NAD 752-Sub Hum


New member
Username: Hab

Post Number: 1
Registered: 02-2004
Just purchased an NAD 752 & paired with my Athena AS-F2 Floors, AS-B2 Rears, & AS-C1 Centre I am in heaven. The sound is as good as it gets, rich, clear & warm.
But when i try to hook up my Athena Sub I get this really loud hum. Even with a $50 sub cable, as soon as I put the connector into, or for that matter even close to the sub in on the receiver i get this buzz & squeal. I've moved the cable away from any other wires & moved in all directions. Sometimes it dies down a little but it never goes completely. Please help me out here. The last thing i wanna do is return this dream receiver. Any ideas?

Unregistered guest
My HSU sub came with a "cheater plug" and instructions that if a hum occurred...use the plug at the wall socket. It worked!

Unregistered guest
Hi Paul:

I have exactly the same system, with the AS400 sub. No hum what-so-ever. Sub is plugged into a separate wall outlet from the receiver.

And just a note of caution, only plug in one connector to the back of the sub. There are two connections, and the fellow selling me my sub told me to plug into both via splitter. He was incorrect.

Hope this helps.

Interested to know if you find the sound slightly bright?


Silver Member
Username: Hawk

Post Number: 350
Registered: 12-2003

I don't know if you are the person who wrote me a PM on the same problem or not, but I will repeat what I said there.

Sub hum is almost always a grounding problem. Start by making sure that both ends of the sub cable are fully seated. Some sub cables use slightly oversized plugs that make it hard to push them in all the way. Consequently, a good connection is not made and there is a hum. So, really push those little guys in and make sure the plug is fully seated into the jack.

If that does not solve the problem, Monster Cable offers a product that I have had very good luck with solving some hum problems for friends. It is called the Monster Cable MP-SW200, which is a small wall socket mounted surge suppressor and power filter (has two outlets). MSRP is $49.95, but I have seen it for under $30. Check it out here:

I also completely agree with TC that you should use only one jack--forget using a "Y" to conneect both.

Good luck!

New member
Username: Hab

Post Number: 2
Registered: 02-2004
Thanks guys for all your suggestions.

I have the sub plugged into a different outlet, both connectors are fully in (only one on the sub itself)& still the hum. I used just a regular audio wire & that reduced it a lot but it is still clearly heard through all five speakers. This might sound really strange but I get the hum even without the sub plugged in to an outlet or even connected at the sub...really-no sub connected or near my system & it happens. I can take the cable only, walk to the receiver only & as soon as i touch 1 connector to the sub in on the receiver only the hum starts & stays even if I plug it all the way in. If I move the cable around it increases & decreases a little & get this....I can hear radio stations through all my speakers.
I have spoken to the service guy where I bought the receiver & he suggested removing the cable in from my digital cable box to see if that helped ( a filter would fix this if so)...but it didn't. He can't explain what is happening & said he would drop by & have a look if I wanted.
I am starting to think that it is that dreaded NAD hum that I have heard so much about on this board. I have heard firmware mentioned here also. What is that?
Once again, thanks for the suggestions.

Unregistered guest

I believe you have a grounding issue.

If I understand correctly, it is not the sub, but rather the piece of wire, acting as an antennae, that is causing the hum.

Is the outlet that the receiver is plugged into properly grounded? Is there a source of noise, ie. compressor from a fridge etc., sharing the same line to the breaker.

Here's a goofy idea for you. Get an extension cord and plug the receiver into a GFI outlet in your bathroom. Make sure nothing else is connected to the receiver except the speakers. No DVD etc. and no sub. Let me know what happens.

My thoughts are that GFI are grounded well and also will not share a line with the fridge or any other high current device. Just a thought and it's easy enough to try without ripping out the receiver.


Ben Winter
Unregistered guest

I recently had a similar problem with my NAD T763. I was hearing humming and a radio station from my surround sounds. I tracked the hum down to the sub cable. (You can read about the whole experience here: The cable was acting as an RF antenna and drawing in Radio Frequency Interference (RFI), then the receiver was amplifying the sound and sending it to my surrounds. I solved the problem with a Ferrite Choke Core ($5.00 at Radio Shack: You just clip the choke around the sub cable near the receiver. It also helped when I coiled the excess sub cable to reduce the surface area.

I did find that the RFI occured when I touched the cable anywhere near the sub out, my guess is that the area is a sensitive area of NAD receivers.


New member
Username: Hab

Post Number: 5
Registered: 02-2004
Thanks for the suggestions. I did purchase then Choke at Radio Shack but no improvement. By using a cheap audio cable I do get rid of 98% of the noise. I am plugged into an extension cord so that's my next thing to look at.
Now I have another annoying problem. I jus ran an S-Vid cable from the S-Vid/Monitor out on the unit to my TV & the picture is horrible. The OSD bleeds also. Ani ideas on that?
« Previous Thread Next Thread »

Main Forums

Today's Posts

Forum Help

Follow Us