552 volume control/balance problem?

I think this is a fairly common problem with Naim volume pots; it does not happen on the resister ladder type volume control on my 112x. If it bothers you too much I could be persuaded to do a swap!

Thanks Morton for your kind offer of swapping .  Bofore I give your offer any further thought, I'd like to see if any 552 users here are facing this same problem that I'm having.  

I also heard from other HiFi enthusiasts that the kind of volume pot  which Naim is using on 552 can result in this "unbalanced" sound level when the sound level is low, but I guess Naim might have used a potentiometer or similar appartus to check it before the units leave Salisbury?  Any users of 552 or other Naim pre-amps using the same volume pots here may share your experience?  Cheers!  

I think is simply a tolerance thing between the two channel volume potentiometers. (They track each other logarithmically, and so any differences in the low volume settings are magnified) I have never experienced this in a noticeable way with Naim, but did notice it once with an electronic volume control on a non Naim preamp.. But reading on the forum including your post others have. If it bothers you ask your dealer to address. If sufficiently within tolerance it might cost you to have the pot swapped out... But there is no point in having a Naim 552 or any Naim for that matter you can't enjoy..

Simon

Simon HK You're right I also noticed a stronger left side to the right or, alternatively, brighter on the left side

A slight imbalance during the first few degrees or so of pot travel can be normal - very high sensitivity speakers can often magnify the issue, whereas it's pretty much un-noticeable on more average sensitivity speakers used with regular source outputs of up to 2V. If a source exceeds 2V though, again there can be an apparent problem. The pot used in the NAC552 is the ALPS Blue - because, according to Naim, it sounded better than all the others that were tried instead during development.  The possibility of imbalance at the very beginning of the track on even the best pots is well known, but I suppose is accepted for the SQ on offer. Naim fit balance controls too, so it can always be balanced out if noticeable.  To ameliorate this effect the 552 uses a specially selected example of the pot where any imbalance is minimised and of a small to imperceptible degree.   While it may well be possible to swap out the Pot board on this NAC552, there's probably no guarantee that it will be any better - they are already specially selected to within a certain threshold. 

Simon HK, small consolation but similar issue with my new 252, drove me completely insane in the first week of installation. I'm not a loud listener and at lower volume levels I noticed a slightly brighter right channel , but now getting familar with a higher volume level where left and right even out. Changed cables, swapped speakers and used the mono button to determine it was the volume control (balance control didn't seem to solve the problem). But one thing I did notice that had a big impact was how albums are mixed, highlighted when you get a 2 for 1 (2 albums on 1 CD - same band but with different studios/producers/engineers etc). On one album I was hearing the hi-hat/cymbals/tamborine mixed clearly on one side then on the next track (second album on the CD) all the top end instruments snapped to the centre or moved from left to right. In addition, getting used to a new listening experince with the 252/300 where the level of detail and placment of instruments is just amazing compared with my old Musical Fidelity system.

Our 552 had this on its volume pot. The factory fixed it no problem. The new pot is actually balanced in favour of the other channel now, but the difference is insignificant to us. The old pot sounded worse at low volumes and one channel disappeared some way before the other as the knob was wound down, so we didn't need to factor in the room. Some fiddling about with different inputs, DIN leads and RCA leads plus swapping the speaker cables was gone through and repeated a number of times before Naim got involved, Once they did it was plain sailing.

I totally agree with Richard.

Yes there can be a small imbalance at low volume (typically only below the '8 o'clock' position, but it can become significant in the first few degrees of action - typically just below the '7 o'clock' position).  This is a mathematical problem  inherent in the way Log law potentiometers are made - it can't be completely eliminated.  The Alps 'Blue' pot is a high quality item and the error is actually smaller with these than many other types of pot.

My experiments also indicated that Alps 'Blue' potentiometers are the best sounding.

A case could be argued here for a refresh of pre amps to all feature the volume system of the Statement and 272 derivative.

ermm these issues are just almost as likely to occur with electronic volume controls as with traditional. The issue is the tracking of the low level resistance changes between channels at the very low volume settings with respect to volume control rotation arc distance.

