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Forum List => Technical Support => Topic started by: corboid on August 11, 2010, 08:52:36 am

Title: NAD PP3 via USB - Loud noise in Win7 but not in XP
Post by: corboid on August 11, 2010, 08:52:36 am
Hi,
I have similar problems as it has been discussed earlier, but I have a feeling there is no solution yet.

I can make pure digital noise free recordings via USB using my laptop Lenovo T60p running Win XP, but when I use my mini PC HP 210-1023 running Win7 I get an awful hiss making the recording totally useless. I means that my PP3 should NOT be deffective but the problem is connected to Win7 and/or VinylStudio. The noise is somewhere 20-40 dB below the normal classical music levels. If I wash it out digitally it affects the music too much.

Listening to the characteristics of the noise it gets me to belive that windows7 makes the sound analogue and then digitalises it or adds some analogue noise to the digital signal from USB (Yes, I checked that nothing more than USB/NAD PP3 is selected for recording)
Even if PP3 does not have any level control I can access the recording level in Win7 (but not in XP!) and the noise is scaled with the level.

I use USB-headset so I should get pure digital path NAD PP3 >> Win7 + VS >> file >> USB-headet. But it sounds very "analogish".
My mini-PC has only  a single analog sound socket (4-pin combined in/out) so the by pass AlpineSoft uses to propose by recording the analog signal is not applicable. Anyhow I purchased the NAD to get the signal digitally and not mess with poor A/D-converters inside the PC. ;)

I hope you have a solution for this problem.
Best regards,
Corboid

(PS: I used the "set gain to 1" setting in VS level control, for win7)
Title: Re: NAD PP3 via USB - Loud noise in Win7 but not in XP
Post by: Paul Sanders (AlpineSoft) on August 11, 2010, 12:17:07 pm
Can you send me a sound sample please?  Please record about 1 minute to MP3 format (to keep the file size down) and send it to:

p DOT sanders AT alpiinesoft DOT co DOT uk

Thanks.

You might also like to try a different USB cable and / or port.  I'm sure this problem is hardware related.  If the PP-3 didn't work with Windows 7 (or with VinylStudio on Windows 7) we would certainly know about it and I have tested this combination explicitly.  Also, ensure that the phono connections are tight and that the turntable is earthed to the lug on the PP-3.

Setting the digital gain to 1 is the right thing to do.  Any other setting cases Windows 7 to scale the digitised signal and that will result in clipping or loss of dynamic range, depending which side of the line you are on.  The lack of a recording slider in XP is a blessing, not a curse.

I think the analog route is closed off because, according to the specifications for your machine, your socket is for a Microphone and hence mono only.
Title: Re: NAD PP3 via USB - Loud noise in Win7 but not in XP
Post by: corboid on August 11, 2010, 12:42:15 pm
Hi Paul,
sure, I'll send you samples from win7 and xp tonight.

First I expected the problem to be some electric interference so I tried three different USB-cables with and w/o ferrit cores.
I also tried to isolate the PP3 from the computer by a powered hub w/o any difference. Same result when running the PC on batteries or 230V/AC.
Title: Re: NAD PP3 via USB - Loud noise in Win7 but not in XP
Post by: Paul Sanders (AlpineSoft) on August 11, 2010, 12:54:15 pm
OK, thanks.  It's very odd, I must admit.  Anyway, I'll take a listen and see what I make of it.
Title: Re: NAD PP3 via USB - Loud noise in Win7 but not in XP
Post by: corboid on August 12, 2010, 09:29:29 am
A follow-up note for other people looking for a solution:

I discovered that the USB-socket on the left side of the HP mini-PC produces much higher noise that the two USB's on the right side.
And both sockets have higher noise levels than I get on my Lenovo.

Paul Sanders believes that my PP3 (purchased in september 2008) can be the problem and needs to be replaced.
Title: Re: NAD PP3 via USB - Loud noise in Win7 but not in XP
Post by: Paul Sanders (AlpineSoft) on August 12, 2010, 01:22:29 pm
*Possibly* needs to be replaced.  I need to follow this up with NAD.
Title: Re: NAD PP3 via USB - Loud noise in Win7 but not in XP
Post by: mgd on August 15, 2010, 06:21:17 pm
I just want to add my 5 cents.

I purchased a NAD PP3 which was very noisy both on PCs and on my Mac. The noise was not clear white noise but rather typical computer noise with clearly audible tonal components around 1000Hz. A friend told me that the USB clock is 1ms so the 1Khz noise is most probably USB clock noise that reached the ADC in the NAD PP3.

