rpm's

Discussion in 'Music Corner' started by trilogia, May 24, 2002.

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  1. trilogia

    trilogia New Member Thread Starter

    Location:
    Davenport, Iowa
    me and my dad were talking about the rpm's on a record last weekend. like how does it read the same speed towards the center of the record as the outside edge of the record? you would think the information would be hitting the needle faster towards the center of the record wouldnt you? do they cut them with this in mind or how the hell does that work exactly? anyone know?
     
  2. Grant

    Grant Life is a rock, but the radio rolled me!

    Simple. The grooves are spaced closer together as the needle (stylus) moves toward the center of the record.

    CD players simply slow down because the lines of pits need to be spaced evenly across the disc.
     
  3. Dave

    Dave Esoteric Audio Research Specialistâ„¢

    Location:
    B.C.
    Grant,

    Can you please explain in fuller detail how this grooves spaced closer together thing works? I would think that if they got closer it would spin faster.:confused:
     
  4. Grant

    Grant Life is a rock, but the radio rolled me!

    The record spins at a constant rate. The more imformation you fit onto a record, the closer you must space the grooves near the end. Given a comortable enough space, the engineer can cut more bass, which means bigger grooves. There is more area to work with. The more dynamic cuts, or cuts with more of a frequency range are usually at the beginning of a record. As you move in closer the volume may be decreased or the music may be compressed. The engineer may opt to slash bass frequencies to ensure that the grooves are cut cleanly and that the stylus doesn't jump out of the grooves. The longer the side, the harder it is to cut. If a producer is smart, he/she will regulate the mellower tracks to the end of the side, particularly if the program is long. I've noticed a lot of 70s disco LPs have increased distortion on the inner grooves. Bad vinyl, worn stampers, loud cuts on the side ends, and wear from a bad, damaged, or lightly tracking cartridge are all too common.

    Using a good stylus/cartridge and a good tracking force can minimize this. A side benifit of using a good stylus and/or tracking at the upper range of the recommended grams is that you can cut through a scratch so the record won't jump or skip. I play near-mint, to worn-out vinyl and I rarely ever experience a skip!

    The difference is in the mastering. A good mastering engineer would adjust the volume of an LP side so it is consitient with the program material if compression or EQing are used. If the music is right and the disc is cut well, you may not notice the dynamic shift as the record nears the end of a side. A good way to avoid much of this is to simply keep the program material down to around 15-17 minutes.

    As TP will even tell you, a fresh or young stamper should yeild a good disc that will play cleanly. using good vinyl helps a heap too.

    After doing literally thousands of vinyl to CD-R transfers, as I have, one really gets to know the quirks of the LP and it's playback. And you guys thought I didn't know a thing about vinyl!:D

    With the CD, the evenly-spaced pits must be read at a constant rate so it is the disc that must be slowed down. It gets slower instead of faster because the data is read from the center out.

    Steve Hoffman. how am I doing?
     
  5. Dave

    Dave Esoteric Audio Research Specialistâ„¢

    Location:
    B.C.
    The cd part makes perfect understandable sense. The record playback requires a bit more thought, but it makes sense. THX Grant.:)
     
  6. srigby

    srigby Active Member

    Location:
    Holden Beach, NC
    Grant
    What software do you use for your vinyl to CD-R tranfers?

    Scott
     
  7. Mike V

    Mike V New Member

    Location:
    Connecticut
    Hi folks,

    The platter may be revolving at a constant (more or less) 33 1/3 rpm, but that is not the velocity (if you will) the needle is tracing your record grooves. If you did a simple calculation, measuring the radius from your spindle to the outer playable part of your lps (just shy of 6"), you would discover that the velocity your needle travels within the groove is far less once that needle starts to trace grooves at a radius much closer to the spindle (say 4"). That's why I never bought this "infinite sampling" argument from some people. The "mechanical sampling", if you will, decreases immensely as you approach the inner grooves of an LP. Then you can run into trouble with unpleasant distortions, graininess, etc. These problems can be avoided (or minimized) when a master cutter (like Kevin Gray or Bernie Grundman) is at the helm. I don't know how they do it, but I'm sure Steve could pipe in with some specifics (pretty please?). I'm guessing there are at least a dozen major factors involved (cutting levels, source material, laquer quality, cutter head design & amps to drive it, plating, vinyl quality, etc, etc...). Not to mention all the critical minutiae that separates the men from the boys ;) .

    Mike
     
  8. Grant

    Grant Life is a rock, but the radio rolled me!

    I use a PC. I use Cool Edit Pro and Sound Forge 5.0.
     
  9. Grant

    Grant Life is a rock, but the radio rolled me!

    I would also like Steve's input here. After all, he cuts LPs!
     
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