Grace 101 mic pre

Discussion in 'Preamps / Channel Strips' started by lawless, Jun 29, 2007.

  1. lawless

    lawless Guest


    I am the proud new owner of a grace 101 pre and was reading up on it.

    I came across this in a review by Bob Ross for Recording Magazine:

    "Both the XLR and TRS jacks can feed
    unbalanced sources, though Grace strongly recommends
    using cables which leave pin 3 (or the ring) open to minimize

    What are cables that leave pin three (Or the ring) open?
  2. Boswell

    Boswell Moderator Distinguished Member

    Apr 19, 2006
    Home Page:
    What the reviewer is talking about here is connecting the balanced output of the 101 to an unbalanced input of a mixer or ADC. This is a surprisingly common requirement if you want to feed an external pre-amp into the insert return point of a mixer in order to by-pass the mixer's pre-amps. If you were to use a conventional XLR-TRS, TRS-TRS or TS-TS cable, you would short circuit the negative signal to ground or another output. The excessive currents flowing in the negative output circuit would cause distortion in the positive signal, so best avoid.

    Depending on what unbalanced equipment you are feeding, an insert cable (TRS - 2x TS) can be used by plugging the TRS jack into the pre-amp output and the Send TS jack into the next piece of gear. The Return TS jack would be left open circuit, but make sure it doesn't touch anything, otherwise you are back to the high current situation. You can also buy XLR-TS (mono jack) cables, in which pin 3 of the XLR is left open circuit.

    These cables can't be used for the situation mentioned earlier of feeding the insert return of a mixer. In that case, you would have to make up a TRS-TRS lead with the ring connection disconnected at one (or both) ends. It's better to use a balanced-unbalanced transformer to meet this requirement.
  3. lawless

    lawless Guest

    Thank you for the detailed response. This forum rocks! :D

    Yes, I was planning on using the second balanced output of the Grace 101

    for zero latency monitoring by routing it (and the daw outs) to an old

    Yamaha 12 channel mixer I bought in the late 90's. Should I purchase a

    balanced/unbalanced transformer for this purpose or will the signal be

    usable? Also, I dont want to damage the gear...

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