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Weird problem with Naim CDS

Discussion in 'audio' started by Johnny Blue, Nov 22, 2010.

  1. Johnny Blue

    Johnny Blue I made it to 'Member'!

    This is very odd…

    Just been listening to a CD (a 73 minute long compilation CD-R I’d just burnt) on my ageing Naim CDS, when, on the last track, the sound suddenly cut out, only to re-appear a few seconds later.

    At first I assumed it was just a bad burn, but then I noticed that the periods of silence were accompanied by the lit-up Naim logo going off (all the other LEDs on the display – the track/time indicator and the play button – stayed on).

    I skipped back to the previous track, all OK, then on to the last track, same thing; sound cuts out, Naim logo goes off. Playing around revealed that the initial point at which this happened (around 30 secs in) was pretty consistent, but after that pretty random in terms of when it occurred and its duration (mostly around 5 – 10 secs long).

    I also found that if I skipped to the previous track whilst it was in ‘off’ mode (i.e., no sound, Naim logo off) then there would be silence on that track, until after a few seconds it would come back and be OK, and continue playing normally until it got to the last track, when the problem would appear again.

    Tried a few other CD-Rs: no problem. Tried the fault-causing CD-R in another CD player: no problem.

    I was initially very concerned because I took this cutting-out as an indicator that my CDS was on its way out, but the few other CDs I’ve tried play perfectly.

    TBH, I wouldn’t have bothered about asking about this problem (putting it down to a dodgy CD-R burn) except for the weird thing with the Naim logo going off when the sound cuts out: what's the connection between these two things, yet it isn't affecting the other LEDs?

    Gentlemen, the floor is yours…
     
  2. dave

    dave Plywood King

    John,

    What happens when the original tracks used to create the CD-R are played (assuming the source disk was a commerical CD)?

    IIRC, one of the CDS-class players had the ability to go into protective mode if it sensed DC (or damn near it) being passed from a disk read. I believe this was to protect the amps and/or speakers vs anything else. I could be completely wrong about this however.

    regards,

    dave

    PS. An email to: info@naimaudio.com with specific model (CDS, CDS2, etc) and serial numbers for head unit and power supply should get you a definitive answer.
     
  3. Rasher

    Rasher Quadrophenia land

    I also have a CDS1.
    It is extremely fussy about copied discs and very often refuses to play them unless I burn them on an old version of Nero at no faster than 12x, and even then it's pretty hit & miss whether they will play to be honest. I still have a downloaded Flac, which I have paid good money for, and still can't get onto CD successfully. I can play it in the kitchen, car, living room, but not on my CDS1, and that's really annoying.
    I wouldn't panic about the player necessarily.

    Oldie also has a CDS1 and has the same problems, although his is a little more tolerant than mine, but not much.

    I just get 'Err', but it sounds as if yours at least is attempting to play it.
     
  4. wylton

    wylton Naim and Mana member

    The problem to which you refer is generally caused by DC offset which is present on the CD. The CDS is sensitive to DC offset and has a protection circuit which prevents DC from being passed through the amplifiers to the speakers (which would fry the voice coils). When offset is present, the circuit cuts in; this mutes the sound, and the logo will momentarily dim.

    I myself use a CDS and probably have 3 or 4 CD's which do not play properly. My solution is to copy these CD's to the NAS and play these via my PC.

    If the problem is due to DC offset then there is nothing wrong with your CDS, the behaviour is normally and as you say, these CD’s will play on other machines (which are not sensitive to DC offset).

    I should add that DC offset is generally caused by poor mastering, as it should be removed prior to the commercial release of the CD.
     
  5. wylton

    wylton Naim and Mana member

    I should also add that if you copy a CD which has DC offset present, then the DC offset will still be present on the copy.
     
  6. Johnny Blue

    Johnny Blue I made it to 'Member'!

    Fascinating stuff! I have never had a problem with my CDS not playing any kind of CD (i.e., either manufactured or CD-R) before, other than when the top hat puck has lost its grippiness through the neoprene O-rings flattening too much (a problem I have learnt to solve through PFM).

    This thing with the Naim logo going off (not just dimming, it went out completely) is entirely new to me: perhaps I've just been lucky? Thanks, Wylton, for the explanation and to Plywood Dave for the suggested explanation!

    Now, can anybody explain (in really simple terms) how DC offset can occur on a CD? I have heard of it before, but assumed it was limited to amplifiers...
     
