Humming!

Hi Jonners

does the hum/hiss continue if you remove the RA block (and connected devices) from the double socket? 

Is this hum from the speakers, or from the Naim case work?

Simon-in-Suffolk posted:

Is this hum from the speakers, or from the Naim case work?

Good question! Its from the casework on the 282 and 200. Both have just come back from an upgrade and service too.

There is a hiss from both tweeters on rhe speakers.

Turning off the other socket makes no difference.

Just to add, if I crank the volume right up the hum can  then be heard through the speakers. I would never have it halfway in listening mode though for fear of bleeding ears!

I’d be very surprised if the 282 is humming, as hum from the boxes themselves is generated by the toroidal transformers, and caused by mains borne interference. Try turning everything else in the property off and see if the hum stops. If you then turn on one thing at a time you may be able to identify the culprit. 

Jonners, ok there might be two things here... let’s ignore the hum from speakers when you crank up the volume halfway...

Hum from the case is almost certainly from the transformer in your NAP200... they use toroidal transformers for relatively high efficiency, small space and low impedance... all this goodness means they are susceptible to ‘DC on the mains’. When this occurs the laminates saturate easily and hum... if you listen carefully you may  notice the hum from the case work slightly varying at times, and this is due to the differeing DC on the mains.

So what causes this DC on the mains...well its not HF interference. The mains voltage and current cycle around a central point, typically earth potential or 0 volts. If the demand from one side of the cycle is greater than the other then the peaks of the cycle become asymmetrical and an offset is introduced.. this is the so called  ‘DC on the mains’ that is referred to.. and an efficient transformer might saturate if fed by such a waveform. This offset can be caused by unbalanced loading on your supply phase and/ or in your house. Some switch mode powersupplues and primitive current controlling devices like in hair drivers can cause this.

The solution... not that easy... but you can buy a commercial DC mains remover.. they tend to work well and most of the good ones are rated to a certain current and generally benign on performance. An other option is to use an isolation or balanced mains transformer... this will be expensive and take more space.. bit if large enough might make sense if you have many devices affected by this.

Now if you fix this, you may find the hum when you crack the volume up reduces.. or may be from another reason such as input earth loops, or poor source power regulation. A saturated transformer output waveform tends to look horrendous, so your NAP powersupply has to work harder to smooth things out... best try and remove it or most of it.. and then go from there.

My humming transformer responded well to an Isol-8 Powerline Axis -- this is a powerstrip with DC blocker but no mains filtering/conditioning. Not cheap but worth the money if hum drives you mad...

• I also use an Isol8 Axis. With an XS2 and now a SN2. As said above not cheap but effective and simpler than having a dedicated mains point. 

Bob F

The first test I would try is to disconnect all components from the 282 and listen.  If the hum goes away, plug each source into the 282 individually, then add them all back, one at a time, listening to the effect with each addition.

In my case, my Naim CD5X seemed to cause the hum; it actually revealed the earth loop caused by my TV Cable service.

I inserted a ground loop isolator between my AV amp and NAC to resolve — cheap and effective.

Nick

NickSeattle posted:

The first test I would try is to disconnect all components from the 282 and listen.  If the hum goes away, plug each source into the 282 individually, then add them all back, one at a time, listening to the effect with each addition.

In my case, my Naim CD5X seemed to cause the hum; it actually revealed the earth loop caused by my TV Cable service.

I inserted a ground loop isolator between my AV amp and NAC to resolve — cheap and effective.

Nick

Great advice here. Try to isolate the issue BEFORE throwing money at it.  You may succeed or may not, but it's worth the effort to as Nick says break it all down and add back components one by one.

This same process goes for home network issues.  If there is an offending device, often the only way to identify it usually is to add items in one at a time until the issues happens again.

All very good advice one and all, it's much appreciated. I turned off the white goods in the kitchen and the hum was reduced. If it wasn't for the fact they're all hard-wired into a fitted kitchen (so no plug sockets), I'd get an Isotek plug-in to create a dead spot around them but that's not possible.

I will try source removal advice to see if one of my components is causing the offending him as well.

I know what I'm like so I'll probably chuck money at it and take the belt and braces approach, buying an Isol-8 just to be sure.

Cheers guys,

Jon

Jon,

Especially when there might be more than one problem, “divide and conquer” is the best strategy.

Goes without saying, I suppose!

????

Jonners posted:

I know what I'm like so I'll probably chuck money at it and take the belt and braces approach, buying an Isol-8 just to be sure.

A good dealer will let you have an Isol-8 to try before you buy. I had mine for a week to be sure that the hum was killed before swipping the credit card.

Hi,

Maybe worth getting a competent 'sparky' round and just go through all connections on your mains supply (everything). Anything could be causing the hum, I would start from there first.

Stephen Tate posted:

Hi,

Maybe worth getting a competent 'sparky' round and just go through all connections on your mains supply (everything). Anything could be causing the hum, I would start from there first.

I'm not ruling anything out, that would be cheaper than an Isol8 for sure. It is a new build though so I would expect everything to have been wired up correctly to meet safety regs, though probably using the cheapest cabling possible.