One effective remedy would be to have input level matching, such that tracking errors were not noticeable, and that 5 o clock meant full listening volume... as opposed to overload... but I guess other than the Statement which I believe has this ( though could be wrong) the added complexity would detract from the sonic performance.

Simon

Didn't think the statement had a volume pot as such , more a bank of relay resistors,  the 272 having a simplified version.

Yes, my non Naim pre-amp had an electronic volume control, and that had a large number of low noise precision resistors effectively set up as a graduated logarithmic potential divider I believe, but that had noticeable imbalances between left and right at very low levels.

I thought the Statment had preamp channel input gain adjusters, but I could be wrong..

The Statement and 272 (and SU) may be using a discrete resistor ladder networks for volume control; and, with this, when using precision resistors, the balance tracking can be kept below human perception levels (but with some designs that's not always the case.

Using active gain control has exactly the same problems as using passive attenuators, the accuracy of L/R gain ratio is directly analogous to L/R attenuation ratio!

However the problem with discrete resistor ladder networks (in attenuation or gain control mode) is just that - it's difficult to maintain audio quality through networks with so many discrete resistors.  There have been various suggestion to ameliorate this problem.  I don't know if Naim have used one of the existing suggestions, or have developed a novel approach.

Huge, indeed, I  assume it's the latter... Or/and perhaps used some sort of LSI device where the accuracy can be laser etched at manufacture..for accuracy and stability.. There are certainly some neat ideas out there, as some similar challenges I suspect are experienced with ladder DACs and I know TI have developed some interesting solutions..

Talking about LSI (or even small scale integration), CMOS transmission gates have interesting potential.  If the MOSFETS were formed on a single die, their characteristics can be exceptionally well matched and by using one pair as a reference to linearise the transmission through the signal pair, it may be possible to produce a system with no mechanical switches.  (Perhaps using a microcontroller to generate the logarithmic response required, instead of the tradition method of using the forward V/i response of a diode.)

I don't actually think this is how it works, but it's an interesting possibility for speculation! 

Wouldn't say no to something with the range and feel of the above providing there was no compromise in sound quality. Since the S1 used this kind of arrangement I don't think a compromise would be inevitably inherent.

Thanks for all the helpful replies and enlightenment above guys.  I'll arrange the dealer here to come and have a look and see if anything could be done to my beloved 552 to, at least, minimise the issue. I'm not saying this issue really gets into my way of enjoying my 552. The combo is immensely enjoyable of course, but having a balanced level from the two channels would be so much nicer especially that my speakers are of high sensitivity and I rarely need to turn the volume knob beyond the 9 o'clock position.  Unfortunately, the two channels only get near to balance when the volume knob reaches the 12 o'clock position

12 o'clock does seem a bit extreme.

Presumably you have swapped the speaker leads over to confirm the problem is the amp/preamp and not the speakers or connections?

Oh yes wanderer, speakers have no problem as there's no such issue with my other set of pre/power amps. With 552/500, I swapped SL speakers cables, swapped the stock din to xlr cables, tried different inputs on the 552, all the same. Must be an issue with the 552, albeit not a serious one, as I've made it clear in my above post.  And, 12 o'clock it is, for sure, for otherwise I wouldn't have posted this thread to look for you guys' views, and wouldn't be troubling the local dealer who are a bunch of jolly nice guys. 

Most of the Naim amps + almost every other high quality pre/ integrated amp uses the Blue ALPS volume pot and most can sympathise with your situation . 

It is common or used to be - hence the use of input attenuators to bring sensitivity down. This day and age we should expect more and other marques can provide more...

Oh dear, this is worse than I thought, so unfortunately, I must formally withdraw my offer of a swap!

Seriously though, I could not live with that no matter how good the sound; I’m sure Naim will sort this for you.

Indeed Morton, and I trust the dealer here (in HKG) will sort that out for me, provided that could be sorted out , that is.  

Same here but it did irritate the heck out of me, particularly at low volumes and when increasing from a low volume or decreasing from a high volume, when the balance control would also need readjusting. 

Well Zeny, I wouldn't go so far as saying it's scary, just an issue that I need to sort out.  Also perhaps an additional price (in addition to the rather high price tag of the 552/500 combo) that we need to pay for the rather engaging and unique Naim sound.