This subject seems to come up very often here, so having the issue myself, and after a lot of reading, I thought it might be useful to have a simplified starting place to visit for these issues, bringing as many of the different causes mentioned in this Forum together. There are many more detailed items on this forum that you can then lookup specific areas.
Here we are referring to Hum/Buzz from the Naim PSU/Amp units themselves, and NOT Hum through the speaker (which could be more related to a grounding or cable issue).
Will resolving the transformer Hum/Buzz in the unit help SQ? Well possibly, or possibly not, or it can also drop. More likely the SQ will be improved by removing what external influences were causing the Hum/Buzz.
Important: This post is written from a UK prospective, but the basic ideas will be global.
DISCLAIMER: Where appropriate ensure you use a qualified person to carry out any checks that require their expertise, and you abide by any local Codes and Regulations.
1) Naim PSU/Amps will Hum/Buzz
It is very common that Naim PSU/Amps will Hum/Buzz to a certain degree, and this is quite normal, so one option is to ignore it. It becomes a problem if it is so loud that it becomes annoying, in which case investigate the areas below.
2) DC Offset
This is where a DC current is over-layed on the AC current. Likely candidates for causing these are other electrical heating appliances such as electric fires, cookers, swimming pools, fridges, hairdryers, curling tongs, electric blankets, etc
The problem can be worse at certain times of the day, and possibly quietest late at night.
Unfortunately I haven’t seen any good methods to measure this value, other than getting in an electronics expert with an oscilloscope. So it’s a matter of testing by elimination.
Solar Panels: If you have these, temporarily turn them off, to help (or not) eliminate the Solar Inverter.
Is the issue on any particular circuit: First shutdown any Computer Desktops, and power off other devices in the house.
Assuming you still have the issue, power off all circuits (including lighting circuits, immersion, etc) except the one you have your HiFi plugged into. If it resolves, then turn those circuits on one at a time to find the offending circuit.
To eliminate your HiFi circuit, use an extension lead from a different Main circuit (e.g. upstairs) and plug in your HiFi. Then power off all circuits except the extension lead one.
If you locate an offending circuit, then physically unplug the other appliances on that circuit to see if any appliance is causing the issue. If that doesn’t identify any offending electrical appliances, consider calling an electrician to test the circuit.
There is also a possibility of the issue being from another building, such as a local factory. Recheck at night when factories may be closed
How To Fix:
If the above testing doesn’t find any specific appliance causing the issue, then there are some other options.
The best option which is recommended by Naim, is to have a Dedicate Circuit for your HiFi - See details later
Other options that have been known to resolve Hum issues are Mains Blocks/Main Conditioner/Balanced Power Supply that are designed to filter out DC Offset. Also see:
3) Over Voltage
For the UK, the supply to your house should be 230V +10% -6%. That means a maximum high of 253V.
If you are suitably qualified/competent, use a multimeter to check your house Voltage at several times throughout the day, or when the hum/buzz is at its worse. Typically the Voltage will be higher when other houses are least using power, and lower when the load is higher.
If you do have Solar Panels, then check your Solar App as it is likely to already measure the AC Voltage.
If you have Solar power, then disconnect it temporarily to help eliminate the Solar panel Inverter as being the cause.
How To Fix:
Your Electricity Supplier must supply electricity within the tolerance, as outside these value may cause damage to the appliances. So if you are in the UK getting Voltages >=253V, then log a call with them. In my case, they came out within 3 hours, and adjusted the tapping on the local substation, and brought the average from 255V to 245V, and resulted in a quieter HiCap. Full details at:
If you are getting high values but within tolerance, then again first try your electricity supplier. Be aware that they may not adjust it any further, as they have to ensure that all houses on that circuit are within tolerance, so if you are at the substation end, then you will have a higher voltage than the furthest property, so it’s a balancing act. What they may do is put an extra meter next to your meter that records your mains supply details over a week, and will then make a decision at the end of that. In fact that’s what they did on my case as I want to get a lower average than 255V to reduce Hum/Buzz further.
If all else fails, then you can consider:
. Active regenerating power conditioner (creates a perfect AC Sine wave)
. Advanced Balanced Power Supply solution (some of these have different input to output settings, e.g. 250->230 or 240->230)
4) Problem actually with the Naim unit
If having eliminated most of the above items, you could also investigate whether there is an actual issue with your PSU/Amp.
The following is best check by someone qualified in electronics, but there are a couple of areas they might check:
Possible transformer seating issue. E.g. if device has been in transit. Consider just loosening the screws, and re-tighten them
Possible transformer foam pad seating issue. Has the foam pad disintegrated over time. See discussion
5) Physically move the PSU/Amp
Most people wont be able to do this, but it has been mentioned as a possible workaround if the physics of your room layout allows it. You will then run the cables through the wall. You could also enclose the whole HiFi Rack inside a purposed built cupboard, ensuring isolation between the two, and air can flow freely.
Other alternative might be to move the PSU/Amp to a different place in your rack, furthest away from your ears.
“Transformer hum is not transmitted through the speakers and has no effect on the performance of the system; however, a separate dedicated mains radial circuit may reduce it. Such a circuit (in UK, ideally with a 30 or 45 Amp rating) will also generally improve system performance.” This was mentioned at the thread below and says it comes from Naim:
This has been mentioned many times on this forum for Hum/Buzz resolution and particularly SQ improvement, although it wont fix DC Offset or Over Voltage issues coming from the Mains Supply.
The solution here is to add a dedicated HiFi Consumer Unit and creating a separate radial circuit. In the UK you would ideally be using 10mm2 core cable (and possibly shielded), specifically with a good earth of 10mm2 also, but does assume the end socket is designed to take such a thick cable. Remember good earthing is needed for dissipation of static charges, EMI and RFI signals and interference. This solution can give a remarkable SQ boost per cost.
The following thread includes a great circuit diagram:
Also search the forum for “radial circuit”, plus check with your local Naim dealer for advice more fitting for your country.
New sockets/refit sockets:
In fact, there is no mention of this resolving any Hum/Buzz issues, but I think the following discussion which is around replacing old sockets and/or refitting all sockets on the ring, may help here, and if it doesn’t, it is a cheap thing to try, and may improve SQ.
Also try reinserting all plugs in the house a couple of times to ensure good connections (as you would do for Naim interconnects).
Probably the “Bees knees”, as these take any old quality mains, and spit out a nice clean Sine Wave AC current. Should stop Mains Hum, and improve SQ. Problem is they are expensive at ~£10k.
Mains Blocks/Balanced Power Supplies (BPS)
A bit of a catch all section. These are known to resolve/improve dirty mains Issues, such as DC Offset and Over Voltage. They have also be known to improve SQ BUT have also been known to drop SQ, so Naim do not recommend these and therefore don’t jump in feet first without consideration.
You ideally don’t want too much mains filtering, as this can negatively effect SQ. Best to look at a solution that solves your particular problem.
TRY BEFORE YOU BUY if possible. Your local dealer may be able to help you.
BPS: Although these have great success in resolving/improving Hum/Buzz issues, it was noted in a couple of case that the BPS devices itself hummed, and therefore the hum was just moved to a different device, albeit quieter.
If you have a dedicated HiFi radial circuit, then you might consider placing a BPS next to the dedicated Consumer Unit, rather than next to your HiFi.
It’s not my place to recommend any particular solution here, but the Forum regularly mentions devices from Airlink Transformers, Isotek, MusicWorks and ISOL-8 PowerLine Axis. Just search on these names in the Forum and you ensure you read all the threads to make your own mind up.
Also have a look at:
Please “Like” this article if any of the above has helped you, or please add other fixes below?