  7. wylton

    wylton Naim and Mana member

    Normally an AC signal is referenced to zero (i.e. 0 volts), but when DC offset is present, Zero isn’t zero, it’s whatever value of DC is present. When the final mastering is done any DC present should be removed by using a high pass filter, but occasionally this isn’t done, hence there will be an element of DC present on the final disc. I have found that this most often occurs in electronic music where various electronic devices such as signal generators etc are used. For example I have a couple of Murcof CDs that don’t play properly, and I also had a Cathode CD which I eventually changed for an LP for the same reason. If you heard these albums, you could easily tell what I mean when I say that they are likely to have DC present if due care and attention isn’t paid at the mastering stage.

    In any case, DC offset is undesirable, because it has other unwanted effects on the audio signal such as reduced headroom etc.
     
  8. wylton

    wylton Naim and Mana member

    Incidentally, referring to the top-hat pucks, I abandoned these ages ago; I use one of the later types that have no rubber rings. I know that it’s not a Naim sanctioned mod, but I have found no disadvantages in using them.
     
  9. Johnny Blue

    Johnny Blue I made it to 'Member'!

    That would be it: it's some Trance/Electronica/Chill stuff I was preparing for a forthcoming party (not that anybody else will be interested in it: most of them'll be thinking that Disco is way too modern... ).

    Thanks for the information, Wylton.
     
  10. linnaudio

    linnaudio glad my Naim isnt really Linn

    ive played tons of trance/house on my CDS3 and never seen this problem although they have been originals
     
  11. wylton

    wylton Naim and Mana member

    Being originals has nothing to do with it, in any case this is about the CDS1 not the CDS3.
     
  12. linnaudio

    linnaudio glad my Naim isnt really Linn

    fair enough but someoen else states CDS class CDPs not just a CDS. Am presuming being a CDS3 it is a CDS class. Can this DC offset be induced in the coping stage by say a bad CDR for instance? I know absolutely nothing about this but was curious
     
  13. oldie

    oldie pfm Member

    Not the same problem ,but as some the remaining CDS1 owners have stuck their heads above the parapet I originally contacted Paul at Naim over the reluctance of my machine to play "some" burned cd's.he informed me that whilst not condoning the burning of cd's,the the problem was that the CDS1 was very sensitive to the depth of the laser burn and the faster the speed you burn at,shallower the burn and the more probable the player would reject it. Paul suggested a one to one speed for best results :rolleyes: I have since only burned at either 4 times or 8 times using Nero 7 for myself and Rasher on the VERY FEW times you understand that I have copied a cd :D So far that seems to have cured the problems.
    But what ever you do hang on to what imho was the best sounding CD player to come out of Salisbury.
    oldie
     
  14. Craig B

    Craig B Re:trophile

    John,

    You can remove the DC offset from the offending track, before burning it to CD-R, using Audacity which is freely available open source software.

    After opening the track in Audacity, simply choose 'Edit', 'Select...', 'All' (CTRL + A as shortcut), then select 'Effect', 'Normalize' and uncheck the 'Normalize maxium amplitude to -3 dB' option and click 'OK'.

    Once the normalize tool has completed, choose 'File', 'Export as WAV' to save in lossless format.

    Craig
     
  15. Johnny Blue

    Johnny Blue I made it to 'Member'!

    Craig

    That looks very interesting: I shall give it a go (not that I understand what 'Normalize' means or how it can remove the DC offset -- will it be visible on the waveform in Audacity that there's DC offset?).
     
  16. dave

    dave Plywood King

    Thanks for the DC offset verification Wylton (and you're welcome John.)

    I would have thought the odds would be almost 100% that some amplifier or other device somewhere in the recording studio would have blocking caps limiting bandwidth considering all of the different brands of equipment you'd typically find but it appears that 1% can sneak up and rear its head especially when combined with wide-band electronic synths, etc. making the music.

    FWIW, in the thirteen year lifespan of my CDS mk1 I never experienced this problem but very few disks in my collection have electric instruments of any sort.

    LinnAudio- you could always email Naim and ask if the CDS3 has DC offset protection if you're into electronica.
     
  17. stackowax

    stackowax pfm Member

    Hmmm. I wonder if this explains a similar problem I've had with a single disc on my Exposure CD player. It is a Stereophile test disc and it is a recording of a Fender bass guitar, first in the left channel (only) and then in the right channel (only). You can hear the Exposure's relay click on (and the sound cuts out) just as the Fender guitar starts up on the left channel. The right channel track plays all the way through without a hitch. As I say, I've never had this problem with any other disc and the disc plays straight through on my DVD player.
     
  18. dave

    dave Plywood King

    An email to Exposure would get you an answer for sure.
     
  19. wylton

    wylton Naim and Mana member

    As far as I know, the CDS1 is the only DC coupled player in the Naim range, so none of the others suffer this problem.
     
  20. dave

    dave Plywood King

    Makes sense Wylton, I wasn't aware of that. Thanks.
     

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