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Should an amplifier (NAD M33) be completely silent?

LP1313

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Good evening,

I recently started my audio journey and it’s been a joy! I’m struggling with a (maybe silly) beginner-question that I hope you can help me with. It’s my first post, looking forward to your replies.

I have a NAD M33 and I’m happy with it. Recently I noticed that it makes a soft buzzing sound, which is only audible when I put my ear close to, right above it (can’t hear it at the listing position).

To prevent getting fixated on it, I’d like to understand if it’s normal for the device to make a soft buzzing sound or if it should basically be completely silent?

Your wisdom is more than welcome.
Thanks and nice evening!
 

HarmonicTHD

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Good evening,

I recently started my audio journey and it’s been a joy! I’m struggling with a (maybe silly) beginner-question that I hope you can help me with. It’s my first post, looking forward to your replies.

I have a NAD M33 and I’m happy with it. Recently I noticed that it makes a soft buzzing sound, which is only audible when I put my ear close to, right above it (can’t hear it at the listing position).

To prevent getting fixated on it, I’d like to understand if it’s normal for the device to make a soft buzzing sound or if it should basically be completely silent?

Your wisdom is more than welcome.
Thanks and nice evening!
I would say. Don’t worry about it. What you hear most likely is the slight buzzing of the power supply as in many electrical devices.

Put your ear next to your speakers when no music is playing. If you don’t hear the buzz coming out your speaker you are fine.
 

voodooless

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Looking at the review:


There should not be a buzzing. Is it with all sources?

As @HarmonicTHD said, don’t worry too much.
 
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LP1313

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I would say. Don’t worry about it. What you hear most likely is the slight buzzing of the power supply as in many electrical devices.

Put your ear next to your speakers when no music is playing. If you don’t hear the buzz coming out your speaker you are fine.
Thanks for your quick reply, much appreciated. Sounds reassuring. I’ll try to not think about it anymore and enjoy the music instead ;-)
 
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LP1313

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Looking at the review:


There should not be a buzzing. Is it with all sources?

As @HarmonicTHD said, don’t worry too much.
Thanks for reference, I’ll read it.
It’s a soft constant buzz, regardless of which source. Indeed might just be the power supply…
 

Capitol C

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Almost certainly the transformer. If you can't hear it while listening, and there is no buzz or hum through the speakers, you are fine. My 1960s AR-AU amp gives hiss through the speakers when the volume is up to a scary level, consistent with the S/N ratio of equipment at that time. I can't hear it at safe listening levels, and certainly can't hear it when I play music, so I just enjoy the vintage system. My newer Yamaha is silent. Neither of them have transformer hum.
 

voodooless

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Ah wait, it’s the unit itself, not the speakers :facepalm:

Yes, that should be transformer buzz. It might get worse depending on the use of some other home appliances. Generally this means there is some small DC offset on the mains. One can buy DC blockers to get rid of this. But als long as the volume is this low, I would not worry about it.
 
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LP1313

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Good morning and thanks again guys for your advice, much appreciated.
Have a nice day!
 

restorer-john

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Yes, that should be transformer buzz. It might get worse depending on the use of some other home appliances. Generally this means there is some small DC offset on the mains. One can buy DC blockers to get rid of this. But als long as the volume is this low, I would not worry about it.

The M33 has a switch mode power supply with what looks like fower factor correction on the front end. It should relatively silent. The actual transformer is a high frequency unit and there's no chance it will 'buzz'. DC on the mains is irrelevant to this type of supply.

That said, various eddy currents and general steel panels etc can make for an amp of this type to buzz. It could be loose windings on one of the AC chokes on the primary side.

NADM33SI_O_5-copy.jpg
 

voodooless

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The M33 has a switch mode power supply with what looks like fower factor correction on the front end. It should relatively silent. The actual transformer is a high frequency unit and there's no chance it will 'buzz'. DC on the mains is irrelevant to this type of supply.

