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NAD M33 Streaming Amplifier Review

Pragmatic

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Hello all, first post.

I've owned the M33 for a year now and I've experienced similar issues with the gain, I've tried to solve the issue with the support but after a lot of email exchange we did not find a root cause for the problem.

My observations is also that with Dirac and tone control enabled at the same time the loss of master gain is the most significant I've ever experienced with an integrated amplifier. I own a Marantz SR6013 which I've used with Audyssey and an Icepower 1200 and never experienced such a gain reduction while using the different features.

I've also experienced that after some Dirac calibration there is additional gain loss depending of how much Dirac corrects the original speaker measurement and changing the dirac correction filter to follow the original improves slightly the available power on the master gain. Unfortunately turning Dirac off doesn't seem to restore the gain to factory settings, nor performing a simple factory reset in my case. I usually have to perform a full firmware installation via USB to get back to an acceptable master volume level.
Using Dirac seems to trigger the gain issues in my case and I always end up reverting to factory settings. I don't really need Dirac since I've a dedicated room optimised for music but I do appreciate the additional control provided by Dirac on Bass.

I mostly use Tidal (connect) as my source and I've been trying to understand how Tidal loudness normalization works in combination with Bluos track and Album gain in order to find out if some settings combination can add another handicap to the master gain. I've found this interesting article but I don't know yet if this is affecting gain management on the M33.

I'm still very happy with the M33, the sound quality is the best I've experienced so far, It's a beautiful integrated amp. I was glad that I could use the balance control with Dirac after going crazy trying to achieve a centered image in my setup (always to the left). The recent fix of the tone controls finally makes it usable (without Dirac). It's just annoying that the software can have such a negative impact on the sound in some cases. Gain management is still a mistery to me, it's normally loud on POP, but on classical music or songs with high dynamic range I also end up turning the volume to -15db and with Dirac enabled this doesn't leave a lot of margin for a close to realistic listening experience.
Hi. If you see post #1050 and #1052, would be very neat if you could also run the same dB test, along with posting your speaker sensitivity and distance from the speakers etc.

Well, the guy from the HiFi shop suggested that it may be due to both the volume wheel being more linear than usual, combined with the fact that the amp has very low distortion (so loud listening doesn't trigger that earache you get from cheaper amps). I don't know - max volume has been enough so far, even with Dirac on, but for very dynamic pieces, like classical, it's only just enough. With my old NAD C375BEE, I had the volume wheel at max 40% when listening to classical music (with peaks well over 100dBa). About the same volume as 80% (where 90% is max with Dirac) on the M33. Though, I never tried cranking the wheel all the way, since it's less powerful than the speakers and would blow some expensive nautilus tweeters. For other music genres, I usually stop at between 65-75%, since the loudness war has killed just about all dynamics in modern music.

In your case, with Dirac and tone controls enabled, the loss should be around -17dB in theory - that's definitely a whole lot.

Overall I am happy with the sound too, except when listening to rock and metal. The snare drums sounded magical on the C375BEE, for some reason. No doubt it colored the sound somehow, to my liking.
 

Pragmatic

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I set a lower limit at -60dB, that's why I got 67% at -20dB.
Now I fooled myself once and will never activate the % display again:facepalm:
Oh snap, glad we solved that one. Thanks for checking, haha. I was really wondering about that one.
 

pogo

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Well, the guy from the HiFi shop suggested that it may be due to both the volume wheel being more linear than usual, combined with the fact that the amp has very low distortion (so loud listening doesn't trigger that earache you get from cheaper amps).
Here is a translated excerpt from a German forum:

I am professionally settled in the PA area and CarHifi, so I first set with "pink noise" all amplifiers with the same level so that I had a comparison to listen without volume differences. Here I clearly noticed that the M33 sounded subjectively quieter than the other candidates although the same level was on the measuring microphone. (Measurements were made via ARTA with calibrated Sennheiser Micro).
I think that the feeling arises that the M33 has less power or sounds quieter, because the power amplifiers have extreme control over the bass.
....
The feeling for many that it sounds louder with other amplifiers is due to the fact that simply the control in the bass decreases and that then sounds louder. The same effect is often achieved in the professional PA area. In discotheques or clubs many say that it is much too loud... but if you measure dBa, you'll notice that even at concerts higher values are often reached than in the club. It's simply because in the club, the system is usually poorly adjusted, the medium played is poor, and therefore the distortion is enormously high. At the concert, nothing is overdriven, and the music is usually mixed perfectly. Thus, one has the feeling that the volume is not as enormous as in the club. But is exactly the other way around! I have measured and leveled many systems ...

