Tonearm Mass and Suitable Cart - was Choosing Hi-Fi Cart/Stylus

Discussion in 'rec.audio.pro' started by Doughboy, Sep 2, 2003.

  1. Doughboy

    Doughboy Guest

    I've found out that my Gemini PT-2000 has a tonearm mass of 9g, which
    is lower than the Technic SL1200's 12g.

    Does this qualify it as a high mass tonearm, therefore making carts
    such as the Ortofon 510 or 520, with their high dynamic compliance of
    25 µm/mN, or the OM 5E (20 µm/mN), unsuitable for use with this
    tonearm? (in which case, can I assume I'd be better of with something
    like the Ortofon OM DJ E considering it's lower dynamic compliance
    9µm/mN, not to mention it's better trackability)


    Doughboy
  2. James Boyk

    James Boyk Guest

    Doughboy wrote:

    > I've found out that my Gemini PT-2000 has a tonearm mass of 9g, which
    > is lower than the Technic SL1200's 12g.


    Is this the "effective" mass (diff. from total mass)? If so, that's fairly low.


    > Does this qualify it as a high mass tonearm, therefore making carts
    > such as the Ortofon 510 or 520, with their high dynamic compliance of
    > 25 µm/mN, or the OM 5E (20 µm/mN), unsuitable for use with this
    > tonearm? (in which case, can I assume I'd be better of with something
    > like the Ortofon OM DJ E considering it's lower dynamic compliance
    > 9µm/mN, not to mention it's better trackability)



    Is µm/mN numerically equal to the old compliance unit of 10^(-6) dynes / cm ? (I seem to recall that it is; am too lazy to figure it out for myself now.)


    What's the mass of these cartridges?


    James Boyk
  3. Doughboy

    Doughboy Guest

    On Tue, 02 Sep 2003 10:13:06 -0700, James Boyk <boyk@caltech.edu>
    wrote:

    >Doughboy wrote:
    >
    >> I've found out that my Gemini PT-2000 has a tonearm mass of 9g, which
    >> is lower than the Technic SL1200's 12g.

    >
    >Is this the "effective" mass (diff. from total mass)? If so, that's fairly low.


    Yes, Effective Mass (without cart) .

    >> Does this qualify it as a high mass tonearm, therefore making carts
    >> such as the Ortofon 510 or 520, with their high dynamic compliance of
    >> 25 µm/mN, or the OM 5E (20 µm/mN), unsuitable for use with this
    >> tonearm? (in which case, can I assume I'd be better of with something
    >> like the Ortofon OM DJ E considering it's lower dynamic compliance
    >> 9µm/mN, not to mention it's better trackability)

    >
    >
    >Is µm/mN numerically equal to the old compliance unit of 10^(-6) dynes / cm ? (I seem to recall that it is; am too lazy to figure it out for myself now.)


    I have no idea. I did notice that Grado still quote their carts in
    CU's, and quotes figures around 20, so probably.

    >What's the mass of these cartridges?


    If cartridge weight is the same thing:

    OM 5E - 5g
    510MK II - 5g
    520MK II - 5g
    OM DJ E - 5g

    Grado DJ100 - 5.5g



    Doughboy
  4. James Boyk

    James Boyk Guest

    Doughboy wrote: ...my Gemini PT-2000 has a tonearm mass of 9g...

    [cartridge mass & compliance]
    OM 5E: 5g, 20 µm/mN
    510MK II: 5g, 25
    520MK II: 5g, 25
    OM DJ E - 5g, 9
    Grado DJ100 - 5.5g, Compliance not given


    **
    Assuming

    (a) the compliance units are the same as the old-fashioned one,

    (b) I remember the formula correctly:

    Res. Freq. = 1000 / 2* pi * [sqrt [M*C)],

    then---



    OM 5E: 1000 / [6.28 * sqrt (14*20)] = 9.5 Hz


    510, 520: 1000 / [6.28 *sqrt (14*25)] = 8.5 Hz


    OM DJ E: 1000 / [6.28 * sqrt (14*9)] = 14.2


    Grado DJ100: can't calculate w/out compliance figure.