After a bit discussion, Hifi klubben replaced my NAD PP3 as they told me this was a known problem for units with a serial number below or at H88PP3G02501.

My new unit is much better, BUT there is still clearly audible noise which is about 15dB louder than the noise from my Macs built-in sound card (using analog in). Also the noise is still not white noise but contains audible tonal components (peaks) around 4kHz and 17.5kHz (to high pitched to be heard by many) as well as a lot of harmonics.

My Mac's built-in sound card has only white noise (no peaks at any frequencies) at a very low level.

I am going to return my NAD PP3 and I cannot recommend this unit.

If I am going to digitize my old vinyl records and spend a lot of hours doing it, I want to be sure the recordings is not masked in audible noise. (And remember, we are not talking white noise hiss, but annoying computer noise.)

Instead, I would recommend finding a decent RIAA preamp (maybe NAD PP2) and use another external sound card (or maybe your built-in sound card if it is without noticeable noise).

/Martin

P.S.

quote author=corboid link=topic=183.msg547#msg547 date=1281601769]
I discovered that the USB-socket on the left side of the HP mini-PC produces much higher noise that the two USB's on the right side.
And both sockets have higher noise levels than I get on my Lenovo.
[/quote]

I believe the main problem is that the PP3 picks up the USB noise which it shouldn't. Different PCs and Macs have different levels of noise from the USB ports. That could explain the differences you experience. In any case, this noise shouldn't reach the ADC in the PP3.
Title: Re: NAD PP3 via USB - Loud noise in Win7 but not in XP
Post by: Paul Sanders (AlpineSoft) on August 15, 2010, 06:27:57 pm
I'm, sorry to hear that.  The problem does seem to be dependent on the PC as well as the PP-3 - most people are OK.

In corboid's case (after some off-line discussion and talking to NAD), he can get acceptable recordings from all but one particular USB port on one particular PC, which demonstrates that the PC is injecting the noise in his particular case.  He tells me he will be getting a new PC soon so it will be interesting to hear how that pans out.  We have scotched the theory that it was anything to do with Windows 7 per-se.
Title: Re: NAD PP3 via USB - Loud noise in Win7 but not in XP
Post by: mgd on August 15, 2010, 09:26:01 pm
In corboid's case (after some off-line discussion and talking to NAD), he can get acceptable recordings from all but one particular USB port on one particular PC, which demonstrates that the PC is injecting the noise in his particular case.

As far as I understand (from what I have been told), USB will always be more or less noise (transmission of clock signal, multiplexing of packages sent/received) and the USB device must be able to handle this. In case of a USB connected A/D converter it must be able to suppress the noise from the USB port.

So you are right that in corboid's case one of his PCs is injecting more noise than the other into the PP3, but the PP3 ought to be able to handle that.

If you have a look at the attached file: The red graph is a spectrum analysis of the signal I record from the PP3 when the line-in signal to the PP3 is silent (a stopped Logitech Squeezebox). The green graph shows the result of recording exactly the same signal (silence) at the same level using my Mac's built-in sound card (analog line-in).

As you can see, the noise introduced by the PP3 is around 13dB higher, but more important it has a lot of audible peaks. Especially, the one just below 4kHz is annoying. This is my second PP3. The first one was much worse (you have heard it yourself as I send the recording to you earlier this summer.

Regards,
Martin
Title: Re: NAD PP3 via USB - Loud noise in Win7 but not in XP
Post by: Paul Sanders (AlpineSoft) on August 16, 2010, 12:09:06 pm
I do feel a certain conflict of interest here but NAD use a TI PCM2904 converter chip which includes the A/D converter stage and it is this chip which is fed from the power supply in the PC.  The 2904 is widely used in the industry for other devices in the PP-3's price range and I suspect that these will also suffer from the same problem when the PC power supply is noisy, e.g.

http://forum.audacityteam.org/viewtopic.php?f=27&t=33018&start=0

(the ART uses the same chip).

None of which helps you of course if you are afflicted by this problem.

Thanks for posting the sound plots.  They make interesting viewing. 
Title: Re: NAD PP3 via USB - Loud noise in Win7 but not in XP
Post by: corboid on August 17, 2010, 12:15:02 pm
Hi,
I still did not have time to analyse if the noise is sent to the PP3 via the VCC/5V-connector (pin 1), ground (pin 4) or via the data connectors (pin 2/3). Need to get an oscilloscope first.

