Speaker hiss

Hum through the speakers is something all together different than white noise, hiss, I would be concerned if hum was audible through the speakers. 

Hum, which is normally mains frequency, ideally should not be audible at all, though it is not uncommon - but in practical terms it is on no consequence if it can’t be heard from the listening position. It can arise anywehere from the first analogue signal (cartridge or DAC output stage) to the power amp final amplification stage, via interconnectes or electronics. Hiss, on the other hand, is inevitable, though there again it is of no consequence if it can’t be heard from the listening position.  The sound level of hiss and hum are directly proportional to speaker sensitivity - so highly efficient horn speakers are far more demanding of low hiss and hum than the majority of speakers.

There was a similar thread to this not long ago called Audiophile Paranoia, worth a read.

Consciousmess posted:

Obviously when one puts one’s ear by a tweeter with no music playing, it is expected that there is still white noise coming out - in every case, regardless as to how ultimate the system and speakers are.

That being said, assuming the ‘perfect’ setup, is this the ONLY sound one might expect? No electronic hum albeit small? I ask as does the electronic hum suggest improper installation somewhere?

(You may jest at this question, but reading the forum and activities some do, justifies any question of this sort!)

 

Badlands and Innocent Bystander are correct.  White noise hiss is normal; low frequeny hum is not. At what volume setting is it apparent?  Only volume levels you would never use?  On the CD input on my Naim amp i cannot imagine ever going further than about half past ten, a bit more for vinyl.  If it's only with the volume at full or nearly full you might choose to live with it but at normal volume settings it would annoy me.  I suggest you search the forum for 'earth loop'.  Do you have AV equipment connected on a different set of mains sockets than your Hi-fi?  If so experiment using a long extension lead.  If the hum goes away there are then various more permanent solutions.

Going off on a slight tangent, on the CD555 (and probably some other Naim sources) you can connect via RCA, DIN or even both (not sure in what situation you would do tnis).  I'm probably in the minirity who use RCA.  If I tell the CD555 I'm connected using DIN or both RCA and DIN i get a hum.  Before anybody starts thinking 'so what, who cares, why would you ever want to do that?' every time the equipment is deliberately powered down or after a power cut I get a hum.  The CD555 seems to correctly recognise it is connected via RCA but i actuslly have to cycle through the options and reassign it to RCA before the hum goes away.  It takes about 10 seconds but caused huge frustration diagnosing the problem.  I'm not sure if it's a fault or more of an idiosyncracy.

Of course, hiss and hum that you get when playing but not when not is very likely recorded with the music -  hiss is particularly noticeable with some analog recordings, presumably tape hiss from the original mastertape, but some recordings have recorded a hum from somewhere. I say very likely recorded with the music, but there can be other causes - I recall many years ago investigating a friend’s hum problem, finding it was the cartridge picking up the magnetic field of the motor or transformer (I don’t recall which) increasing as the pickup traversed the platter, with almost nothing when arm was in rest position.

Bryce Curdy posted:

  I'm probably in the minirity who use RCA.  

 

Me too sir! I actually prefer the sound when compared to the DIN alternative.

I have hum through the speakers and it's proportional to the loudness of the case hum of the 250 that is connected. The CB250 is near silent and there is a very tiny bit of hum if you put your ear right next to the tweeter. The other olive 250 is appalling and you can hear the speaker hum from much further away and the case hum from the other side of the room. Loudness doesn't change with volume control or whether the pre is muted or not.

No phono device is attached but there are phono boards inside the pre. Is there a way of I suppose capping them off? Would that make any difference and is it worth capping off all unused inputs and record outputs?

srichards posted:

I have hum through the speakers and it's proportional to the loudness of the case hum of the 250 that is connected. The CB250 is near silent and there is a very tiny bit of hum if you put your ear right next to the tweeter. The other olive 250 is appalling and you can hear the speaker hum from much further away and the case hum from the other side of the room. Loudness doesn't change with volume control or whether the pre is muted or not.

No phono device is attached but there are phono boards inside the pre. Is there a way of I suppose capping them off? Would that make any difference and is it worth capping off all unused inputs and record outputs?

Something seems odd here. Firstly, you refer to hearing hum from the tweeter. Hum is at bass frequencies, usually mains frequency, and would be from the woofer. Please clarify. (At the risk of stating the obvious, hum sounds a bit like a man sounding a low “mmmmmmmmmm”. Hiss on the other hand sounds like a high “ssssssssssssssss”). 

If hum from the speaker is not proportional to volume then it is from either the power amp or the pre-power interconnect, or connections  If the olive making the hum is happens just swapping at with the CB with all else identical, it suggests that there could be a fault with the olive.

