NAD M33 Streaming Amplifier Review

[Thalassophile]

I use an acoustic track female singer with no bass at very low volume subwoofer 80
hz .tone controls off to replicate the issue

Good to know. That seems to match PDXAudio's experiences as well. I think I will make a mix of contrasting tracks. If there are any specific ones you would recommend, let me know and I will add them.

 

[Kaboo]

I just thought I would see how this amp would perform with different music.I found this distortion on the first 2 acoustic albums I tried.Now acoustic is ruined for me
This was one of them .Dua Lips. live acoustic EP. Third track at 19 sec. HD track from Amazon music

 

[pogo]

Second replay from NAD support: (Clipping bug confirmed by NAD engineers. Bug limited to only those who use subwoofer and never run Dirac live or use Dirac filters with too levels too high).

There is a reproducible cracking sound (artifacts) at some music points. In my example at lower frequencies (see my post #494) with DL and higher levels.
I don't use the subwoofer function. My subwoofer is passive and is connected like a low frequency speaker part in bi-wiring (see also post #407).

There are still some gain factors to be reconsidered in the design

 

[Kaboo]

There is a reproducible cracking sound (artifacts) at some music points. In my example at lower frequencies (see my post #494) with DL and higher levels.
I don't use the subwoofer function. My subwoofer is passive and is connected like a low frequency speaker part in bi-wiring (see also post #407).

There are still some gain factors to be reconsidered in the design

Yes this has been going on with the m33 for a long time .Also with other nad units for over a year and a half.same issues .class action. No one is screwing me

 

[Thalassophile]

Curious what they mean by those who never run Dirac. I did a number of different tests yesterday and could not hear any distortion on all four of the tracks mentioned in this thread, with Dirac off and the subwoofer on at various cross-overs. (I did mange to piss off my downstairs neighbor though when one subwoofer test went off the rails ). So once you do a Dirac sweep, does it permanently adjust the levels in your system in some way (including the maximum volume) until you do another calibration? In other words, is Dirac ever truly "off" once integrated into your system. Is that why some people notice this bug and others don't?

 

[wgb113]

I’ve started looking at The M33 as a nicer all-in-one alternate to the C658/C298 combo since those are both having issues only to discover users are having issues with it as well...

Now I’m starting to lean towards more basic units. I tried Dirac Live before via miniDSP and was not thrilled with the results and it sounds like it may be still operating poorly on the M33.

 

[pogo]

M33 users, please double check:
After the new BluOs update to version 3.14.5 tonight, my Dirac filters don't seem to sound so lifeless and cloudy (NAD Target Curve). I have not performed a new filter export!
Can any of you notice any improvement after the update?
I'll have a closer look over the next few days.

 

[Reed]

M33 users, please double check:
After the new BluOs update to version 3.14.5 tonight, my Dirac filters don't seem to sound so lifeless and cloudy (NAD Target Curve). I have not performed a new filter export!
Can any of you notice any improvement after the update?
I'll have a closer look over the next few days.

Using a C658, I did the update. No change right off the bat. Opened my Mac to see if there were any changes to the Dirac app. I have two saved sessions. I switched sessions and I had the same experience you did. Switched to the other session, same story as you. I have three saved curves that all sound different (as they should). However they all sound different from, say, last week or pre update. Vivid is the description I’d use. There is more in the high end but it’s much more than that. Everything is more defined top to bottom. Channel separation is much better. I stumbled into this, as you did, so it’s not the placebo effect.

 

[EB1000]

Agreed. My room is small and the subwoofer rarely "kicks in," but I am going to leave it engaged for the next week and just have background music on all day. I use a stand desk while WFH that is between the two tweeters, so I can hear every detail. Will report back.

Let me be clear, all NAD processors (C658, T778, M33) have the distortion issue when any processing such as Dirac or bass management is activated. This is a hardware limitation due to lack of processing headroom. Tone control and using replaygain on can limit the distortion but will also limit the output level and scarify dynamic range. NAD cannot and WILL NOT fix this. This is the final replay I got after escalating the issue to their management:

-----------------------------
Hi Eli

Thanks for the sample. We have been investigating this matter for some time now. The inter-sample clipping (Rhye distortion) you are hearing is created at the time of recording on some "hot" tracks and cannot be resolved in any other way than reducing the gain on the track.