That said, various eddy currents and general steel panels etc can make for an amp of this type to buzz. It could be loose windings on one of the AC chokes on the primary side.
Ah, good info. I didn't look at the inside pics ;) So don't buy a DC blocker then, it won't help.
 
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PBN94

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Hello,
The NAD M33 is known to suffer from slight Coil whine problems.
I had one and had to go through the service department.
In fact they put some white paste on some parts of the power supply and since then no more problems.
 

restorer-john

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The NAD M33 is known to suffer from slight Coil whine problems.

It's surprising how many coils do whine in SMPSs. Makes you wonder if anyone ever tested them at idle, normal operation and full power. Buzzing/Hum (LF) is rare in an SMPS, but perfectly normal in EI/Toroids etc.

I have an Audio Research SP-8 preamplifier to repair with so much transformer noise I can hear it from 5 ft away...
 

voodooless

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I have an Audio Research SP-8 preamplifier to repair with so much transformer noise I can hear it from 5 ft away...
My dual mono UcD400 also hums like crazy sometimes (due to DC). I wonder if flipping one of the toroids upside-down would lower the noise because the vibrations would cancel out?
 

PBN94

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In fact, the M33 is so quiet and with an excellent signal-to-noise ratio that you can hear a very slight bzzzzz when listening carefully.

I was using Nuprime equipment, which had some hiss in the speakers... so I was aware of this kind of problem. :rolleyes:

A bit of paste in the right place, capacitors / power chokes under a small blue plate that we see on the front right on the picture above.
And everything was good !
 

Sal1950

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I have 5 30yo+ Adcom amps running in my multich rig and none of the units physically buzz or hum.
Plus, I can stick my ear in the horn of my JBL speakers and hear no hisssssss ?
SO, Where's the progress? LOL
 
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LP1313

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It's surprising how many coils do whine in SMPSs. Makes you wonder if anyone ever tested them at idle, normal operation and full power. Buzzing/Hum (LF) is rare in an SMPS, but perfectly normal in EI/Toroids etc.

I have an Audio Research SP-8 preamplifier to repair with so much transformer noise I can hear it from 5 ft away...
Thanks for additional insights everyone.
I just went to a local dealer who has a M33 on display and this one produces the same soft buzz, so I guess it’s nothing really to worry about. Now time to enjoy the music again ;-).
 

PBN94

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I 5 have 30yo+ Adcom amps running in my multich rig and none of the units physically buzz or hum.
Plus, I can stick my ear in the horn of my JBL speakers and hear no hisssssss ?
SO, Where's the progress? LOL
The Nuprime are known for this breath, they sound good but I could not hear anything else...
The NAD M33 is not the same, we are closer to a computer noise that buzzes.
Since I came back on hybrid AB class with a tube input stage and for the moment all is well !
 

SIY

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I have an Audio Research SP-8 preamplifier to repair with so much transformer noise I can hear it from 5 ft away...
I have a Bryston power amp like that, probably magnetostriction of the power transformer laminations. One day when I have more time, I'll damp the hell out of the power transformer and put it back in service.
 
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PBN94

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Thanks for additional insights everyone.
I just went to a local dealer who has a M33 on display and this one produces the same soft buzz, so I guess it’s nothing really to worry about. Now time to enjoy the music again ;-).
There is a technical note about this problem at NAD.
It was out of the question for me to stay with this disturbance at home :(
You don't have a NAD technical station near you?
The technician took less than 15 minutes to disassemble, repair, reassemble and test.
It was free of charge, the only problem is the time wasted to do it.
 
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LP1313

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There is a technical note about this problem at NAD.
It was out of the question for me to stay with this disturbance at home :(
You don't have a NAD technical station near you?
The technician took less than 15 minutes to disassemble, repair, reassemble and test.
It was free of charge, the only problem is the time wasted to do it.
Good point, cheers, I’ll look into it.
 
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