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Dumb Question about Mono Vinyl Playback

Discussion in 'Audio Hardware' started by teaser5, Mar 11, 2005.

  1. Allan Songer

    Allan Songer New Member

    Location:
    Hollywood, CA
    Mono rules!
     
  2. jackieboy

    jackieboy Forum Resident

    Location:
    Philadelphia Pa.
    mono Needle drops

    Guys when I do a Mono Needle drop I use the Y cord to sum. they sound great.

    I used a tip from another thread (Beatles Cd singles box) from member "another side", to test true mono after. In my editing software I inverted the one channel then collapsed to mono. They should cancel out to silence. they do not.

    Which led me to cut and paste one channel to have a true mono needle drop. I gotta say these drops I'm making sound tremendous.

    I've been listening to Bob Dylan for 30 years and I feel I am very close to the essence of what these albums are about. A Simple Pure sound. Mono.

    But I do not understand why after I sum the channels they are not the same.Why are there still phase issues after R+L sum via Y cord?


    Thanks
     
  3. lukpac

    lukpac Senior Member

    Location:
    Milwaukee, WI
    Because you're still technically doing two A/D transfers - one for the left channel, one for the right channel. Even if the analog signal is exactly the same going in, you'll still get very small differences.

    Where are your Y cords? Between the TT and your preamp, or between your preamp and your sound card? If it's between your TT and your preamp, your preamp could be causing small differences between the channels.

    FWIW, I tried the Y cords setup once, but I've found things work better if I just record in stereo and then sum to mono after any declicking. Declicking works better that way, plus I have the option of picking only one channel if necessary. I've had a few cases where there will be noise in one channel but not the other, so I simply pick whichever channel is better.

    YMMV.
     
  4. ress4279

    ress4279 Forum Resident

    Location:
    PA
    Can anyone recommend a number of cheap to relatively expensive ($50-$200) mono cartridges?
     
  5. DrJ

    DrJ Senior Member

    Location:
    Davis, CA, USA
    So here's another probably dumb question related to the original one! :)

    I've been home demoing a Whest phono stage. In making some test needle drops of mono LPs, when I used the regular mono switch on my preamp, it sounded weird, almost out of phase like you'd get if you folded down stereo. When I instead used the selector switch on my preamp to choose either channel A or B for playback (rather than summing them) I got great mono sound, dead center placement, and none of the weird out of phase effect.

    The Whest is a dual mono design...does this have anything to do with why using the regular mono switch on my preamp with it gave such an odd result?
     
  6. soundQman

    soundQman Forum Resident

    Location:
    Arlington, VA, USA
    It is just the fact that summing L+R channels if they are not identical (not true mono) or are out-of phase can give you bad sound. Selecting one channel L or R for mono, like with your selector switch is the correct way to handle it. Dual mono design typically just means separate power supplies and maybe separate circuit boards for each channel in the preamp. In other words, potentially better isolation between channels. It wouldn't have anything to do with your problem, I don't think.
     
  7. bangsezmax

    bangsezmax Forum Resident

    Location:
    Durham, NC, USA
    At that price range, I think the Denon DL-102 is your best bet.

    Most other mono carts in that range are simply variations on standard stereo carts. The Denon was designed from the ground up for mono.
     
  8. ress4279

    ress4279 Forum Resident

    Location:
    PA
    http://www10.big.or.jp/~dh/codo/arm/arm3.html
    The DL-102 cartrige is used by AM radio stations. The DL-102 is not for mono LP's :confused: nor is it for 78 RPM records.
    Instead, the DL-102 is specially designed to output a mono signal from a stereo LP, so there is no danger of damaging a modern LP by its use.
    DENON recommends three gram as the best tracing force for DL-102.

    Is this simply a difference of opinion or is the 102 a best case compromise? It sounds like a great deal at $150.
     
  9. Another Side

    Another Side Forum Resident

    Location:
    San Francisco
    Tony, I have a similar problem with my tuner. The mono button on your preamp may not work as it should.

    I used to hear a similar sound, and for a long time I wondered exactly what the problem was. Until one day when I was playing my Highway 61 Revisited mono with the mono button pressed, I noticed that it sounded very strange. It turned out that the head shell was not attached properly and there was only sound out of one channel. But the odd thing was, that even though there was only sound out of one channel coming from the TT, the mono button was only partially summing the two channels. One channel was still much louder than the other. Since then I bought a double Y connector and it sounds quite a lot better.
     
