Transformer hum - what to do?

As far as my experience is concerned, you have three sensible options (I say sensible because there are people, in this world, who would keep the system and change the house): a), a power regenerator, like PSAudio or the like; b), accept that the thing is Naim-inherent and live with it; c) change brand.

Best

M

Max_B posted:

As far as my experience is concerned, you have three sensible options (I say sensible because there are people, in this world, who would keep the system and change the house): a), a power regenerator, like PSAudio or the like; b), accept that the thing is Naim-inherent and live with it; c) change brand.

Best

M

Did you deliberately omit the option of a DC blocker?

Re b) accepting it is inherent when with Naim when bad mains is causing it doesn't make it acceptable in use if it is interfering with enjoyment of the music or the room!

And re c), it is important to be aware that it is not a phenomenon unique to Naim, and if the cause is a mains problem there is no guarantee that choosing another make will avoid a transformer hum, though very likely different brands will differ in their susceptibility,, and indeed different models (also very likely there will be variation within the Naim brand or possibly even between different examples of the same model).

As for moving home, that of course is a balance for the individual, as in how critically important to enjoyment of the home might be enjoyment of the music unfettered by annoying hum vs whatever other factors may be at play...  but if someone has a loved but susceptible piece of kit, then take it with you when home hunting!

 

Max_B posted:

As far as my experience is concerned, you have three sensible options (I say sensible because there are people, in this world, who would keep the system and change the house): a), a power regenerator, like PSAudio or the like; b), accept that the thing is Naim-inherent and live with it; c) change brand.

Best

M

d)  Fit a DC blocking filter in the supply to the audio system.
e)  Get a professional electrician to fit a large isolating transformer near the consumer unit (7500VA for typical UK mains circuits).

Huge posted:
Max_B posted:

As far as my experience is concerned, you have three sensible options (I say sensible because there are people, in this world, who would keep the system and change the house): a), a power regenerator, like PSAudio or the like; b), accept that the thing is Naim-inherent and live with it; c) change brand.

Best

M

d)  Fit a DC blocking filter in the supply to the audio system.
e)  Get a professional electrician to fit a large isolating transformer near the consumer unit (7500VA for typical UK mains circuits).

Huge - as per my previous post one of the power supplies is now at my dealers and suffered the same hum there. As you say all transformers hum to some degree but I never heard it before (before in my previous house and before the servicing/DR upgrades) and the noise from the NAP300 PS in particular but all three cumulatively can be very distracting. I'll wait for more feedback from my dealer but if it turns out that it is purely down to the mains then I will have to weigh up the whole situation and look at the various solutions being offered.

I don't want to give up on this system as I absolutely love it so as you suggest some sort of DC filtering sounds like a place to start. A large isolating transformer near the consumer unit would have been a possibility in times gone by as that is all situated in what used to be the garage - this has now been converted into another living area within the house.

Innocent Bystander posted:

 

As for moving home, that of course is a balance for the individual, as in how critically important to enjoyment of the home might be enjoyment of the music unfettered by annoying hum vs whatever other factors may be at play...  but if someone has a loved but susceptible piece of kit, then take it with you when home hunting!

 

 A better words sequence to regain some sanity here would be: 'As for moving home, that of course is for the unbalanced individual..'

Chrissw19 posted:

Hi Markah, you have a great system! I suffered from a randomly humming Hicap DR and similar on the 300PS but less frequently. It was quite annoying so I've bought an Isol-8 DC blocker (high current version) on an auction site just to see if it was going to work and it did, the humming is completely gone! The hicap was also suffering from a constant very low level hum that has disappeared. 

That sounds promising - I see they do an "Axis" range for DC-blocking, was it something from that?

I don't want to spoil your promising expectations Markah, but I have less positive experience with dc-blockers.
About 2 years ago I tried 2 Nait 5si's and they both sufferd badly from transformer hum. I had the chance to try two DC blockers. One from Supra and the so-called 'AH! DC-offset killer'. Both indeed killed the hum, but.... unfortunately, also the sound.

Although both to a different extend, they immediately softened the treble, and dynamics, making the music sound dull and lifeless.
Perhaps a more expensive dc blocker like the Isol-8 Axis won't harm the sound-quality. In your system it's worth a try!

markah posted:

Latest update - the NAP300 power supply is still humming at the dealers, they even tried fitting a felt pad at the transformer but no improvement. They will be in touch with Naim on Tuesday to see what they say. 

In my experience, hum seems to vary between Naim components and may even vary between different serial numbers of the same component for all I know. I had a slight hum on a Supernait and Hicap, a horribly distracting hum on an XPS which you could hear at the other end of the room but no hum unless you press your ear close to the case on a Supercap and 300PS. All were/are sited in the same place on the same power supply extension! I can't explain why the boxes hummed to different degrees (doesn't relate to transformer size) so I'd suggest asking your dealer if they have another NAP300 you can try. At least that would rule out that particular unit and its transformer...

markah posted:
Chrissw19 posted:

Hi Markah, you have a great system! I suffered from a randomly humming Hicap DR and similar on the 300PS but less frequently. It was quite annoying so I've bought an Isol-8 DC blocker (high current version) on an auction site just to see if it was going to work and it did, the humming is completely gone! The hicap was also suffering from a constant very low level hum that has disappeared. 

That sounds promising - I see they do an "Axis" range for DC-blocking, was it something from that?

The one I got is the Substation axis which is rated for larger systems. I checked with the designer if it was suitable and he said that was the one used by owners of larger Naim systems. Luckily there was an ex display one available on an auction site.

 

I've posted on this subject before.  (try a forum search)    Bottom line is you need to determine if the hum is constant or variable.   If the hum is constant & unchanging it means you probably (might) have a naturally noisy transformer - & all transformers make a noise to some extent, even the so called silent ones.  If the hum tone and/or volume changes for short periods or at different times of the day,  then you might (might) have asymmetrical waveform distortion (DC).  

It has been a while but I'm relieved and delighted to say my system is up and running again, after about 8 months without (for various reasons - it has been tough!). The main culprit (300 PS) was returned to Naim by my dealer and has just come back with a new transformer fitted. Although not silent, not that I ever expected it to be, the hum is virtually inaudible now and certainly not distracting as it was before. Such a relief that no further action is needed other than just sitting back and enjoying the music - which is exactly what I'm now doing!

Thanks to all who posted with advice, I certainly learnt a lot about mains supplies and transformer hum along this path.

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