling 44.1 sample rate, and again I can not find anywhere if DSP is upsampling to 24/96 or not.
This is of paramount interest to me, since if the DSP is not handling 44.1 natively and up to the PWM stage of the amplifier, than audible artifacts will be introduced when upsampling from 44.1 to 48 or 96 kHz (oversampling to 88.2 or 176 kHz would be different story and definitely acceptable).
Also, if the DSP is upsampling, then it is pointless to use ASIO driver for bit-perfect 16/44.1 playback, since it may be that Windows is better place to convert 44.1 to 48 kHz then DSP in nuPro (it will convert 16/44.1 to 32 bit float and dihter the signal to 16/48).

Digital SPDIF:
Although I do not want to additionally buy USB/SPDIF converter for the PC, it would be useful to know if these inputs can handle 16/44.1 without upsampling.

RELEVANT INFO FROM NUBERT TECHNICAL STUFF WOULD BE HIGHLY APPRECIATED!!!

By the way homer0815, how are you satisfied with NuPro A10? How big is your listening room and does A 10 have enough sound pressure and bass weight? My room is not big at 18 m2 (5 x 3.5 m), so I hope nuPro A-200 fill suffice.

With best rgds,
Goran

[taco]

Dear Goran,

what I can say: A-200 will do fine on 18 m².
Sorry I can´t help with your other questions....

[homer0815]

My office is about 20m², but it is in the attic with a roof slope.
It is also used as a guest room and with the (sleeping)couch inside and the carpet on the floor, there is a lot of damping.
I want to buy the A300 because I want a deep bass without the need of a subwoofer.
In my living room I have a NuBox 681/411/311 setup with 2 SVS PB12-NSD - thats enough for me

Right now I'm using the NuPro A10 with Windows 7/Foobar2000/ASIO or Arch Linux/DeadBeef/ALSA and all my music is ripped in flac -8 16bit 44,1kHz.
I really don't care about digital upsampling as long as it works for me. I'm only using ASIO because I don't want Windows or DirectX to mess up with the sound.

[Goran]

Thank you for the replies!!!

I found that the DSP is 32-bit (which is good for low-loss volume control) and that it is resampling everything to 24/96.

However, this is information from online reviews.

Nobody from Nubert team has jumped into this thread to clarify posted questions and dilemmas.

With best regards,
Goran

[Sencer]

By the way homer0815, how are you satisfied with NuPro A10? How big is your listening room and does A 10 have enough sound pressure and bass weight? My room is not big at 18 m2 (5 x 3.5 m), so I hope nuPro A-200 fill suffice.

Hi Goran,

I think it depends entirely on your expectations. I have a single A-20 in our bedroom (19,5qm) and I am time and time again amazed at how deep and clear a sound it produces - for it's size. I find it to be at least as filling as small pianocraft sets (certainly I would rate the A-20 above in every quality), but then again I am not sure I would compare it with larger (even compact) speakers in terms of "filling". Maybe my view is abit distorted due to it only being mono.

Regards
Sencer

[taco]

Nobody from Nubert team has jumped into this thread to clarify posted questions and dilemmas.

well...but....

Since the lead developer for our nuPro series is currently on holiday and your questions are rather detailed, I'd like to ask you for a few days' patience until his return.

and still....

[...]concern technical details of the DSP architecture, which have not been made available publicly by the chip's manufacturer.

Nubert staff is highly motivated and very helpful, however - and that could have been a google translator problem, or it´s just my limited english - I found your 1st post a little demanding. (no offense...just saying.... )