Sorry I will clarify   There is hiss from tweeters . The hummmmm is from mid bass driver area.  The olive has always been like this. It's been off to naim for a service and came back just the same so I ignored it but after turning it off during the bad weather and turning it back on it's suddenly apparent just how loud it is. It's also putting out a wall of hissssss that is twice as loud as the CB. I too think the Olive 250 is a duffer

CB250 is a lot quieter in all regards. The 52PS that naim serviced also hums and always has. I expected servicing to fix these sorts of issues but it seems it doesn't.

Thanks for clarification.

Hum direct from the amp, as opposed to through the speakers (even if they sound the same) is from the transformer. Whilst a faulty transformer or one with a loose mounting could cause hum, it does not necessarily indicate a fault with the unit(s), but possibly a problem with the mains supply, as that type of transformer can be susceptible to mains imperfections, notably DC offset, and the degree of hum can vary between individual transformers. If the hum sometimes suddenly becomes louder or softer then it is almost certainly this, though an absence of such changes doesn’t mean it isn’t. There have been various threads discussing this and possible solutions.

Try turning everything else in the house off. Does the hum stop? If so, turn things on one at a time. This should show what is causing the mains borne interference. 

My amp / power supply hum quite noticeably...in true naim fashion

I installed a simple DC blocker and stopped it completely...but also managed to get the feeling something had been taken away.. thought I could not put my finger on what

Anyway ... removed the blocker again and I just live with the hum now...it's a naim thing.

My two power supplies are completely silent. 

Japtimscarlet posted:

I installed a simple DC blocker and stopped it completely...but also managed to get the feeling something had been taken away.. thought I could not put my finger on what

What DC blocker was it ???    I'm interested as I use my own design & if anything (ever-so-slightly) it enhances the SQ.  It does not stop what I have concluded is naturally humming Naim traffo's,   it does stop variations in hum tone & volume & its now only a low volume hum audible only in a completely quiet room.      

It's on a filtered socket so any crud from other things should be blocked theoretically. It makes no difference on what is turned off. It hums regardless. It's hummed the same in two houses with different speakers and different all sorts. It's why I sent it off for service the first time.

The filtered socket is unlikely to remove DC offset, which is the usual cause of transformer hum.

incidentally, when in an earlier post I suggested there may be a fault with the olive one, I was specifically referring to loud hum through the speakers, not direct from the unit.

OK,  if its a filtered socket I doubt its able to block DC,  the parts needed for a DC blocker are too big to fit into a socket.  I suspect the filter might be C&D mode "noise" filter,  if so it will have X&Y shunt capacitors & these are reputed to kill some aspect of SQ.      

indeed  if there is a bad imbalance on the mains with a resultant DC offset then it is quite possible that SQ will be impacted. The transformer will be saturating - which is the buzzing you hear - and when it saturates then some horrible wave forms are going to be produced on the secondary winding which most power-supplies will have to work very hard at to completely clear. Here is an example of current spikes (bottom row) caused by a saturating transformer with a sine voltage across its primary (top row). In practice the spikes may well have harmonic noise as well. Here a so called linear power supply can be actually quite electrically noisy - more so potentially than a quality SMPS with the same conditions, though a saving grace - is that small transformers are usually less efficient and so are less inclined to saturate. Its the larger more efficient toroidal transformers which are most sensitive to this.

There is a hum through the speakers with the other one. It's a lot quieter though. Dirty mains is a fact of life these days so there should be a naim friendly solution out there by now.

Does the DR upgrade do anything to stop hum? That's another option.

srichards posted:

There is a hum through the speakers with the other one. It's a lot quieter though. Dirty mains is a fact of life these days so there should be a naim friendly solution out there by now.

Does the DR upgrade do anything to stop hum? That's another option.

 

I use an Isol-8 Powerline Axis -- a mains block with DC blocker, but no mains conditioning. It wasn't cheap but cured the transformer hum blues... 

Same experience here - so positive that I invested in two. They're very well made too and I've not noticed any negative effect on SQ.

This is probably a daft question but the 6 power sockets on the axis. Are they square 13 pin style ones or iec? All of the photos show them with the covers over the sockets.

Sprung covers over UK sockets - although there may of course be EU and US versions

Timo posted:

srichards posted:

There is a hum through the speakers with the other one. It's a lot quieter though. Dirty mains is a fact of life these days so there should be a naim friendly solution out there by now.

Does the DR upgrade do anything to stop hum? That's another option.

 

I use an Isol-8 Powerline Axis -- a mains block with DC blocker, but no mains conditioning. It wasn't cheap but cured the transformer hum blues... 

P.S. A good dealer will have a demo unit. I "tested" the power block for about a week to be sure that the Isol-8 was fixing my transformer hum -- and wasn't compromising sound quality. After that week I happily placed the order. 

And good to hear from @Ravenswood10 that the Isol-8 doesn't damage sound quality when climbing up the ladder -- reassuring! 

and  for me having the hum banished made the who listeining experience that much more enjoyable. Of course if you have a clean mains supply so much the better but I live in a rural area with farms around and goodness knows what they put into the mains. Of course the best option is to borrow one from a willing dealer and try for yourself.