NAD C 389 residual noise and first experience

[dedobot]

Hi,
I purchased a NAD C 389, MDC2 BluOS-D Modul and DiracLive full bandwidth license a few weeks ago. It should replace my current setup WiiM Pro->MinDSP DDR-24 (DiracLive)->Yamaha R-N803D. On the one hand I like der C 389 a lot, but I found it's residual noise rather disappointing, especially since I used high sensitivity Speakers (Lowther Fidelio with DX-3, rated ~ 96dB 2.83V/1m). It has a clearly audible hiss even at 3.3m listening distance. The Yamaha R-N803D (70uV residual noise) and also my vintage Yamaha A-590 (35uV (CD Direct) / 90uV (Pure Direct) residual noise) from 1996 have a practically inaudible residual noise/hiss in my setup.
Since I cannot find any residual noise numbers for the NAD C 389 I decided to measure it. I do not have access to uV precision measurement gear so I just performed a simple acoustic near field measurement (12.5cm away from the Lowther Fidelio) of all amplifiers and without any amplifier at all (to get a baseline of the general environmental noise to compare with). The result is:

View attachment 422343
We can clearly see the C 389 has a significantly higher noise floor above 1 khz than any of the Yamaha amplifiers in any mode.

I found some residual noise measurement on similar NAD amplifiers:
https://www.soundstagenetwork.com/i...ts&catid=97:amplifier-measurements&Itemid=154 (2 NCORE Hypex)
Noise level (A-weighted) <55uVrms <55uVrms
Noise level (unweighted) <82uVrms <79uVrms

https://www.soundstagenetwork.com/i...ts&catid=97:amplifier-measurements&Itemid=154 (1 Ucd Hypex)
Noise level (with signal, A-weighted) <130uVrms <132uVrms
Noise level (with signal, 20Hz to 20kHz) <166uVrms <167uVrms
Noise level (no signal, A-weighted) <102uVrms <97uVrms
Noise level (no signal, 20Hz to 20kHz) <130uVrms <124uVrms

https://www.soundstagenetwork.com/i...ac&catid=97:amplifier-measurements&Itemid=154 (1 NCORE Hypex)
Noise level (A-weighted) <190uVrms <180uVrms
Noise level (unweighted) <310uVrms <280uVrms

So only the C 399 seems to perform well here, I am wondering what the C 379 and C 389 would measure ( I guess similar to C 3050).

Most reviewers describe the NAD amplifiers as very silent:

only

and
https://hometheaterhifi.com/reviews/amplifier/integrated-amplifiers/nad-c-399-hybrid-digital-dac-amplifier-review/ "The first thing I noticed is the noise floor – as in, there isn’t one. This is the quietest integrated amp I’ve yet heard. Even the superb M28 multi-channel amp I reviewed a while back had an audible noise floor. Previous Hypex-based NAD products I’ve reviewed also had audible noise when no signal was present. The C 399 has somehow eliminated this."

notice a potential residual noise issue.

Maybe only the C 399 has a low residual noise suitable for high sensitivity speakers in the NAD product line. Any good or bad experience with C 379, C 389, C 399, C 3050, M10 V2/3 and high sensitivity speakers? I would really like to see residual noise data in any amplifier measurement.

Beside the residual noise issue I mostly like the C 389, minor issues I found

1. Pseudo 2 speaker pair terminals, you cannot use it to compare or just even switch between 2 loudspeaker pairs. In the last 45 year I have never seen such a strange feature, basically just a Bi-wiring helper. The Yamaha R-N803D in contrast allows seamless switching between 2 speaker pairs and is able to activate the corresponding YPAO calibration and level adjustment while switching, which is great to compare speakers.
2. The remote control operates a little bit like controlling 2 different devices (Amp and MDC modul) in one box by having to switch between both via “AMP” and “BLS” buttons, so e.g. switching from TV to Internet radio input is somewhat complicated.
3. After power up BluOS is not able to play where is had previously stopped. So if you want to continue listening to the same internet radio station as you did before shutting down the device you have to select the station again.

Currently I am not sure if I will keep the C 389 or resell it.

Best regards
Randolf

I had old NAD C370 paired with Focal Aria 948. Sources was CD player, Fiio portable player , laptop. Deadly quiet on all inputs. Focals Aria are sensitive speakers.

 

[pogo]

The UMIK-1 is less suitable for such measurements, as you can see here: Link

 

[Randolf]

The UMIK-1 is less suitable for such measurements, as you can see here: Link

I fully agree:

"The microphone is well suited for level measurements in the 50-105dB range. It is not suitable for measurements in quiet areas. You can clearly see USB interference (1kHz and harmonics) in the spectrum (see picture in the gallery). These interferences lead to the well-known "chirping". For room acoustic measurements, however, this is irrelevant."

