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Thread: Pre to power connection

  1. #1
    Join Date: Aug 2012

    Location: North East

    Posts: 3,675
    I'm Steve.

    Question Pre to power connection

    Do you think i would get away with a 3 metre interconnect between my pre-and power amp? Phono to Phono.

  2. #2
    Join Date: Apr 2009

    Location: Near Saffron Walden, Essex

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    I'm Dave.

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    Shouldn't be a problem with a sensible cable, depending on the pre.

  3. #3
    Join Date: Feb 2008

    Location: Near Accrington, Lancs, UK

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    I'm Ralph.

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    I have eight metre ICs between my pre and power. No probs.
    Ralph.

  4. #4
    RothwellAudio Guest

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    The resistance of 3 meters of cable would be negligible. The capacitance would be about 300pF (less with top notch cable). The output impedance of the pre-amp would have to be 26k to cause a high frequency roll-off at 20kHz. I doubt very much that your pre-amp's output impedance is so high. It's more likely to be less than 2k, in which case the HF roll-off would over 200kHz. Even a passive pre-amp made with a 20k pot has an output impedance of 5k or less.
    As long as the cable is screened there shouldn't be a problem.

  5. #5
    Join Date: Apr 2008

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    I'm Clive.

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    Active pre or passive pre? Probably it'll be fine either way though passive might possibly need checking out.
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  6. #6
    Join Date: Jan 2013

    Location: Birmingham

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    I'm James.

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    Quote Originally Posted by RothwellAudio View Post
    The resistance of 3 meters of cable would be negligible. The capacitance would be about 300pF (less with top notch cable). The output impedance of the pre-amp would have to be 26k to cause a high frequency roll-off at 20kHz. I doubt very much that your pre-amp's output impedance is so high. It's more likely to be less than 2k, in which case the HF roll-off would over 200kHz. Even a passive pre-amp made with a 20k pot has an output impedance of 5k or less.
    As long as the cable is screened there shouldn't be a problem.
    Interesting that RCA phono interconnects can be run ar reasonable lengths without too much loss or negative effect.
    Can you explain why so many of the high end manufacturers are using balanced XLR connections when to get any benefit all cables in your system from source to end need to be XLR?
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  7. #7
    RothwellAudio Guest

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    IMO the use of balanced connections in a domestic audio situation is complex and contentious. It's a huge topic and I'd rather not go into immense detail but high frequency roll-off is a function of source impedance and cable capacitance - balanced or singled ended makes no difference.
    The main advantage of a balanced line is noise rejection and that can be very important in a TV studio or a live venue but shouldn't really be an issue with 1m cable runs in a domestic setting.
    Just to be a bit cynical for a moment (not like me, surely ) I think XLRs are sometimes used simply because they give the impression of being more professional, more serious and just "better".
    Last edited by RothwellAudio; 20-01-2017 at 12:41. Reason: typo

  8. #8
    Join Date: Oct 2012

    Location: NE England

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    I'm Jez.

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    Totally fine even with a passive. I often use a 10K passive with 8m of cable....
    I'm with Andrew on the balanced option also. It's superfluous in domestic audio. Not only that but in many cases the equipment to be connected by balanced means is not truly balanced and the signal must pass through several op-amps to make it balanced at the sending end and then again at the receiving end to unbalance it.
    This is sometimes done by a "line driver" IC and "line receiver" at the other end, which in fact contain the same circuitry as the op-amp circuitry.
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  9. #9
    Join Date: Aug 2012

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    I'm Steve.

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    Thanks chaps. Grateful for the advice.

  10. #10
    Join Date: Jan 2013

    Location: Birmingham

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    I'm James.

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    Quote Originally Posted by RothwellAudio View Post
    IMO the use of balanced connections in a domestic audio situation is complex and contentious. It's a huge topic and I'd rather not go into immense detail but high frequency roll-off is a function of source impedance and cable capacitance - balanced or singled ended makes no difference.
    The main advantage of a balanced line is noise rejection and that can be very important in a TV studio or a live venue but shouldn't really be an issue with 1m cable runs in a domestic setting.
    Just to be a bit cynical for a moment (not like me, surely ) I think XLRs are sometimes used simply because they give the impression of being more professional, more serious and just "better".
    As I suspected.
    Main system : VPI Scout 1.1 / JMW 9T / 2M Black / Croft 25R+ / Croft 7 / Heco Celan GT 702

    Second System : Goldring Lenco GL75 / AT95EX / Pioneer SX590 / Spendor SP2

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