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NAD C 368 has high pitched tone at all times?

Freighter

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So I recently got a NAD C 368, which uses a Hypex UcD amp. However I’m having a problem where I could swear that there’s a high pitched noise coming out of the speaker tweeters at all times. I find this even audible when music or movies are playing, during quiet passages.

I’m trying to figure out what could be causing it and if it’s ‘normal’ and intrinsic to the amp or if it’s a fault?

I’ve tried turning on the amp with no wires attached at all, except for power and speakers, and the noise is still there.

When turning the amp off, it immediately goes away.

It’s like when I put my ear to the tweeter it’s mostly just a slight hiss, but in the background is a high frequency tone or squeal or something like that.

I feel like it’s so quiet I shouldn’t be able to hear it at my seated position, but somehow I can. It’s almost like the room acoustics amplify that specific sound.
 

Doodski

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I would start a warranty claim on it or try to return it for another like unit.
NAD claims.>>>
"The power supply is capable of 80 watts continuously and over 120 watts instantaneously to allow for short-term musical transients. It can operate with any AC mains voltage from 100 to 240 volts and provides pure DC power to all the various stages of the C 368. This highly efficient supply also provides near perfect regulation of voltage across a wide range of conditions and provides a solid noise-free foundation for the amplifying stages."
 

valerianf

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Class D weakness: hiss prone.
 

wwenze

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It’s like when I put my ear to the tweeter it’s mostly just a slight hiss, but in the background is a high frequency tone or squeal or something like that.

I feel like it’s so quiet I shouldn’t be able to hear it at my seated position, but somehow I can. It’s almost like the room acoustics amplify that specific sound.

Check if the high pitch noise is coming from inside the amplifier.
 

valerianf

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"I could swear that there’s a high pitched noise coming out of the speaker tweeters at all times"
It is the definition of the hiss sound.
 

MaxwellsEq

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"I could swear that there’s a high pitched noise coming out of the speaker tweeters at all times"
It is the definition of the hiss sound.
Read what he said again. He said he can hear a faint hiss AND a high pitched tone
 
OP
F

Freighter

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Check if the high pitch noise is coming from inside the amplifier.
Yea. There is, near the power socket.

Wouldn’t some noise be expected though, when you put your ear to it?
 

Count Arthur

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NoMoFoNo

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In any event this whine will drive you nuts. If you can return the unit I would do so. If not, I would contact NAD and check their warranty and/or service terms. The C368 is a serious and pricey piece of gear that should perform at a high level.
 

KR500

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power issue ?
Did you try a different outlet or using a power conditioner
What else shares that circuit besides the stereo equipment
 
OP
F

Freighter

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Definitely get it replaced. I own a C 368 as well and It’s dead silent at the tweeter and at the amplifier itself. You really shouldn’t be hearing anything like you described.
I do have particularly sensitive speakers. Klipsch /102dB - I do know those numbers are probably not quite accurate, but they should still be more sensitive than most. I would expect some amount of speaker hiss to be audible - at least I've never heard an amp that doesn't have it. Though I've tried limited amps... My Marantz AVR, a Topping PA5 II and the NAD C 368 all have some audible hiss. Though only the NAD has the audible high frequency noise. Can I ask what kind of speakers you have?
power issue ?
Did you try a different outlet or using a power conditioner
What else shares that circuit besides the stereo equipment
No I haven't tried using a power conditioner. I have tried a different power socket. It's connected to its own socket in the wall so it's not a power strip or anything like that. As far as the circuit goes... well, lots of stuff I suppose? I don't exactly have any other options, I don't have a separate circuit just for the amp.
 

KR500

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My speakers are Seas with 94 db sensitivity and my Nad 316BEE V2 has some noise only if I put my ear next to the speaker and turn the amp up past 3/4 to maximum.
Our former home had a separate electrical circuit for only my stereo, but not the house we just moved to.
My Nad Amp remote stopped functioning after 5 or 6 months and both the Audio Advisor retailer and Nad Warranty people were great.
Shipped me a new remote after I contacted them
 
D

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I do have particularly sensitive speakers. Klipsch /102dB - I do know those numbers are probably not quite accurate, but they should still be more sensitive than most. I would expect some amount of speaker hiss to be audible - at least I've never heard an amp that doesn't have it. Though I've tried limited amps... My Marantz AVR, a Topping PA5 II and the NAD C 368 all have some audible hiss. Though only the NAD has the audible high frequency noise. Can I ask what kind of speakers you have?

No I haven't tried using a power conditioner. I have tried a different power socket. It's connected to its own socket in the wall so it's not a power strip or anything like that. As far as the circuit goes... well, lots of stuff I suppose? I don't exactly have any other options, I don't have a separate circuit just for the amp.
You shouldn't experiment with all this. You should just claim your warranty.
 

OldTimer

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Yea, I returned it and am using a Topping PA7 II instead. That one’s dead quiet at the listening position and doesn’t have any weird sounds.
What did you find? Is it better than your normal NAD?
 
OP
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Freighter

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What did you find? Is it better than your normal NAD?
I also returned the Topping. It was whisper quiet and it sounded good, but non-science based feelings got in the way.

I know most people on the forum probably wouldn’t agree, but I could swear it sounded differently every time I sat down to listen to music. Mostly I felt like sometimes the mids were very recessed, like voices suddenly sounded audibly quieter.

I know that shouldn’t happen based on the measurements for this device - it should be pretty much perfect.

I also felt like when playing loud, it sounded really messy as if it was distorting. However I hooked it up to an energy meter and it wasn’t nearing its maximum output. So I don’t know, I could swear it sounded really rough at a certain volume.

There’s an Andrew Robinson video about cheap chi-fi and he said he measured the frequency response of the speakers multiple times, and he gets a different result every time with these Chinese amps. That sounds like a ridiculous thing and it shouldn’t be true. However I also thought that - subjectively - the topping sounded different every time.

I’m now back to my old Crowne XLS1052, which according to the measurements should be pretty bad, but sounds great to me. The one downside to that one is that it has an audible hiss on my speakers. However the hiss sounds like white noise, so unlike the NAD, you tune it out after a while.
 

NoMoFoNo

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Sighted listening is powerful and the audiophile world has convinced many of us that amps must be large, usually heavy, expensive, things to be coveted and paid dearly for. Not sure how big your room is or how far away you sit from the speakers, but at least a couple of the amps you noted would absolutely smash your hearing unless you listen in a very large room.

It might be fun to get a hold of another more traditional HiFi amp, maybe another NAD unit, and blind test it against a PA7. I'd bet money (well, maybe) that you'd struggle to tell the difference.
 
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