A well designed A/D should assure having a clean supply voltage and not let the ripple march into the analog signal and fool the A/D conversion.

I have some ideas to isolate the PP3 from the computer. Unfortunately the ready made opto-isolators for USB are many times more expensive than the PP3 (and can only handle USB1.1 and USB2.0/low speed, ie up to a little more than 1 MBaud), so it needs some hands-on experiments.

It seems NAD are good on analogue design but they have a lot to learn about digital design. PP3 is excellent as an analogue amp. But the digital signal is just "fair" but not as good as it should/could.

//Corboid
Title: Re: NAD PP3 via USB - Loud noise in Win7 but not in XP
Post by: Paul Sanders (AlpineSoft) on August 17, 2010, 02:21:35 pm
Yes, I know the USB chip gets its power from the PC but I'm not sure whether it's a requirement that it does so.  Anyway, I will be interested in the results of your findings.  It's possible that the noise pickup happens in the phono stage, rather than in the A/D convertor itself, of course, and attaching a scope lead is bound to affect the results you get...
Title: Re: NAD PP3 via USB - Loud noise in Win7 but not in XP
Post by: corboid on August 18, 2010, 08:47:13 am
No, the analogue phono signal is totally unaffected, I would hear it via my amp (I have only high-end equipment all the way so I would hear it immediately).
I.e. the ripple is caught in the digital part of the PP3 and not in the phono-amp.

I contacted my NAD reseller, they were well aware about the problem and promised to replace my box (S/N H7ZPP3Gxxxxx ==> manufactured december 2007!).
I will see how much better it will be before I make further improvements (if needed).
Title: Re: NAD PP3 via USB - Loud noise in Win7 but not in XP
Post by: Paul Sanders (AlpineSoft) on August 18, 2010, 12:23:39 pm
That's interesting.  We had another case where the customer _did_ hear it via his amp.  I guess it's a more complex problem than at first appears.

Anyway, good luck.  Noise levels are definitely lower on the later models - NAD redesigned the PCB layout in the light of what they learned from the first model.
Title: Re: NAD PP3 via USB - Loud noise in Win7 but not in XP
Post by: corboid on August 19, 2010, 10:07:18 am
I found an interesting gadget providing a clean USB power voltage
http://www.aqvox.de/usb-power_en.html

If it works as it claims it could be a solution for computer noise picked up by the external A/D-converters:s.
I'm a bit worried that they only inject a clean VCC, and let the data signal pass through. If the disturbance sneak in that way, it will not help.

However the product costs a bit, EUR 87.00.
Title: Re: NAD PP3 via USB - Loud noise in Win7 but not in XP
Post by: Paul Sanders (AlpineSoft) on August 19, 2010, 01:18:33 pm
OK, thanks.  Seems like a lot of money for such a simple thing.

I'm, not sure why NAD elected to bus-power their USB chip.  Seems to me it could be powered from the PP-3's own power supply.  Next time I talk to them, I will ask.
Title: Re: NAD PP3 via USB - Loud noise in Win7 but not in XP
Post by: corboid on August 19, 2010, 01:49:11 pm
Isolating analogue and digital stages is normally a very GOOD idea because it minimizes risk for getting the digital noise into the analogue path.

The problem is that USB allows very unclean voltage because is meant for powering digital computer peripherals.  Using such a voltage quality to power ADC is a BAD idea.
Thus they should do some cleansing of the voltage - capacitors and voltage regulators etc, *or* use an own power supply of known quality (like Aqvox does).

Title: Re: NAD PP3 via USB - Loud noise in Win7 but not in XP
Post by: corboid on August 19, 2010, 06:33:27 pm
I just fetched the replacement unit. This time it has S/N H9XPP3Gxxxx, ie made 2009/October.

And now to the anti-climax.
The noise is still there, and the news is that when USB is connected to the HP mini-PC the noise also gets to the amp+speaker. This as I know I did not get earlier with my previous box (S/N H7ZPP3Gxxxx (2007/december)).

Luckily I cannot hear the noise via amp+speakers when connecting to Lenovo - it comes just a few seconds when the USB-cable is plugged in and then it becomes silent.

So to sum up - the PP3-design is still not suitable for use with computers.
To fail to fix a "known problem" is not really a trade mark of a master. I did not expect this from NAD and their QA. Apparently someone forgot to test the product on a range of computers.