Source: Link
 

Pragmatic

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Here is a translated excerpt from a German forum:

I am professionally settled in the PA area and CarHifi, so I first set with "pink noise" all amplifiers with the same level so that I had a comparison to listen without volume differences. Here I clearly noticed that the M33 sounded subjectively quieter than the other candidates although the same level was on the measuring microphone. (Measurements were made via ARTA with calibrated Sennheiser Micro).
I think that the feeling arises that the M33 has less power or sounds quieter, because the power amplifiers have extreme control over the bass.
....
The feeling for many that it sounds louder with other amplifiers is due to the fact that simply the control in the bass decreases and that then sounds louder. The same effect is often achieved in the professional PA area. In discotheques or clubs many say that it is much too loud... but if you measure dBa, you'll notice that even at concerts higher values are often reached than in the club. It's simply because in the club, the system is usually poorly adjusted, the medium played is poor, and therefore the distortion is enormously high. At the concert, nothing is overdriven, and the music is usually mixed perfectly. Thus, one has the feeling that the volume is not as enormous as in the club. But is exactly the other way around! I have measured and leveled many systems ...

Source: Link
Yeah that's a good one. And I don't have any reason not to believe it, it makes sense. My older amp obviously had more distortion, but it did have decent control of the bass. And to boot, my particular speakers have lightning quick woofers, with very precise bass - gives the perception that the bass, and SPL, is lower. I have a pretty kickass sub on the side when I just want to shake the house, so it works well, for me.

In my case, it may just be the perfect storm of a lot of acoustic treatments, speakers that sound like they play lower than they do, and now the amp that does the same thing (and that has a very linear volume wheel).

Still wonder why I've only managed to squeeze 70W out of a 900W peak amp though, but must be the speakers. My previous Dali Concept 10's, with 91dB sensitivity and 2x 10" woofers pr speaker, sucked every last drop of juice from my previous amp without issues, and those were rated for less peak power than my current ones. They had that "party bass" factor.
 

SIY

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Yeah that's a good one. And I don't have any reason not to believe it, it makes sense.
There's a LOT of reason not to believe it. Starting with that it's flogging a vague and improbable concept, then has zero evidence supporting it.
 

Calou

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Hi. If you see post #1050 and #1052, would be very neat if you could also run the same dB test, along with posting your speaker sensitivity and distance from the speakers etc.

Well, the guy from the HiFi shop suggested that it may be due to both the volume wheel being more linear than usual, combined with the fact that the amp has very low distortion (so loud listening doesn't trigger that earache you get from cheaper amps). I don't know - max volume has been enough so far, even with Dirac on, but for very dynamic pieces, like classical, it's only just enough. With my old NAD C375BEE, I had the volume wheel at max 40% when listening to classical music (with peaks well over 100dBa). About the same volume as 80% (where 90% is max with Dirac) on the M33. Though, I never tried cranking the wheel all the way, since it's less powerful than the speakers and would blow some expensive nautilus tweeters. For other music genres, I usually stop at between 65-75%, since the loudness war has killed just about all dynamics in modern music.

In your case, with Dirac and tone controls enabled, the loss should be around -17dB in theory - that's definitely a whole lot.

Overall I am happy with the sound too, except when listening to rock and metal. The snare drums sounded magical on the C375BEE, for some reason. No doubt it colored the sound somehow, to my liking.
I will try to run some dB tests, with factory setting which I'm using now and with Dirac.
My speakers are Cabasse Murano Alto and their sensitivity is rated at 89 dB. Listening position is 3.3 meters from speakers.

I can confirm the loss of 15-17 dB range with both Dirac and tone control enabled without measuring since it is pretty obvious and was specified by NAD as 10 dB headroom for Dirac and 6-7 dB loss with tone control.

When turning off dirac I'm not experiencing the 6-7 dB loss with Tone control enabled anymore, very good improvement with the last firmware.

I also suspect that Dirac can add an additional 5dB loss if it is trying to correct big dips in the frequency response as illustrated in the following test:

Here is the illustration:

Question is if the 5dB pre-amp gain of Dirac is part of the 10dB headroom or an additional loss of gain in the master volume??
Dirac provides a lot of freedom to the user, but in that case I would have liked a general setting where I can limit the maximum gain to correct the dips.
 