  10. DrJ

    DrJ Senior Member

    Location:
    Davis, CA, USA
    Hi Jorge and Harold - well the problem with your theory - and I do appreciate your trying to help by the way! - is that I don't have that problem with the mono switch when I use it with the preamp's built in phono stage...when I use it then it's perfect, dead even output from each channel and it sounds fine, no phasing stuff. Sorry that I had forgotten to give you that important piece of info in my post.

    This phasing thing is only a problem with the Whest, when I run it through the preamp's line stage and then use the mono switch. So I don't think it's a problem with the switch per se. Oh well...weird.
     
  11. soundQman

    soundQman Forum Resident

    Location:
    Arlington, VA, USA
    Tony,

    It's hard to know what your problem might actually be if it is in the equipment, but I will say this: If you are playing mono vinyl, it is best to just play one channel or the other through your amps, using the selector switch you described. The reason is that you will get a cleaner sound than if you combine the two channels together (L+R), even if identical signals were used for left and right from a mono tape head during mastering. Why? Most mono record mothers/stampers after the mid sixties or so are cut with a stereo cutting head (which cuts laterally as well as vertically), which means they will produce slightly different signals left and right when played with your stereo cartridge. The exception to this would be if you had a true mono cartridge/stylus and are playing an older mono-cut (vertical cut, unidirectional) record from before the stereo era. But with stereo-cut mono records, some tracing distortion will therefore inevitably be introduced by cartridge mistracking and will be amplified and played back superimposed along with the music signal. I've tried this myself because I have a L/R selector switch on my preamp and it makes a difference as to how clean it sounds, no doubt about it. I can also set things up to listen to the left minus right difference signal on my preamp. When I do this I can hear all the grunge underneath that is eliminated by choosing one channel.

    Of course with mono compact discs, this doesn't apply, unless they screw up the phasing by playing back mono material on a stereo tape head during mastering. This is what happened with the Beatles Singles Box, and they didn't even have the tape heads aligned properly, which made it even worse.
     
  12. Mister Charlie

    Mister Charlie "Music Is The Doctor Of My Soul " - Doobie Bros.

    Location:
    Aromas, CA USA
    So when transferring a mono recording to the computer, in the audio editor I end up with a L+R set of tracks of mono (both trakcs appear the exact same on the waves). I could delete one side of the track (either L or R) and then simply have just one mono track before boiling it down to an mp3 or flac or what have you. Is that the preferred way to do it? Are there too many problems with 'stereo' mono tracks if you don't really need two tracks for one actual sound source?
     
  13. lukpac

    lukpac Senior Member

    Location:
    Milwaukee, WI
    Is this with or without Y-cords?

    If it's without, it can be helpful to have both. Sometimes one channel sounds better than the other, so you can pick and choose. Or you can digitally sum to mono if necessary. On one mono LP I have, side 1 sounded better summed to mono (with extra manual de-clicking before doing that, something you can't do with Y-cords), while side 2 had more noise in one channel. There I just used one channel, except a few small places where I summed the two channels to reduce distortion on strong sibilance.
     
  14. Mister Charlie

    Mister Charlie "Music Is The Doctor Of My Soul " - Doobie Bros.

    Location:
    Aromas, CA USA
    Without Y cords. Just any mp3 or wav or transferred stereo into the computer line in situation.

    The program (Audacity) will usually show a cut as two discrete tracks, even if it's the same mono information. I have noted I could pick and choose which one to keep/delete and sum, but I just wondered if leaving many mono cuts in two channels was a bad thing or not...I suppose it depends on how each one sounds.
     
  15. soundQman

    soundQman Forum Resident

    Location:
    Arlington, VA, USA
    I read these discussions and I keep scratching my head over why so many folks try to keep two channels going (left and right), when it's mono source material to begin with. I don't get it. It seems to me what you want is one channel of source material split and sent to both channels of amplification and from there to the speakers, rather than summing L+R. Why the obsession with summing the two channels at the source if they are not stereophonic to begin with? Just pick one or the other. If they are essentially the same but ever-so slightly different because of the mechanics of playback, as is the case with mono LP playback from a stereo cartridge, this method will give you less distortion. If a CD is true mono, then it won't matter either way, but you might as well set up your rig so you can play it that way for both types of media. With the computer situation I believe I have made mono .wav and MP3 files in the past at times, when I set up the extraction functon and sampling parameters for CD extraction. I don't think it has to be 2-channel, although that may be the default setting with some software. Maybe some of the more sophisticated music editing software programs set everything up as two channels (or more) to work with - I don't have any experience with those. I use a Mac with iTunes for occasional file extraction and CD burning, and I just assumed those basic options were available with Windows XP or third party burning software, or am I wrong about that?

