Looking for a LOMC cartridge that sings at 100 ohm input impedance

Discussion in 'Audio Hardware' started by LostArk, Jul 21, 2021.

  1. Benzion

    Benzion "Cogito, ergo sum" Forum Resident

    Brooklyn, NY
    His Jelco arm is fluid-damped, it might help with the slight resonance mismatch.
    chervokas likes this.
  2. Benzion

    Benzion "Cogito, ergo sum" Forum Resident

    Brooklyn, NY
    What do you mean it doesn't? That round thingy on top is the cap of the oil reservoir. I own an Audioquest PT-6, which is an OEM Jelco-250St - there is oil damping on it.
  3. Davey

    Davey NP: Merope ~ Salos

    SF Bay Area, USA
    Oh, that's great, sorry for the misinformation, they don't say anything about it in the Jelco SA-250 instructions so I assumed it didn't have the oil cup under the cap. I wonder why they didn't advertise or talk about that feature? It's not just on the straight arm, right, you mean they all have it? Guess I've never seen one with the top cap removed :)

    So you just unscrew the cap on top of bearing housing and add some oil in a cup?

    Last edited: Jul 22, 2021
  4. chervokas

    chervokas Forum Resident

    If it is, likely so, yeah.
  5. Benzion

    Benzion "Cogito, ergo sum" Forum Resident

    Brooklyn, NY
    Yes. The Audioquest PT-6 is a straight version of Jelco 250, and there is oil in it.
  6. avanti1960

    avanti1960 Forum Resident

    Chicago metro, USA
    the effective mass is kind of high for the AT, i found 13.4 G which gives a best case 7.1 Hz resonance. With a damping mat like a herbies excellent i would try it but you are on the fringe but could be ok. i dont think it is such a black and white situation but cartridges are hard to return.
    i would search art9 users to find if they have had success with a 13G tonearm. i bet yes. big thread on audiogon.
    5-String likes this.
  7. MarkD51

    MarkD51 Well-Known Member

    Yes, I have often heard the 10X rule for loading.

    And as some mention and is true, it can be system dependent.

    Also, there's no hard, fast rule, and no harm or foul loading a cartridge to your personal hearing tastes and likes.
  8. MarkD51

    MarkD51 Well-Known Member

    About the only minor difference to note is there is a slight difference in specs as far as length and S-P distance for the AQ PT-6-7-8-9 versus the 250ST. I think a 1mm or 2 difference, small I know.

    Jelco made Arms for many other companies who then slapped their name on it, Sumiko was one, and might have been some slight differences in finish, in Arm wand Damping,etc.

    Another example, was the Graham Robin, a sort of rare Arm that was Jelco Based. Some parts were Chrome Plated, and again I believe different length and S-P specs from either Jelco or AQ.
    patient_ot likes this.
  9. Lowgroove

    Lowgroove Forum Resident

    I think the 509 has the same phono preamp as my 590.

    I have used a Dynavector XX2 and a Hana ML with my internal phono preamp and both sound great.

    With the Dynavector I compared the internal phono stage to a Dynavector P75 Mk3 (at both 100Ohm and PE loading) and the Luxman sounded better than the P75. I haven't tried with the Hana.

    I am looking for the future to purchase a better external phono stage, but the internal one works very well with these carts in the meantime.
  10. chervokas

    chervokas Forum Resident

    Well, there can be "harm" if the load on the cartridge is too close to the internal impedance of the cartridge in the form of excessive voltage loss at the input of the phono stage. Considering that you're trying to amplify a very low voltage signal, it's really self-defeating to add voltage loss from an extreme resistance load. That's quite apart from consideration of the impact of the resistance load on the amplitude of the cart/preamp RLC circuit. Having a load impedance being 10X or more a source impedance is good practice to minimize voltage loss at the load for phono carts, but not just for phono carts -- for amps as load and preamps as source; for preamps and loads and CD players as source, etc.
    patient_ot likes this.

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