So it's time to go for the plan B and replace  PC's voltage feed to the PP3 by few parallel connected  4.5V batteries (4.5V is almost within the allowed voltage range for USB) and if it works, use a stabilized and low-pass filtered power supply. A DIY-version of Aqvox unit. Must get an oscilloscope to take a look at the signals.
Title: Re: NAD PP3 via USB - Loud noise in Win7 but not in XP
Post by: Paul Sanders (AlpineSoft) on August 19, 2010, 07:13:28 pm
OK, good luck.  I'm a bit disappointed, I have to say, although I think your case is a bit unusual.  There are many thousand happy PP-3 owners out there.

4 x NiMh = 5V, more or less.  It probably doesn't matter if you creep a fraction over.  Anyway, please keep me posted.  I don't have a scope either, otherwise I would take a look myself, but my PP-3 is a pre-production unit so I might not learn much anyway.
Title: Re: NAD PP3 via USB - Loud noise in Win7 but not in XP
Post by: corboid on August 22, 2010, 11:25:59 am
I just soldered a experiment board with USB-sockets so I can manipulate the USB/VCC-voltage to PP3.

The first test was to add some capacitors between VCC and GRD (pin 1 and 4) - I don't want to overload USB so I used modest 100nF parallel with 470pF hoping to suppress some of the disturbance frequencies. But it did not help. Now I try to replace the PC's USB-voltage by injecting some other stable 5V voltage.


Another finding - I also compared with my Behringer UCA200 ADC/DAC that only supports the line level signals (I use it for interfacing an audio-mixer to computer over USB).
And this is SILENT, as expected even with my noisiest USB-socket, when I connected UCA200 to the PP3's output.
On the other side when PP3 is switched to line level the noise level is 40-50dB lower (over USB).
Maybe it's not the ripple in the USB voltage feed to the ADC is the main problem (as I assumed)?

I.e. apparently NAD screwed up seriously the phono-level when interfacing the ADC... Doh!...
Title: Re: NAD PP3 via USB - Loud noise in Win7 but not in XP
Post by: Paul Sanders (AlpineSoft) on August 22, 2010, 11:41:29 am
Thanks for the update.  I think the problem is that the high sensitivity needed for a phono input (just a few mV) makes it particularly sensitive to noise pickup.  I shall be interested to hear how the PP-3 performs with a clean USB power source.
Title: Re: NAD PP3 via USB - Loud noise in Win7 but not in XP
Post by: corboid on August 28, 2010, 03:13:29 pm
Bad news.
I made a setup where I replaced the USB-VCC/5V voltage coming from the computer by a VERY clean voltage from an AC/DC-unit and unfortunately  the noise is still there on quite same level and spectrum.
I used a 5V power supply specified for medical usage - Mascot 9619/5V. It has low ripple < 30 mV p-p and switching freq of 40kHz.

My setup was:

[Computer-USB]----<standard USB A/B cable>--- [injection device with fresh 5V]---<standard USB A/B cable>---[PP3]
Nothing is earthed, and I run my PC (HP mini-PC 210-1023) on battery.

I do not like that the 1st cable still contains the dirty voltage that can contaminate the other three USB wires, but I do not think that it is the main problem.
(It seems all the USB-wires are already contaminated when leaving the PC - unfortunately difficult to prove w/o an oscilloscope).
Anyhow I will make a custom cable that cuts of computer's VCC at the socket and injects the fresh 5V at the PP3-socket. But I have low believe in this.

I also tried to regenerate the digital signals D+/D- by passing a hub (powered by the Mascot device). This makes similar or same noise.

Apparently the NAD PP3 is designed in such a way that the USB-signals are received in such a way that they are are radiated internally inside the PP3-box to the sensitive MM/MC-phono stage. The latter has sensitivity of 5mV(MM) or 380 uV(MC). When 16-bit resolution is used it means the phono stage needs to receive radiation of  just 76 uV (or 5,7 nV) to be affected by a single digital level.

