Nad C 658 - loud hum when played via cyrus amp and Revel speakers

brazim01

Active member
May 18, 2020
6
3
25
Hi all, first time posting so apologies if this is in the wrong place, I'll try to be as detailed as possible.

I have a Cyrus 6XP amp paired with some Revel Concerta 2 speakers. The inputs are a Cyrus CD player and Rega P3 turntable. The speakers and turntable are relatively new and I've been using them regularly with no issues and great sound.

I took delivery of a NAD c 658 streamer today. I've set it up as an input to the Cyrus amp so I have digital options for streaming. Unfortunately whenever I switch to the NAD input there is a loud hum coming from the speakers. I've tried changing the input, made sure all of the connections are sound. I've tried the altering the volume on the NAD and on the Cyrus but nothing seems to fix it. The hum is only affected if I change the volume on the Cyrus amp so can only be eliminated if I turn the amp right down which makes the music inaudible. If I turn the NAD up significantly I get crackle from the speakers too.

Does anybody have any suggestions as to what might be causing it? Any help appreciated.

Thanks,
 

brazim01

Active member
May 18, 2020
6
3
25
So the CDP is totally hum-free?
And you've tried the NAD, using the same, good interconnection leads, into every available line input on the amp ?
CD player sounds good and no hum, tried two sets of good quality interconnects in all of the inputs on the amp.
 

Gray

Well-known member
Nov 27, 2015
561
284
5,270
Can you go into the setup menu of the NAD and set the output to fixed?
(So that your volume level is controlled only by the Cyrus' volume control)

Note that your Cyrus wants a fixed level from the NAD - the crackle when you turned the NAD volume up was due to it overloading the Cyrus inputs.
 
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brazim01

Active member
May 18, 2020
6
3
25
You've got the symptoms of a hum loop. The NAD looks like it's got a mains earth but the Cyrus hasn't, so it's slightly mysterious.
Can you use a soldering iron?
I wouldn’t say I’m a dab hand but I know a man who is so could do some soldering if necessary
Can you go into the setup menu of the NAD and set the output to fixed?
(So that your volume level is controlled only by the Cyrus' volume control)

Note that your Cyrus wants a fixed level from the NAD - the crackle when you turned the NAD volume up was due to it overloading the Cyrus inputs.
Thanks, I'll try this today
 
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brazim01

Active member
May 18, 2020
6
3
25
Can you go into the setup menu of the NAD and set the output to fixed?
(So that your volume level is controlled only by the Cyrus' volume control)

Note that your Cyrus wants a fixed level from the NAD - the crackle when you turned the NAD volume up was due to it overloading the Cyrus inputs.
Hi, tried the fixed volume but no joy. Contacted the retailer and they think it’s a fault so it’s going back today. Thanks for all your help
 
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