Mains Conditioner

It may* kill the hum if the hum is caused by asymmetry in the mains waveform.  It may also kill all the excitement in the music leaving it bland, dull and flat.

There's only one way to know - try one.  Some mains conditioners are OK, most are not; this one may or may not be one of the exceptions - I don't know in this particular case.

If your mains is OK and you just have an inherently noisy transformer, then it'll still hum.

Yes indeed!-- I'd luv to hear the Pro's and Cons in this discussion--- the PP 2000i above is a Regenerator so hallowed by the esteemed Romy the Cat!

D41

Interesting review of the PP2000 in HFN this month. As usual, it doesn't work well with Naim but works well with some other kit. 

Huge posted:

It may* kill the hum if the hum is caused by asymmetry in the mains waveform.  It may also kill all the excitement in the music leaving it bland, dull and flat.

There's only one way to know - try one.  Some mains conditioners are OK, most are not; this one may or may not be one of the exceptions - I don't know in this particular case.

If your mains is OK and you just have an inherently noisy transformer, then it'll still hum.

james n posted:

Interesting review of the PP2000 in HFN this month. As usual, it doesn't work well with Naim but works well with some other kit. 

Hi Guys,

I don’t think that is the case re the hum adjustment comment. It doesn't change the dynamics at all, it just corrects a current

imbalance that causes asymmetric current flow that makes transformers hum.

There are other causes of hum - such as DC offset (audiophiles sometimes call it DC in AC), high harmonic distortion and some EMI noise - none of which exist in the PurePower AC anyway.

I do agree with the comment from various reports and listening session I’ve had—some "hum busting" circuits, including the one from PS Audio do cause loss of dynamics -

I know Naim and its true believers are, as one and all about their power supply, idiosyncratic. But the fact is, the DC bus voltage regulation is not really a full solution to utility AC issues since it

doesn't really isolate the amplifier from utility problems. Otherwise users wouldn't be playing with power cords and other power conditioners-ha!

What the PurePower for instance as reviewed  in HFN appears to do is give 100% isolation.

I sometimes wonder whether fellow Naim owners report changes in sound from hour to hour and day to day

- i.e. that midnight Saturday perfect sound that can't be heard on Tuesday dinner time?

Incidentally reading the review, the HiFi News reviewer reported that with the PurePower his Naim NAP300 “refined the sound quality” but “softened” it. Since the reviewer had the PurePower output set to 230

volts, vs the mains 240 it is possible he heard the difference in voltage as a “softer” sound – which is consistent with reduced voltage effects. Hmmm.

Good Listening!

D41

Hi D41,

Ironically I did have variable mains induced hum in my system, but I designed and built a custom  mains DC filter to fix the problem (i.e a high power rated high pass filter).  This gave the system a much more consistent dynamic characteristic.  Compared to performance without the filter, against the very best times without the filter, there is maybe a tiny loss of dynamics; against the worst times without the filter, it actually improves the dynamics; on average there's little change or perhaps a small improvement.

Setting the output level of the Pure Power to 230V is going to have no effect compared to British mains supply (as per the HiFi News test) as British mains is 230V not 240V!

am going to try doing some tests on our AC test rig this weekend on the 250DR -- see what makes it hum and grumble

Hi Jon,

I really look forward to the conclusions from some real, properly controlled tests - that will be most enlightening.

Great that you're prepared to stand the expense involved to setup for these.  Thanks.

well, thats what having a UKAS IEC17025 lab means...

And that rig would have easily bought a new 552. And... and.... and... 

Sigh

True Jon, true but it reaches parts that even a 552 cannot reach...

jon honeyball posted:

am going to try doing some tests on our AC test rig this weekend on the 250DR -- see what makes it hum and grumble

 

Jon, I look forward to your summary that I hope you post here. The DC offset here causes the my 250 high efficiency Toroidal transformer to saturate and buzz, and I am not convinced when buzzing that SQ is not affected.. although could be due to other things... so if you can look at that in a controlled way it would be interesting too. Certainly looking on a scope at the output of a DC offset saturated Toroidal transformer does not look at all healthy.

HIw much dc?