Please make adjustments accordingly. Sorry.

--------------------------

There is no FW fix! This is what happens when digital processing is carried out using the original bit depth of the recording, you can easily run out of headroom. I've had it with NAD. I've ordered the MiniDSP SHD, which will be connected to dual Hypex NC400.

See other similar discussions about NAD distortion here:

https://www.audiosciencereview.com/...st-this-for-me-female-vocal-distortion.22151/

 

[Kaboo]

Let me be clear, all NAD processors (C658, T778, M33) have the distortion issue when any processing such as Dirac or bass management is activated. This is a hardware limitation due to lack of processing headroom. Tone control and using replaygain on can limit the distortion but will also limit the output level and scarify dynamic range. NAD cannot and WILL NOT fix this. This is the final replay I got after escalating the issue to their management:

-----------------------------
Hi Eli

Thanks for the sample. We have been investigating this matter for some time now. The inter-sample clipping (Rhye distortion) you are hearing is created at the time of recording on some "hot" tracks and cannot be resolved in any other way than reducing the gain on the track.

Please make adjustments accordingly. Sorry.

--------------------------

There is no FW fix! This is what happens when digital processing is carried out using the original bit depth of the recording, you can easily run out of headroom. I've had it with NAD. I've ordered the MiniDSP SHD, which will be connected to dual Hypex NC400.

See other similar discussions about NAD distortion here:

https://www.audiosciencereview.com/...st-this-for-me-female-vocal-distortion.22151/

Well what would ones next step be I'm pissed that they have sold me this broken amp .I only had a 14 day return window. Others should be aware of this farce.

 

[Thalassophile]

Let me be clear, all NAD processors (C658, T778, M33) have the distortion issue when any processing such as Dirac or bass management is activated. This is a hardware limitation due to lack of processing headroom. Tone control and using replaygain on can limit the distortion but will also limit the output level and scarify dynamic range. NAD cannot and WILL NOT fix this. This is the final replay I got after escalating the issue to their management:

-----------------------------
Hi Eli

Thanks for the sample. We have been investigating this matter for some time now. The inter-sample clipping (Rhye distortion) you are hearing is created at the time of recording on some "hot" tracks and cannot be resolved in any other way than reducing the gain on the track.

Please make adjustments accordingly. Sorry.

--------------------------

There is no FW fix! This is what happens when digital processing is carried out using the original bit depth of the recording, you can easily run out of headroom. I've had it with NAD. I've ordered the MiniDSP SHD, which will be connected to dual Hypex NC400.

See other similar discussions about NAD distortion here:

https://www.audiosciencereview.com/...st-this-for-me-female-vocal-distortion.22151/

OK. I was only replying to a few posters who claimed that the distortion they heard only happened when a subwoofer was activated, and said I would see if the same thing happened on my end under those circumstances. That is all.

To date, I have not experienced any of the issues mentioned in this thread, and could not replicate them on the tracks that were mentioned, whether streaming BluOS, using optical in, using the line in, whether or not Dirac was engaged, whether or not subwoofer was "on" or "off", all in every combination of these variables.

Will read through your thread.

 

[fcracer]

Let me be clear, all NAD processors (C658, T778, M33) have the distortion issue when any processing such as Dirac or bass management is activated. This is a hardware limitation due to lack of processing headroom. Tone control and using replaygain on can limit the distortion but will also limit the output level and scarify dynamic range. NAD cannot and WILL NOT fix this. This is the final replay I got after escalating the issue to their management:

-----------------------------
Hi Eli

Thanks for the sample. We have been investigating this matter for some time now. The inter-sample clipping (Rhye distortion) you are hearing is created at the time of recording on some "hot" tracks and cannot be resolved in any other way than reducing the gain on the track.

Please make adjustments accordingly. Sorry.

--------------------------

There is no FW fix! This is what happens when digital processing is carried out using the original bit depth of the recording, you can easily run out of headroom. I've had it with NAD. I've ordered the MiniDSP SHD, which will be connected to dual Hypex NC400.

See other similar discussions about NAD distortion here:

https://www.audiosciencereview.com/...st-this-for-me-female-vocal-distortion.22151/

I’m a bit lost here. If the distortion is due to the recording clipping (“too hot” in the words of the NAD tech), how can you expect firmware to fix a recording issue?