    Just my two cents worth. :)
     
  16. Steve Hoffman

    Steve Hoffman Your host Your Host

    THE NOISE ON A MONO RECORD IS ALSO IN STEREO, if you just take one channel or the other you still have a bunch of noise that you would not get if you summed the two channels and took that. TRY IT; you'll understand.

    Do this: Take an LP (any LP mono or stereo) and just play the lead in groove. Make a dub of 5 seconds of it in stereo. Now COMBINE the channels and make a 5 second dub of it. Lastly, pick a channel, right or left, your call, and make a 5 second dub of that. COMPARE ALL THREE. Notice how the summed noise is much lower than the one channel you picked or the stereo? That's the reason to sum the channels.

    DO NOT DO THIS WITH COMPACT DISKS!!!!
     
    Michael P and 2xUeL like this.
  17. lukpac

    lukpac Senior Member

    Location:
    Milwaukee, WI
    Depends on the record, of course.

    Sometimes the noise will be reduced, while other times you'll get more noise if one channel has more noise than the other.
     
  18. Steve Hoffman

    Steve Hoffman Your host Your Host

    I'm assuming for purposes of a test that the record is basically clean.
     
  19. lukpac

    lukpac Senior Member

    Location:
    Milwaukee, WI
    I don't mean clean/dirty. I mean either a pressing issue or wear.
     
  20. bangsezmax

    bangsezmax Forum Resident

    Location:
    Durham, NC, USA
    I think that's a case of Japanese not translating that well into English. :)

    Yes, the DL-102 was designed for playing back stereo records and outputting a mono signal. But it works beautifully on mono records. Check the Vinyl Asylum for more opinions (you'll see mine over there too).
     
  21. soundQman

    soundQman Forum Resident

    Location:
    Arlington, VA, USA
    OK. I kind of get that. But this means the stereo "noise" you are talking about is more or less out-of-phase so that much of it cancels when you sum the channels. I wouldn't have thought of that, but I'll try it now. Thanks for straightening me out, Steve. :righton:
     
  22. Tony Plachy

    Tony Plachy Senior Member

    Location:
    Pleasantville, NY
    OK, Maybe I can help explain this with just a little math and science. Think of the noise as a small signal. If the noise in each channel (left and right grooves) is truly random then the noise signal from the left and the noise signal from the right are uncorrelated. The rule for summing uncorrelated signals is to square each add the squares and take the square root of the sums. If the noise signal from each channel is the same size or value as the noise signal from the other channel then the summed noise signal is the square root of two the the single channel noise signal. Now the real signal in each channel is the same in each channel of a mono record. They are 100% correlate signals and their sum is simply two times the single channel signal. So if we calculate the summed signal to noise ratio (S/N) we have twice the single channel signal divided by the square root of two times the single channel noise. That gives a summed S/N ratio that is the square root of two time the single channel S/N. The square root of two is a little more than 1.4. So by summing you get a 40% improvement is S/N over not summing. It's cool how mother nature works sometimes. :cool:
     
    2xUeL likes this.
  23. soundQman

    soundQman Forum Resident

    Location:
    Arlington, VA, USA
    OK, Tony that's cool. I appreciate that explanation. But here's one thing I'm wondering about still. I have a blend control on my preamp so I can listen to left minus right - the difference signal. Now when I play a mono vinyl record and use the blend control it doesn't cancel out to zero like it would with a mono CD. I hear background noise AND a very small amount of tracking distortion from the music signal because the cartridge doesn't track exactly the same, or the record isn't cut absolutely the same left and right. I can minimize this distortion by setting the anti-skating force and the azimuth correctly (in fact this control is a very useful tool for doing just that) but it is never completely zero and in fact may even vary slightly depending on where the stylus is on the record surface as it moves from outer edge to center.

    So it seems to me that picking one channel instead of summing them would therefore both reduce distortion in the signal and increase the background noise. I suppose the noise would be the more advantageous thing to reduce by 40% in most cases, assuming you have a clean record and a properly aligned tonearm and cartridge.
     
  24. vanmeterannie

    vanmeterannie Forum Resident

    I think you're hearing the effects of standard tonearm alignment; theoretically at the two null points the signal should cancel, but everywhere else there's a slight time difference because of the offset of the stylus from the groove , the way I understand it (which could be wrong).
     
  25. soundQman

    soundQman Forum Resident

    Location:
    Arlington, VA, USA
    You are correct about the two null points, and the signal theoretically SHOULD cancel perfectly at these points and nowhere else - but in addition to this consideration there may be slight manufacturing imperfections in the vinyl itself as well as imperfect behavior in the tracking performance of tonearm/cartridge in the grooves. It is a mechanical device, after all.
     

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