So I am already lucky to be able to measure the delta between the amps with the UMIK-1, otherwise I would just had to say Yamaha is quiet and NAD has an audible hiss.

Meanwhile I got feedback from NAD, they suggest the device being faulty and I should return it for service. I will probably give it a try.

I just noticed another very minor issue. You can rename the inputs in the NAD menu. I renamed all used inputs and disabled the unused ones. For the "HDMI eARC” I set "TV". works fine, but if I disconnect the device from the power cord and reconnect it after some time it comes back as "TDMI eARC” and I have to set it again. For the other inputs it just works fine, bizarre! Hoping a future firmware update may fix that.

 

[Randolf]

The C 389 is send to service, NAD service and local dealer were very helpful so far.

While waiting for the return and outcome I did some math (hopefully correctly) just for fun to estimate, if residual noise becomes audible or not in a setup, it might generally be useful for those running high sensitivity speakers and/or near field listening.

Some amplifier specs and measurements already provide the residual noise (Voltage output with no input / volume turned down completely), it might be A-weighted or not. I think one can also use the idle noise from Amirm's power on/of output measurement. Otherwise one can estimate it from a low output (5W, 1W or even lower) SNR measurement, which is also often found. I think you can also use Amirm's power versus distortion measurement by looking at 20-100 mWatt range. Calculation goes like this:

Estimate residual noise voltage (Ures) in micro Volt from a measured SNR (SN) at certain output power (P) and impedance (R):
Ures in uV = (10^6 * SQRT(P*R)) / 10^(SN/20)

e.g.:
SN=90db
P=5W
R=8Ohm
=> Ures = (10^6 * SQRT(5*8)) / 10^(90/20) = 89 uV

or estimate residual noise voltage (Ures) in micro Volt from a measured SNR (SN) at certain output voltage (U):
Ures in uV = (10^6 * U) / 10^(SN/20)

e.g.:
SN=90db
U=2.83V
=> Ures = (10^6 * 1.83) / 10^(90/20) = 89 uV


Together with the speaker sensitivity spec or measurement we can calculate the noise floor at listening position. Unfortunately speaker sensitivity specs are sometimes not accurate / comparable and in room sensitivity can be higher:

Anyway here we go:

Calculate resulting noise (SPL) at distance (D) in meters for given residual noise (Ures) in micro Volt and Speaker sensitivity (S) (measured at Voltage (U) at 1m).
SPL = S + 20 * log((Ures / 10^6) / U / D)

e.g.:
Ures= 89 uV
S=96db
U=2.83V
D=3m
=> SPL = 96 + 20 * log((89 / 10^6)/2.83/3) = -3.6dB

or calculate resulting noise (SPL) at distance (D) in meter for given residual noise (Ures) in micro Volt and Speaker sensitivity (S) (measured at P Watts at 1m) and speaker impedance being R.
SPL = S + 20 * log((Ures / 10^6) / SQRT(R*P) / D)

e.g.:
Ures= 89 uV
S=96db
P=1W
R=8Ohm
D=3m

=> SPL = 96 + 20 * log((89 / 10^6) / SQRT(8*1) / 3) = -3.6db

Now we need to check if the SPL noise floor is above human hearing threshold (Fletcher–Munson or iso-226-2003 curve) which goes down to -2 / -9 db in the most sensitive frequency range. So my number example is probably almost inaudible.

 

[Randolf]

NAD has replaced my device with a new C389, unfortunately I got no measurement protocol from the service. The difference in serial number is just 270, so both devices might been manufactured at a similar time. Anyway the issue is exactly the same, audible hiss and my amateur measurement comes to the same result (it is really 100% reproducible, eventually slightly different microphone position or ambient noise do not make a difference). I contacted the NAD support again, waiting for feedback now. To me it currently looks like the C389 is not meeting its spec and is just on par with C379, C3050, M10, C700 specs or perhaps a whole set of manufactured C389 devices is faulty.

 

[Randolf]

I just noticed that NAD spec on website and manual for the C 389 differ significantly:

https://nadelectronics.com/product/c-389-hybrid-digital-dac-amplifier/:

https://nadelectronics.com/wp-content/uploads/2022/05/C389-OM-EN-v14.pdf:

So we have a significant difference 85db vs. 95db for speaker out and 98db vs. 107db for headphone out. The manual spec matches well with my measurement and listening experience, the website spec not. For now I am running the C 389 as streaming preamp with Dirac Live and the Yamaha R-N803D as power amp, which works pretty well.