    Comment: The ideal range varies according to commentator, but no one puts it outside the range 10-14 Hertz. My preference is for 12-14. None of these quite fall in that range, but the OM DJ E is probably the most usable as getting the farthest from record
    warp (ca. 8 Hz) and footfall vibrations. I would not use the 510 or 520.

    Much depends on the isolation of your turntable. If it's not isolated from sound fields of the music its playing, then run the monitor level way down or use headphones.

    Of course there's more to a cartridge's performance than just this aspect. For instance, you might get a Shure V-15V/MR and use its damping brush. Even though it has high dynamic compliance, you might get better overall results with it than with any of the
    se.


    At some point you used the word "transcription." In the old days, this implied super-duper quality. If that's what you want, I doubt that any of this gear will give it.


    James Boyk
  5. Doughboy

    Doughboy Guest

    On Tue, 02 Sep 2003 15:20:01 -0700, James Boyk <boyk@caltech.edu>
    wrote:

    >Doughboy wrote: ...my Gemini PT-2000 has a tonearm mass of 9g...
    >
    >[cartridge mass & compliance]
    >OM 5E: 5g, 20 µm/mN
    >510MK II: 5g, 25
    >520MK II: 5g, 25
    >OM DJ E - 5g, 9
    >Grado DJ100 - 5.5g, Compliance not given
    >
    >
    >**
    >Assuming
    >
    >(a) the compliance units are the same as the old-fashioned one,
    >
    >(b) I remember the formula correctly:
    >
    > Res. Freq. = 1000 / 2* pi * [sqrt [M*C)],
    >
    >then---
    >
    >
    >
    >OM 5E: 1000 / [6.28 * sqrt (14*20)] = 9.5 Hz
    >
    >
    >510, 520: 1000 / [6.28 *sqrt (14*25)] = 8.5 Hz
    >
    >
    >OM DJ E: 1000 / [6.28 * sqrt (14*9)] = 14.2
    >
    >
    >Grado DJ100: can't calculate w/out compliance figure.
    >
    >
    >Comment: The ideal range varies according to commentator, but no one puts it outside the range 10-14 Hertz. My preference is for 12-14. None of these quite fall in that range, but the OM DJ E is probably the most usable as getting the farthest from record

    warp (ca. 8 Hz) and footfall vibrations. I would not use the 510 or 520.
    >
    >Much depends on the isolation of your turntable. If it's not isolated from sound fields of the music its playing, then run the monitor level way down or use headphones.
    >
    >Of course there's more to a cartridge's performance than just this aspect. For instance, you might get a Shure V-15V/MR and use its damping brush. Even though it has high dynamic compliance, you might get better overall results with it than with any of th

    ese.

    Thanks for the useful info. It does seem that the OM DJ E is my best
    bet. The Shure V-15V/MR (or even the M97xE) is too expensive for me.
    As for the isolation issue, I'll just use headphones to monitor when
    recording to avoid any complications, although I think the turntable's
    feet offer quite good isolation.

    >At some point you used the word "transcription." In the old days, this implied super-duper quality. If that's what you want, I doubt that any of this gear will give it.


    I probably shouldn't have used that word. I was just trying to convey
    that I want to purchase a cartridge suitable for making reasonably
    high quality recordings.



    Doughboy
  6. James Boyk

    James Boyk Guest

    Doughboy wrote: > Thanks for the useful info.


    You're very welcome.



    > ...It does seem that the OM DJ E is my best
    > bet. The Shure V-15V/MR (or even the M97xE) is too expensive for me.
    > As for the isolation issue, I'll just use headphones to monitor when
    > recording to avoid any complications, although I think the turntable's
    > feet offer quite good isolation.



    This is *extremely* unlikely. I've never seen feet that did. The only good isolation I've ever seen has come from a subchassis suspension a la Linn Sondek, AR or other similar turntables. But if the support is solid and there's no sound field for the turnt
    able to need isolation from, things should be copacetic, as we used to say here in the '70's.



    > I probably shouldn't have used that word. I was just trying to convey
    > that I want to purchase a cartridge suitable for making reasonably
    > high quality recordings.



    Of course I know nothing about these cartridges' sound quality, so you're on your own.


    Good luck.


    jb

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