Foot tapper posted:

Greekspec,
The reason that you hear no transformer hum is that you are fortunate to live in California, which, is where new things come from.  The electricity is still fresh out of the ground, full of energy, youth, vigour and is well behaved when you receive it.  The UK is at least 5 years behind California in most things, so by the time it reaches us, the electricity is a bit tired, irritable and grouchy.  It is therefore far more likely to cause trouble for any appliance that it runs through.  Its mischief manifests itself as humming in large toroidal transformers.

To counteract this syndrome, I have installed a balanced power supply, which isolates the Naim power supplies from the tired, irritable electricity in the UK mains.  It has worked a treat.   However, this BPS has been working now for almost 2 years.  In another 3 years, I will need to drain the isolated supply circuit and refill it with fresh electricity to keep it in tip top, hum-free condition.

You are indeed fortunate to live in California.  FT

Foot Tapper, please tell me, you're not suffering from those humming blues!

I was hoping the Airlink isolated transformer done the trick.

At first, I thought it was just me, recently tuned in on Amp Characteristics, I think.

 Asked the question: 

Was the humming less apparent, with the DR amps?

You guy's are confirming MM, and others, no relationship, basically depends on the Grid.

 Can't wait to get your results, Thanks!

I guess it's not easy being in the Hi Fi Business, trying to satisfy your customer base!

Transformic Hum and External XO's

Allante93!

Hi Allante93!

No transformer hum blues here any more, I'm delighted to say.  

For details of the BPS installation, the impact of changing from 242V to 230V on the Naim system etc., search for a thread called "Suffering from those transformer hum blues?".  My impressions are all included on that thread.

Happy listening!  FT

jon honeyball posted:

HIw much dc?

i wouldn't put more than 1 volt - at least initially - bit would be interesting to hear the effects in a controlled way

Simon-in-Suffolk posted:

jon honeyball posted:

HIw much dc?

i wouldn't put more than 1 volt - at least initially - bit would be interesting to hear the effects in a controlled way

     whoa  !!!  I would not go that far.   I would start at something around 100mA DC,     You will probably find you'll get all you need at that level,  but I don't see any need to go more than 200mA DC.   

Nick from Suffolk posted:

Isn't the cross-channel link a DC link? So there is no cross-contamination of British and French electrons?

Indeed it is as is the case with most underwater transmission lines as the losses due to capacitance that you would otherwise have if you used alternating current are smaller..

Mike-B posted:

Simon-in-Suffolk posted:

jon honeyball posted:

HIw much dc?

i wouldn't put more than 1 volt - at least initially - bit would be interesting to hear the effects in a controlled way

     whoa  !!!  I would not go that far.   I would start at something around 100mA DC,     You will probably find you'll get all you need at that level,  but I don't see any need to go more than 200mA DC.   

 

Mike I think we are talking voltage not current....... 

A 0.5% DC offset (i.e. 1 VDC on 220VAC ) would seem a worthwhile amount - and should put more efficient Toroidals into saturation such as used by Naim - so they buzz

    Jon asked how much DC.   In my testing of transformers many moons ago we applied normal working voltage to the primary & regulated its waveform change & measured "DC" offset in mAmps.     

indeed so I said i would not put above 1volt of (of DC bias) on the mains - the current flow will depend of course on the efficiency of the transformer - the more efficient the lower the resistance and so saturation will occur at lower voltages. (fixing a current on higher resistance cores could cause quite high VDC offsets). So a step set of tests starting at  0.05 vdc to no more than 1 vdc ins step of .05vdc would be interesting. On a large transformer such as on the NAP 250, 300 etc I would expect the transformers to start buzzing at around 0.2vdc if not before  (I guess they have a resistance of around 2 ohms or so) and the smaller transformers perhaps not buzzing until nearly at 1 vdc and would typically have a higher resistance. I understand it is quite normal for households to have at least 0.05 vdc (50mV) of DC on the mains.

Shall we see what Jon returns with??

im still finding my way around the generator -- and given the scale of whats inside, i am being suitably cautious in my fiddling :-)

indeed - very sensible - I would certainly experiment on some cheap little device at first 

Am fiddling with a CB NAP140 that JV lent me some 29 years ago when i was working on a project for him. Technically its still Naim's. One issue is getting the DUT away from the generator, which has significant fan cooling as you can image.