nSUB hum through speakers

Posted by: djs1784 on 05 August 2015

My nSub is connected to PSU of 252 by Naim 2xRCA to Din cable. I suddenly get horrible hum through SL2 speakers even if the sub power is off. Only unplugging the nSub powerline will stop the hum. 

Any idea what is it about? 

Two  two RCA plugs are in Ch 1 & 2 and White and Red respectively.

Earth should be what? This set up was working for long time without problems.

Thank you David

 

 

 

 

Posted on: 06 August 2015 by james n

Have you accidentally changed the ground switch setting on the n-Sub ?

Posted on: 06 August 2015 by Richard Dane

Has the sub cable been damaged by footfall or furniture moving?  Hard to tell without inspecting the inside of the plugs or doing a continuity test.

Posted on: 06 August 2015 by djs1784

Thank you both.

I switched to internal earth and 95% of the hum is gone. Thank you. Must have been knocked by mistake chasing a buzz that is gone.

The cable itself looks like new from DIN to RCA.

I however still get a hum in speakers that is audible in the  room not just close to speakers. Lowering of volume on the nSub below 40 kills it. Any advice on the last 5%. David

Posted on: 07 August 2015 by ChrisSU
Was the last 5% always there? Is it still there if you disconnect the DIN socket?

FWIW my speakers have no hum whatsoever, with or without the N-Sub connected to my Superuniti.
Posted on: 07 August 2015 by james n

Glad you have got most of the hum sorted -  For the remaining 5%, In addition to isolating the sub as Chris mentions,  looking at previous threads i see you have an HDX and naim DAC. Have you any other sources connected to the 252 ?. It's worth checking you have the earth lift set correctly on the DAC (it shouldn't matter on the HDX as the coaxial S/PDIF connection is transformer coupled and so galvanically isolated).

 

When was your kit (252, SC) last serviced ?

 

How does the nSub connect to the mains supply compared to the rest of the kit - same sockets ? another socket elswhere in the room etc ?

 

James

 

Posted on: 07 August 2015 by hungryhalibut
There is clearly some sort of earthing issue here as there should be no hum at all. When I had a nSub it was not an issue. I used phono leads from my then 122x. Could the sub leads be picking up hum from a mains lead?
Posted on: 10 August 2015 by djs1784

Thank you Richard and everybody. I fixed the hum by going internal grounds on both Nsub and the DAC. However my problems started cascading; even with new cable from Naim with impedence correction my Marantz AV8801 which replaced my beloved and recently dead AV2 I could not use the processor with the 252 and after variety of tests including connecting it directly to my 250  amp I am sending the processor to factory for warranty. My HDX will not go past start- ethernet or not. Off to Naim in Canada it goes.

I have connected my Direct TV box to the 252 and noticed that while the panning is correct left to right the balance itself on the 252 is reversed. Turning to left will increase right speaker output. this is true on the DAC input as well. I put the TV box to Tuner and DAC is CD. Only change from my old 100% no problems set up is that AV2 is go. HDX is not on the DAC and I have TV box audio out connected to the 252. This reversed balance happens regardless if I use DIN to RCA, RCA to RCA for the TV box , or disconnect it and my only input is DAC vi HI-Line.

Am I loosing my mind? Any idea where to buy used AV2?