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fcracer

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I called the dealer where I bought the amp, and asked about power purifiers. They were quite insistant that it can make a positive difference also in Class D and digital amps. I made it clear I already have one, so there was no additional sales in it for them. They had tried a high-end AudioQuest Niagara filter on a NAD M22 (also Class D) and experienced significant improvements.
They also told me that Lyngdorf, another amp manufacturer, officially state that aftermarket power cables don't do anything on their amps. So, manufacturers make many strange claims. If you have a power purifier yourself, you may want to try it on your M33.

I asked about the max volume too, and they said that the volume control on the M33 is very linear, contrary to many older amps where it often is not (lots of gain the first 50%, then very little after that). Their demo model was lent to a customer, so they couldn't check their dB -> % values.
Well, I have a 6 year warranty through the shop, so there's not much to worry about.
I'm using an M33 in a part of the world where the power fluctuates significantly and can be very noisy, however the M33 is dead silent and has no issues. I believe your dealer when he says he can hear a difference, but I don't believe that anyone else can hear that difference. I would highly recommend removing the power purifier as a first step in eliminating any external causes for the issues you're having. Once you have the problem sorted out, you can always bring the purifier back, upon which time, I'd suggest taking measurements with REW before and after introducing the purifier.

In regards to the gain issue you're experiencing, there are a few places that gain can be lost in the M33. Dirac, depending on the measures, can be trying to boost some frequencies such that it brings the gain down to ensure no clipping. When tone controls are engaged, you lose 6db there. Also, depending on the input used, there may be chances there to increase the input levels via the menu or at the source. On my M33, I use Dirac with Bluesound and AirPlay2 as my primary music sources, and at -20db in a 27sqm living room with 90db efficiency speakers, it plays very loud!

I've been using NAD products for over 25 years, and whenever I can't get a problem solved, I reach out to Bob Moran at NAD HQ. He's always been able to help sort the issue out. I hope that people won't bombard him with trivial stuff as I'd hate for us to lose access to him. However, he's always been able to point me in the right direction or get the support I've needed. Good luck with getting your issue sorted out; this is not an inexpensive device, and you should request a high level of service from NAD to get your device working correctly.
 
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SIY

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Bob was amazingly helpful when I had problems. Email and phone, walked me through all the issues.
 

pablolie

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I've been using NAD products for over 25 years, and whenever I can't get a problem solved ...
I do love NAD products -have for many years- but their support network has become awful.

Their new obsession with these touch sensitive power buttons is criminal, because they are temperamental to begin with, and even worse very prone to failure. I have experienced it with 3 different products and in 5 different instances, including the M22. And if it is out of the warranty time. NAD could not care less and they direct you to mom&pop electronic "official service" shops that will charge whatever they want and are typically totally overworked anyhow (odd that). Unless NAD improves on that, I'll never buy their master series again. You have no business selling $3k+ gear if you tell customers to eff off and go to their corner electronics store if their gear breaks after warranty time.

I am a big NAD fan, but that needs to be corrected immediately. Their stuff is class leading and beautiful... until it has an issue. And clearly internet forums unfortunately mention many such instances - like here.
 

Pragmatic

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I'm using an M33 in a part of the world where the power fluctuates significantly and can be very noisy, however the M33 is dead silent and has no issues. I believe your dealer when he says he can hear a difference, but I don't believe that anyone else can hear that difference. I would highly recommend removing the power purifier as a first step in eliminating any external causes for the issues you're having. Once you have the problem sorted out, you can always bring the purifier back, upon which time, I'd suggest taking measurements with REW before and after introducing the purifier.

In regards to the gain issue you're experiencing, there are a few places that gain can be lost in the M33. Dirac, depending on the measures, can be trying to boost some frequencies such that it brings the gain down to ensure no clipping. When tone controls are engaged, you lose 6db there. Also, depending on the input used, there may be chances there to increase the input levels via the menu or at the source. On my M33, I use Dirac with Bluesound and AirPlay2 as my primary music sources, and at -20db in a 27sqm living room with 90db efficiency speakers, it plays very loud!

