Supernait2 and speaker noise

Bart posted:

Clearly something is amiss.  My SN2 generates just the slightest hiss when no source is playing. Nothing more untoward than that.

It is a very slight hiss, and as I said I'm not too worried as it doesn't seem to affect SQ. The funny thing is that I can hear it through the speakers with MUTE on (obviously I can no longer hear the music).

And, Richard, I've checked the polarity, the mains cables (Powerlines), the mains block (Musicline) - the earth seems ok, the set-up is very recent anyway and was checked last year. I'm having some major building work done in September, I will ask the electrician to have  another look at it. And the CDX2 has never been opened, I got in touch with the previous owner and the dealer through whom I bought the CDX2.

Other CDX2/Supernait 2 owners may have come across the same issue?

A slight hiss is fine.  I thought the issue here was a constant hum through the speakers?  That usually indicates a issue somewhere - either an earthing issue such as an earth loop, or else a cabling issue, or maybe even a fault with something within the system.

Out of interest, where is the CDX2 / PS located in respect to the SN2 ?

A good question from James...

Yes, my use of the word 'hum' was misleading - it's only a faint noise - but I was under the impression that the mute button effectively cut off any signal going to the speakers, not just the music itself, but also any residual noise, so that the speakers were totally isolated from the amplifier and the source. And the noise can only be heard when the source is on - which I find strange... but I know little about the innards of those wonderful machines.

The CDX2 sits on its own shelf, with the SN2 immediately below, on another shelf. The power supply is at the bottom of the rack.

You'll have a small amount of hiss whether mute is engaged or not. As you rightly say, the mute switch doesn't isolate the speakers from the amplifier -  the input selection stage is effectively disconnected from  the power amplifier stage when the mute button is engaged.

How much you will notice this is dependent on the sensitivity of the speakers and how close you are to them. As others have said, nothing to worry about. I picked up on the hum bit but if that was not the case then it looks like all is fine. 

SamClaus posted:

Yes, my use of the word 'hum' was misleading - it's only a faint noise - but I was under the impression that the mute button effectively cut off any signal going to the speakers, not just the music itself, but also any residual noise, so that the speakers were totally isolated from the amplifier and the source. And the noise can only be heard when the source is on - which I find strange... but I know little about the innards of those wonderful machines.

The CDX2 sits on its own shelf, with the SN2 immediately below, on another shelf. The power supply is at the bottom of the rack.

 

It usually only cuts off the input to the preamplifier, or some part of the preamp or (possibly) the output of the preamp - so you still have whatever noise (hiss/hum) that is produced by either the amp and/or the preamp.  

Since my last report, i have disconnected my subwoofer from the system.

I have removed the sub out cable ( 1.5 meter long Mogami 2497 ) completely and set it aside.

The Mogami 2497 cable was running from the SN2 and along the back of the rack with other cables and meeting the subwoofer plate amplifier at about 1.15 meters distance away.

I am getting now used to music w/o the subwoofer.

The noise is diminished very much and does not disturb me any more.

Technically qualified and experienced members may enlighten as to why a good cable like the Mogami 2497 should contribute to this ??

was this really the cause ?

My ears tell me so - but technically it should be possible to run a cable from the SN2 sub out to the subwoofer without interference ?

I have not re-inserted the cable back again to check for noise.

I might do this and re-verify sometime..

Maybe i might try to connect the sub like REL does - from the back panel of the SN2 to the plate amp - high level i/p

Thats a much shorter distance..

best regards

mpw

I had this issue (with SN2) when I introduced an Uptone Audio USB Regen into my system... it was a very high pitch screeching noise that came through at low level and didn’t change regardless of the volume. After much messing about and experimentation I connected up the ground pin on the back of the SN2 to a mains earth (if that’s the correct terminology?) and the noise disappeared. I had an electrician friend make up a ground cable for me to do this which plugged into the mains sockets. Turns out it was some sort of grounding issue... I got there in the end but the Uptone Audio USB Regen was soon (unfortunately) dispersed of. 

@mayor west

thank you

this is interesting information

The closest device to my SN2 is the Lehmann audio phono stage which has a ground pin which is connected to the TT ground

Does the forum think i can run a short small wire from the SN2 ground pin to the ground of the phono stage ?

will there be any hazards ?

Note - I did not mention the TT itself as a 2nd source as my TT is under repair for the last 2 months so effectively all my observations are with 1 source - CDP only

regards

mpw posted:

Since my last report, i have disconnected my subwoofer from the system.

I have removed the sub out cable ( 1.5 meter long Mogami 2497 ) completely and set it aside.

The Mogami 2497 cable was running from the SN2 and along the back of the rack with other cables and meeting the subwoofer plate amplifier at about 1.15 meters distance away.

I am getting now used to music w/o the subwoofer.

The noise is diminished very much and does not disturb me any more.

Technically qualified and experienced members may enlighten as to why a good cable like the Mogami 2497 should contribute to this ??

was this really the cause ?

My ears tell me so - but technically it should be possible to run a cable from the SN2 sub out to the subwoofer without interference ?

I have not re-inserted the cable back again to check for noise.

I might do this and re-verify sometime..

Maybe i might try to connect the sub like REL does - from the back panel of the SN2 to the plate amp - high level i/p

If your sub has a high level input, run the cable from the terminals on your speakers rather than the amp. Naim amps generally prefer this, and there is no need to use fancy speaker cable, so it is inexpensive. Maybe easier for you to route these cables clear of others too. 

Hi mpw,

Yes it did seem like I had introduced some sort of ground loop into the system. I noted that even after removing the Uptone Audio USB Regen, there was still a low grade hum (not previously noted before). Putting the cable back in place from the ground pin on the SN2 again removed this. I normally use a MacMini but interestingly there is no need for the ground pin the be hooked up on the SN2 (no hum/noise) if I use a MacBook as my main source, as long as it is running from battery and isn’t connected to mains power. 

[@mention:1566878603926433] and beachcomber: thanks for your replies - you learn something new everyday...

ChrisSU posted:

mpw posted:

Since my last report, i have disconnected my subwoofer from the system.

I have removed the sub out cable ( 1.5 meter long Mogami 2497 ) completely and set it aside.

The Mogami 2497 cable was running from the SN2 and along the back of the rack with other cables and meeting the subwoofer plate amplifier at about 1.15 meters distance away.

I am getting now used to music w/o the subwoofer.

The noise is diminished very much and does not disturb me any more.

Technically qualified and experienced members may enlighten as to why a good cable like the Mogami 2497 should contribute to this ??

was this really the cause ?

My ears tell me so - but technically it should be possible to run a cable from the SN2 sub out to the subwoofer without interference ?

I have not re-inserted the cable back again to check for noise.

I might do this and re-verify sometime..

Maybe i might try to connect the sub like REL does - from the back panel of the SN2 to the plate amp - high level i/p

If your sub has a high level input, run the cable from the terminals on your speakers rather than the amp. Naim amps generally prefer this, and there is no need to use fancy speaker cable, so it is inexpensive. Maybe easier for you to route these cables clear of others too. 

too messy it is.. ChrisSU

My speakers have a zobel n/w ( RC network ) externally attached to the speaker terminals.

have been thru this on another thread started by me on the subwoofer connections to a Naim nait 5i-2

I rather prefer it from the back terminals of the SN2

regards

mpw