 

[EB1000]

I’m a bit lost here. If the distortion is due to the recording clipping (“too hot” in the words of the NAD tech), how can you expect firmware to fix a recording issue?

They didn't say it can be fixed. They said we must reduce the gain somehow. But if the recording is the blame then gain wont change a thing. They made a design mistake which they can't fix...

 

[Mnyb]

Reduce the gain in your playback software like -3dB and test if you have a computer source that can do this or if its some app then activate replay gain just to try then you know.

 

[pogo]

Using a C658, I did the update. No change right off the bat. Opened my Mac to see if there were any changes to the Dirac app. I have two saved sessions. I switched sessions and I had the same experience you did. Switched to the other session, same story as you. I have three saved curves that all sound different (as they should). However they all sound different from, say, last week or pre update. Vivid is the description I’d use. There is more in the high end but it’s much more than that. Everything is more defined top to bottom. Channel separation is much better. I stumbled into this, as you did, so it’s not the placebo effect.

Which speakers do you use?

 

[fcracer]

M33 users, please double check:
After the new BluOs update to version 3.14.5 tonight, my Dirac filters don't seem to sound so lifeless and cloudy (NAD Target Curve). I have not performed a new filter export!
Can any of you notice any improvement after the update?
I'll have a closer look over the next few days.

I think it's a placebo effect. Since this is ASR, we need to test things. Here are four measurements taken with REW with BluOS 3.14.3 vs. 3.14.5. One set of measurements are with Dirac Live off, and one set is with Dirac Live on using the Harman 8db curve.

As can be seen, with Dirac Live off, there is absolutely no difference between the different firmware versions. Subjectively, I also notice no difference.

With Dirac Live on, using the Harman 8db curve, we can once again see absolutely no difference in the measurements. This was also the same for impulse response, distortion and any other measures that REW offers.

I also ran the same tests using the NAD curve and got the exact same results. There is no difference, so any reduction in the music being "cloudy" or "lifeless" is more likely due to the owner's mood rather than any change resulting from the new BluOS version.

Hope the above helps for folks that are thinking of doing the update, but were concerned based on the comments posted here about it changing the sound; you have nothing to worry about.

 

[fcracer]

They didn't say it can be fixed. They said we must reduce the gain somehow. But if the recording is the blame then gain wont change a thing. They made a design mistake which they can't fix...

Following the link that a member posted with the Lana Del Ray "For Free" song, at 1:10, there is a phrase, "Waiting for the walking greeeeeeeeeen". During that phrase, if I turn the subwoofer filter on, I do hear the distortion. With the subwoofer filter off however, there is no distortion. Furthermore, if I turn on the tone controls, which reduce the gain of the amplifier (to give some headroom), the distortion goes away.

To summarize:
Dirac On, Subwoofer Filter Off, Tone Controls Off: No distortion
Dirac On, Subwoofer Filter On, Tone Controls Off: Distortion
Dirac On, Subwoofer Filter On, Tone Controls On: No distortion

Therefore, for people who listen to music that is recorded at clipping levels and need to use a subwoofer, you can try to turn the tone controls on (leave them at 0db) and test if the distortion also disappears for you.

 

[pogo]

I think it's a placebo effect. Since this is ASR, we need to test things.

Correct, but with your measurement you did not measure the swing-in or swing-out behavior of a complex signal! An additional time-axis would be important to make a change visible. 'Steady test signals' like a sweep that only show the maximum amplitude of a frequency do not help here.
Which measurement microphone did you use?
Which speakers do you use?

 

[GianDi]

the analog input is digitized first and then converted back to analog for amplification

why??????

 

[fcracer]

Correct, but with your measurement you did not measure the swing-in or swing-out behavior of a complex signal! An additional time-axis would be important to make a change visible. 'Steady test signals' like a sweep that only show the maximum amplitude of a frequency do not help here.
Which measurement microphone did you use?
Which speakers do you use?

REW using umik-1 and Monitor Audio Silver 6 speakers. I can also share spectral delay plots that include the time domain, but again, the plots between the two firmware versions are the same. Happy to conduct more tests if you'd help me understand how to quantify and test "cloudy", "swing-in" and "swing-out". I think the key here is, if you're happier with the new firmware, then that's great!