I've been using NAD products for over 25 years, and whenever I can't get a problem solved, I reach out to Bob Moran at NAD HQ. He's always been able to help sort the issue out. I hope that people won't bombard him with trivial stuff as I'd hate for us to lose access to him. However, he's always been able to point me in the right direction or get the support I've needed. Good luck with getting your issue sorted out; this is not an inexpensive device, and you should request a high level of service from NAD to get your device working correctly.
I already tried removing it. There was no audible difference to the gain. The sound did however become less airy (more noisy). Maybe, in a typical listening room, it won't make much difference on the M33, but in my particular one, it does. I've already taken measurements before and after with REW. There were some minor differences here and there, but nothing worth noting. The one drawback of the purifier I have, is that it only has a 10A fuse - but my listening room only has a 10A fuse too, so any difference in dynamics should be very small. Certainly, I can't rule out that there's a degree of placebo involved here, but the purifier made a major difference to my C375BEE (class AB), and while I am sure the difference is smaller with the M33, it still exists.

My room is acoustically treated, so Dirac hardly does anything, but I have made a NAD curve which boosts bass - I switch between that and a completely flat curve (which automatically boosted bass some places by about 2dB). It gives the sound better focus, which is why I use it. And perhaps slightly less resonances - bass traps in the corner already takes care of most of it.

Never use tone controls, the speakers and amp match well so no need. The gain is exactly the same both when streaming and in Windows (through optical via TV) - already maxed everything in Windows. I'm overall happy with the sound, and for the most part, with the volume level too (usually stop at -24dB unless I listen to classical music). I might check with the shop if I can borrow a Hegel H390, which is 2x250W at 8ohm and class AB, and see if the volume level on that is vastly different.

Appreciate the suggestions though. I might reach out to NAD at some point.

Has anyone here hooked up their M33 to a surround receiver, using the M33 for driving the front speakers only? I know it doesn't have HT bypass, but the volume level isn't the issue for me - it's the audio delay. I finally got the surround set up in Windows so it works, but the front speakers through the M33 has a very long audio delay compared to the surround speakers. I already disabled the 50 ms delay on the line in which connects to the receiver, and I've tried setting the speaker distances at 28 meters for the fronts and 0,3 meters for the surround speakers. Still, we're talking at least a 200ms delay on the front speakers. Which makes it completely unusable. And yes, I also turned off Dirac. If I change a Dirac setting while on the surround input, the delay increases to at least 500ms(!) - until I switch inputs. RCA cable is brand new, decent quality and only 3 meters.

I also tried 2 different sound cards on the PC, and it was the same. So I'm almost certain that the M33 is the culprit. Tried googling this, but didn't find any relevant posts. Would be a damn shame if a $6000 amp can't be combined with a surround receiver..
 

pogo

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Has anyone here hooked up their M33 to a surround receiver, using the M33 for driving the front speakers only?
Yes, currently I delay my surround amps by another 50ms with this unit, because not every decoder/processor is able to do that!:
Link

Regarding surround option, the old M10 should also get a firmware update according to a German hifi magazine. Other Bluesound devices have also been made capable via an update. From a hardware point of view, a firmware upgrade for the M33 should also suffice.
 

pogo

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My room is acoustically treated, so Dirac hardly does anything, but I have made a NAD curve which boosts bass
Here in germany we have also had cases where the rooms were overdamped and this is particularly noticeable with the high damping factor of the M33. You must have optimised your room with an amplifier with a lower damping factor, .... It is highly probable that you are now damping the real audio signal too much. Before, you had tried to eliminate the unwanted swing-out energy in the room of the chassis, which have unnecessarily stimulated the room modes and which is no longer so pronounced! Just remove some acoustically treatments and the result could also improve as with the others;)
 
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SIY

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Here in germany we have also had cases where the rooms were overdamped and this is particularly noticeable with the high damping factor of the M33. You must have optimised your room with an amplifier with a lower damping factor, ....
So you are confused by the same word being used in two different meanings?
 

Pragmatic

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Yes, currently I delay my surround amps by another 50ms with this unit, because not every decoder/processor is able to do that!:
Link

Regarding surround option, the old M10 should also get a firmware update according to a German hifi magazine. Other Bluesound devices have also been made capable via an update. From a hardware point of view, a firmware upgrade for the M33 should also suffice.
Hmm, seems like that would delay the M33 further, since it would be connected between the audio signal going out from the receiver and to the M33 - or am I missing something. My German isn't all that great. The surround receiver gets the initial audio signal, from the PC (or TV), processes it and sends it to the back channels directly, and via Pre Out Front -> RCA to the M33 for the fronts.

