555ps hums

so does mine, (and also the supercap for my superline, this one started recently).

but when music is playing i dont hear the hum, so i am not really too bothered.

enjoy

ken

me too;but the noise it self ,is just a bit loud.any idea to solve the problem ?

tks

i am afraid not, other than purely empirical and trial and error ideas like changing the location of the unit in the rack.

enjoy

ken

I think some others on the forum have suggested that the hum from the PSU transformers becomes more pronounced when they are having to work harder to keep out dirt on the mains which can be worse at certain times of the day.  I've got my system on a dedicated rings-main which isolates it from the noise created by other electrical appliances in the house and my PSUs seem mostly very quiet.  So a separate rings-main or spur might help but I know it's not a quick or straightforward job.

MDS

I find it's worse in the afternoon when it does happen to my Supercap or the 300 PSU. Hard to tell which one it is as they're both on the brawn side of the rack stack. I'd have thought Powerlines might have helped clean up whatever causes the humming though.

Giovanni,

Ask your dealer if you can try another one to see if you still have the same problems.

I remember when I bought my system and weeks before ordering when I borrowed the same system for home demo, that the 300PS was quite bad. My dealer said don't worry we can just send it back and try another one if this happens with the one that you buy. I guess some toroids are more sensitive than others.

I have a dedicated spur for my system and my toroids still hum. A different power-supply unit can hum at different times and days depending on the frequency of the mains-borne distortion.

It's an old problem. Julian Vereker's succinct advice to someone with a humming 250 at a Hi-Fi show many years ago was "If it bothers you, put it in a cupboard."

Sadly, mains quality will probably get worse. The holy grail would seem to be a practical and affordable mains conditioning device which doesn't suck the life out of the music. Naim are certainly cognisant of the problem and possible solutions.

John.

i have 10mm sq radial feeding the system sockets -- and i thought that this would eliminate this hum ... did for a while, but it all came back. i now accept as 'comes with the territory', but i did not know about this dealer exchange system when one buys a humming bird. sounds like good customer service to me.

enjoy

ken

other than 'put it in a cupboard', what other possible solutions do you know that naim recommend John?

The 'cupboard solution' is no real solution for me -- all my components are on fraim stacks...

enjoy

ken

Hi Ken,

There's a Fraim cupboard coming apparently.

Naim have obviously investigated the possible merits of mains conditioning devices, but are seemingly unable to recommend one which does not have a deleterious effect on the music.

I get the impression that it can possibly be done with enough money and something the size of a garden shed.

Tricky.

It seems that silent Switch Mode Power Supplies simply don't cut the sonic mustard as far as Naim are concerned - but hey - never say never.

Is your 300 back? If so, has audio nirvana been re-established.

John.

I have had varying degrees of transformer hum since getting a chrome bumper 250 back in the 1980s. And with 6xNAP135s this was sometimes quite loud. As suggested above isolating the offending equipment to an adjoining room/closet is one somewhat impractical but very effective fix. Sometimes all that is needed is to have the nut on the mounting transformer bolt slightly tightened. 

What I can say though is that the hum was absolutely eliminated with a balanced power transformer, which contrary to belief is merely the size of a wheelbarrow and not a garden shed. But it does weigh about as much as the shed does, and costs a shedload of money. The model I use now retails for circa $8,000 USD which is 2.5x what I paid for it years ago when the cost of copper was a fraction of what it is now. 

I doubt that any mains cable swap would have any effect-for that to happen the mains cable would through its LC properties block 50/60 Hz signal...which of course would dramatically lower the voltage received by the device under test, which then would not work at all. Having said that I have known of boutique mains cables that were 'tuned' that indeed shaved several volts off the mains going into the electronics. 

Fraim cupboard ! ha ha ...

'Something the size of a garden shed!' ah, so that the size of the xformer in the next series of products then?

no my 300 is not back yet, its just coming to 4 weeks that i was uoted as likely turnaround, so its probably any day now.

i am still runing wonky with James's Olive 250 on bass. Sounds quite good --- though i must admit that i am beginning to miss my 300 now. But i would rather have it fixed once and for all than rushed unnecessarily. And it would probably make sense if the 300 was delivered together with the 555PS which went to Naim round about the same time for DR-upgrade.

seems there are a few changes afoot in my system during the next few weeks... exciting, i guess...?

enjoy...

ken

Dunno.

All i an say is that sometimes the offending units do not hum at all -- so its intermittent (in my case). Sometimes the Supercap or 555PS can be silent for week, and for suddenly start humming like mad for the next few weeks.