My conclusion: This means that PP3 requires that the connected computer MUST provide an excellent internal USB-voltage generation without ripple on any of the USB-wires.
Thus PP3 works satisfactory with the expensive Lenovo T60p but not with the cheap HP mini PC. I will soon get a Lenovo T510 and I am excited to see which noise I'll get. The risk is that newer PC's use more and more the solutions integrated into the main chip-sets and will be equally "crappy" when used for analogue sound ;)

The solution I advice is the one I described earlier:
- do not connect USB-cable to PP3 unless you have noise-free USB-signals (i.e. use PP3 as a PP2, or don't buy PP3 - buy PP2!)
- use another USB A/D-converter to convert line level signals from PP2/PP3 (or your amp's monitor/preamp-out signal) to USB-signals



Title: Re: NAD PP3 via USB - Loud noise in Win7 but not in XP
Post by: Paul Sanders (AlpineSoft) on August 28, 2010, 06:48:43 pm
OK, thanks for the update.  As you say, a bit disappointing.

It's not completely clear to me whether the noise pickup comes from the PC power supply (which contains various switched-mode components of course) or the USB signal themselves, but the fact that it varies from one PC to another seems to imply that it is the former rather than the latter.  It did occur to me that noise might arise from crosstalk within the USB cable.  The obvious solution there is to inject your clean supply at the PC end of the cable rather than at the PP-3 end, or, as you say, cut the power supply cable at the PC end.

Once your investigations are complete I will send a link to this thread to NAD to see if they would like to comment.
Title: Re: NAD PP3 via USB - Loud noise in Win7 but not in XP
Post by: corboid on August 30, 2010, 11:50:35 am
A home made USB does not help (as I feared). The pull-down resistors between D+/D- and Vcc and Ground leak the PC noise to PP3 over D+/D-.

The best solution would be if NAD provided an isolator (or better, built it into the PP3).  It would make PP3 a real usable audio device and not just a half heartily designed device.
Some hint's how it should be done for real:
http://www.ecnmag.com/Articles/2010/03/Simplify-USB-Isolation-in-Medical-Applications/
http://pdfserv.maxim-ic.com/en/an/AN3891.pdf
http://hackaday.com/2009/09/18/usb-isolation/

We are talking about quite a low component cost by < EUR 10 in production volumes i.e. would make a "super-PP3" only 5-10% more expensive if addressed during design.

Title: Re: NAD PP3 via USB - Loud noise in Win7 but not in XP
Post by: Paul Sanders (AlpineSoft) on August 30, 2010, 08:28:10 pm
OK, I will make NAD aware of this thread.  Thanks very much for your efforts.

One thing though: any phono preamp using the USB chip that the PP-3 uses (which is most of them) is likely to have the same problems.  I'm sure NAD have the shortest possible connections between that chip and the USB socket, and have kept them as far away from the phono stage as they can.
Title: Re: NAD PP3 via USB - Loud noise in Win7 but not in XP
Post by: corboid on August 31, 2010, 08:51:18 am
I found another link that addresses power noise propagation (EMI) and design issues/advices for USB from Intel:
http://www.ti.com/sc/docs/apps/msp/intrface/usb/emitest.pdf

(but they do not discuss that USB stage might act as an antenna sending noise and disturbing the low level phono statges)
Title: Re: NAD PP3 via USB - Loud noise in Win7 but not in XP
Post by: Paul Sanders (AlpineSoft) on August 31, 2010, 11:24:39 am
OK, thanks.  I'll pass that along too.
Title: Re: NAD PP3 via USB - Loud noise in Win7 but not in XP
Post by: oilburner on November 17, 2010, 01:36:11 pm
after bouncing a few ideas off Paul I have come to the following conclusions.

To cut a long story short:

the PP3 has always got a very quiet whine when the USB input is active. This is most noticeable on the MM input because this has the most gain.

If I disconnect my cartridge (though leaving it connected doesn't actually make any difference) and connect the arm to the PP3 I get the whine at unacceptable levels.

If I disconnect the earth lead from the pick up arm and earth the arm via the screen on the audio cable instead, the noise goes away.

The conclusion is that the 9 inches of unscreened wire within the arm is causing the problem. Whether this is because it is acting as an aerial or because there is some interaction between the mains earth on the tube and the wires I don't know. All I can say definitively is that changing the earthing stops the noise.

So, unless I have an old batch PP3 (apparently they did a redesign at some point to stop a noise issue?), or a faulty unit, the suspicion is that everyone who has a 'correctly' earthed turntable will get this problem.

Michael.
Title: Re: NAD PP3 via USB - Loud noise in Win7 but not in XP
Post by: Paul Sanders (AlpineSoft) on November 17, 2010, 02:05:40 pm
Thanks very much for this.  I will give NAD another prod.