I've spoken at great length to the customer service where I bought the M33, and basically been told that this amp is unsuitable as a power amp for surround receivers due to the way it handles analog signals (converts them to digital, processes them, then back to analog, which adds a significant delay). I'm actually seriously considering returning it, and getting possibly a Lyngdorf TDA 3400 instead - but if there truly is a good workaround with the NAD, I'd prefer that. One of the customer service guys did suggest an analog-to-digital converter as a hail mary, but didn't have much hope that it would work since that would introduce audio delays on its own. One of the reasons I bought the amp was to drive the fronts in a surround setup when I watch content with surround encoded, but at the same time have a pure stereo setup for music and such. Was told by the store this was possible with no issues other than having to manually adjust the volume on the M33 each time due to it lacking HT bypass.

I still have some low freq resonances left even after room treatment and Dirac, so I'm 100% sure my room is not overdamped. The treatment is fairly conservative. And doesn't high amp damping factor generally mean a tighter, better controlled bass? To my ears, that's only positive.
 

SIY

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I still have some low freq resonances left even after room treatment and Dirac, so I'm 100% sure my room is not overdamped. The treatment is fairly conservative. And doesn't high amp damping factor generally mean a tighter, better controlled bass? To my ears, that's only positive.
Room treatments effective in bass are quite rare. "Overdamping" in the bass would take a ridiculously large room and ridiculously elaborate measures.

Amp damping factor is pogo's crackpot deal. The differences in actual speaker response between an amp with a DF of 10 versus 50 versus 500 are negligible. Two minutes of calculation on an envelope will demonstrate how incredible (in the literal meaning of that word) claims of sonic differences due to that kind of damping factor change really are.
 

pogo

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My M33 is connected directly to my surround decoder. I have set the minimum possible and Bluesound wanted latency of 50ms for multi-room operation at the M33. This latency I have now inserted additionally between surround decoder and my rear amp using this lip sync corrector. If there were not this restriction of Bluesound, the M33 would be physically able to function without problems in the surround system. I have also already asked for an update, because I don't need multi-room operation all the time, but they resist. There is probably also a f/w hack on the net, but this would lose warranty. Here again an old post from me:
Link

An alternative for you could also be a C399 with bypass. It has also a similar DF to your NAD C375BEE and should sound similarly fuller (subjectively louder) than the M33.
 
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pogo

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I'm 100% sure my room is not overdamped.
Really, for the new setup?
If you wanted to do it right, you would have to start optimizing all over again when you change the speakers or amp. If you have the opportunity to simply back off a few room treatments in this area, give it a try. The result could be, as with others, a subjectively louder result with more details.
You have to keep in mind that the room modes are definitely present, but are excited differently depending on the setup used!
 

Pragmatic

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Room treatments effective in bass are quite rare. "Overdamping" in the bass would take a ridiculously large room and ridiculously elaborate measures.

Amp damping factor is pogo's crackpot deal. The differences in actual speaker response between an amp with a DF of 10 versus 50 versus 500 are negligible. Two minutes of calculation on an envelope will demonstrate how incredible (in the literal meaning of that word) claims of sonic differences due to that kind of damping factor change really are.
I have pretty decent bass traps in each corner which certainly help, but obviously not in the whole freq range. Don't know much about damping factor as I've never even noticed that spec until I bought the M33. All I know is that more is usually better.
 

Pragmatic

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My M33 is connected directly to my surround decoder. I have set the minimum possible and Bluesound wanted latency of 50ms for multi-room operation at the M33. This latency I have now inserted additionally between surround decoder and my rear amp using this lip sync corrector. If there were not this restriction of Bluesound, the M33 would be physically able to function without problems in the surround system. I have also already asked for an update, because I don't need multi-room operation all the time, but they resist. There is probably also a f/w hack on the net, but this would lose warranty. Here again an old post from me:
Link

An alternative for you could also be a C399 with bypass. It has also a similar DF to your NAD C375BEE and should sound similarly fuller (subjectively louder) than the M33.
Oh, you're actually running a separate amp just for the surround channels (and not directly off a surround receiver)? That makes sense. I have 2x 2x150W NAD amps here, and only use one of them currently, so I could try that too (along with one of those lip sync correctors). Since I won't be running surround all the time, that could be a decent workaround for me. Thanks for the tip, man. It's a hell of a workaround, but it wouldn't cost me much, so may be worth it. I was originally getting the C399, but it never came in stock, so I gave up.

My room treatments are fastened to the wall and ceiling, so way too much of a hassle to take them down just to test.
 

SIY

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All I know is that more is usually better.
You hit diminishing returns at 10-ish. The claims otherwise are absolute nonsense, contradicted by basic analysis, and totally lacking in any evidence. So it's not usually something to worry about.

Bass traps are usually limited in range by size and physical space.
 
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