Perhaps mains quality variation, or someone plugging in a noisy appliance in my neighbourhood? or...?

enjoy...

ken

Giovani, large torroidal transformers hum under no or light load because of DC on the mains. With DC pollution the hum tends to be a growl and will typically vary in intensity. You can use a DC blocker filter or a balanced transformer as discussed to remove the growl. Small transformerto don't tend to growl because they have higher impedances, and so more loss for rhe DC to be dissipated in.

DC appears with some types of loads or when there are loading differences across the phases from the substation.

Some large SMPS (like in plasma TVs) and inductive loads like hair dryers/vacuum cleaners  can create DC in the mains.

Simon

Simon, 

Very good info here. NOW I get why smaller xfmormers are more immune to this hum, while 552PS/XPS etc can hummmmmmm along unimpeded. And after all, there are some power supplies that use a resistor to pad down noise. 

no sure i completely understand. if the hum is caused by DC, then why does tightening the transformer mounts (apparently) seem to make a difference? this seems to suggest a mechanical issue?

and why does the humming seem to differ across samples of the same model, as reported above when folks have returned their units to dealer for xchange with quieter units??

seems there is more to this than perhaps just DC effects alone?? but of course, i may have misunderstood...

enjoy

ken

Despite their cost, Powerlines are not a cure-all.  They are totally passive; nothing in them can clean up a "dirty" source of power. 

As I understand it . . . the fact that we can hear a hum means that there is something that is physically creating it -- some element of the transformer is vibrating at the frequency we hear.  The origin may be unwanted artifacts in the electrical source, but the result is that their impact on the transformer creates a physical vibration which produces a hum that we hear.  It would well be possible to do something that'd stop the hum from being produced even though the transformer is still dealing with the problem.  Or one could try to remove the source of the problem -- the 'dirt' in the power.

Hi all,

With me it is only 552 that wants it's presence heard, intermitently. As I mentioned on a previous thread my new nearly top of the range Siemens dishwasher has proven to be an absolute nightmare.   

Only use when not intending to have a serious listening session. Have recently discovered that a house down the road on the same phase as me operates several commercial sewing machines and I think this is the cause of my transformer noise.

the main cause of hum is either positional or  of laminations vibration due to loose fitting. not dc content has most think. other transformers very near may increase hum..

Bart, Bill and Ken, indeed the hum related to DC is caused by the laminates responding to the peaks in the current flow at idle.

A well regulated transformer like a toroidal is finely balanced to ensure the full range of the magnetic hysterisis curve or range of magnetic  flux is used without going into saturation. With pure AC you have total blance so you have optimum swing of the magnetic flux. Therefore the current flowing through the transformer resembles a smoothed square wave ( transformer hysteresis is non linear).

However make the AC signal asymmetric by introducing a small DC offset, and for one half of the duty cycle the transformer will begin to saturate. This saturation creates small current spikes through the input windings of the transformer on each cycle in idle load state. These current  spikes grow with the earlier onset of saturation, ievmore DC offset. These spikes modulate the laminates, ie make them buzz proportionly to the DC present.

This happens at no load.

A transformer will also hum consistenly albeit generally more smoothly and more quietly with no DC, and under load will hum as the current increases. However the DC offset causes the noticeable varying hum at no load. Loose laminates will make a disprortionalely loud hum in all the sceriarios. 

Further to my earlier note on types of load that cause DC I forgot to mention the DC causing loads tend to be asymmetric, that is take more current in one half of the AC cycle compared to the other. One notorious cause are heaters with a diode in series to provide half power and full power..

Simon

I'd be starting to worry !  Hope you're ok Peter

My old olive kit used to hum a fair bit but when I went over to new black boxes this disappeared completely. For a while. Just recently it's made an unwelcome reappearance and this happened to coincide with my Supercap and 552PS both being DR'd. It may be a coincidence because the problem is worse at a certain time of the day.

I suspect someone around here has gotten a new bit of niosy electrical equipment. I'm out in the wilds of Suffolk so there's not much around about. I'll have to interrogate the neighbours. No problem with music playing of course. 

Simon, many thanks. You obviously know a lot more about this than i do -- i am still not clear why, for the same DC polluted mains, there (reportedly) seems to be sample variations on this humming issue. That is, one unit hums loudly, but when exchanged for another of the same model, the hum is reduced substantially. Is it something to do with tighness of lamnates that you mention above?

enjoy

ken