My conclusion so far is, if you have a similar setup with high sensitivity speakers and listening distance and you are sensitive to residual noise hiss stay away from NAD C3050, M 10, C 700, C 379, C 389 instead you may consider the C 399 (which hopefully fulfills its specs, at least website and manual spec are in sync and soundstage measurement looks good).

 

[Randolf]

Unfortunately the replacement C 389 has a faulty headphone amplifier and I had to return that one as well. Meanwhile DALI GmbH (NAD Sales in germany) has replied (translated from german by google translate):

"I'm sorry to hear that the replacement device isn't working properly either.
Unfortunately, the fact that the technical data is incorrect or differs can happen due to an error in translating or updating the device properties and will be corrected accordingly by us on the website.
As NAD sales, we have no influence on the return policies of our specialist dealers if the end customer wishes to return a device purchased there for any reason.
That's why we unfortunately have no control over the purchase contract that was concluded between you and the dealer."

So neither my dealer nor NAD sales seem to see a problem with incorrect manufacturer specs and point to each other when it comes to return a device, so I just have to live with the mediocre noise floor. At least they promised to correct the website spec. In germany we have a 2 weeks return without reasoning law for online purchase, unfortunately I was a little too late. I strongly suggest to check each and every feature of an NAD product as soon as it arrives and return it immediately if you detect any kind of problem instead of trusting into any goodwill from NAD or dealer.

Once I have a fully functional C 389, you eventually may find mine with MDC2 BluOS-D Modul and Dirac Live full bandwidth license for a reasonable price on ebay kleinanzeigen in germany .

 

[Old_School_Brad]

Unfortunately the replacement C 389 has a faulty headphone amplifier and I had to return that one as well. Meanwhile DALI GmbH (NAD Sales in germany) has replied (translated from german by google translate):

"I'm sorry to hear that the replacement device isn't working properly either.
Unfortunately, the fact that the technical data is incorrect or differs can happen due to an error in translating or updating the device properties and will be corrected accordingly by us on the website.
As NAD sales, we have no influence on the return policies of our specialist dealers if the end customer wishes to return a device purchased there for any reason.
That's why we unfortunately have no control over the purchase contract that was concluded between you and the dealer."

So neither my dealer nor NAD sales seem to see a problem with incorrect manufacturer specs and point to each other when it comes to return a device, so I just have to live with the mediocre noise floor. At least they promised to correct the website spec. In germany we have a 2 weeks return without reasoning law for online purchase, unfortunately I was a little too late. I strongly suggest to check each and every feature of an NAD product as soon as it arrives and return it immediately if you detect any kind of problem instead of trusting into any goodwill from NAD or dealer.

Once I have a fully functional C 389, you eventually may find mine with MDC2 BluOS-D Modul and Dirac Live full bandwidth license for a reasonable price on ebay kleinanzeigen in germany .

Never put your trust in such entities. No matter the promises or written contracts, there's always a disclaimer to void everything -or at the very least, they'll stall until most people give up.

 

[Randolf]

Still waiting for my repaired C389. Since NAD has not yet corrected the specs, i have looked up soundstage measurements and NAD web and manual specs. There are quite a lot minor and major inconsistencies between NAD Web and NAD Manual specs in various modells as well as major differences between SoundStage measurement and NAD spec of the C3050. I would only expect low inaudible residual noise when used with high sensitivity speakers from C399, C298 and M33 (marked green). I have marked the NAD specs red which look very suspicious to me.

	C3050	C399	C700	M10V2	C298	C379	C389	C700V2	M10V3	M33	M10
SoundStage! Lab: Noise level (with signal, A-weighted)	<130uVrms	<55uVrms	<240uVrms	<180uVrms	<33uVrms
SoundStage! Lab: SNR (A-weighted, ref. 1W out in 8 ohms, 500mV input)	88dB	94.6dB	82dB	85.2dB	98dB
NAD web (A-weighted, ref. 1W out in 8 ohms, 500mV input	>95dB	>95dB	>84dB	>85.1dB	>98dB	>85dB	>95dB	>84dB	>85.1dB	>98dB	>85dB
NAD manual (A-weighted, ref. 1W out in 8 ohms, 500mV input)	>95dB	>95dB	>84dB	>85.1dB	>98dB	>85dB	>85dB	>87dB	>82dB	>98dB	>90dB

 

[valerianf]

@Randolf , I think it is time to go back to class AB amplifiers.
This is the solution against hiss.
Do not believe in the specifications issued from the marketing department.