Radial J48 issue with Pedalboard

Discussion in 'Effects [BG]' started by Zac Watson, Jun 25, 2019.

  1. Zac Watson

    Zac Watson

    Jun 25, 2019
    Hey all

    I’ve had an interesting situation come up when using a Radial J48 on my pedalboard.

    Basically I run 2 lines, one for electric and one for upright

    Electric line went: Bass>Pedalboard>J48 DI>Side A of A/B Switch>Amp
    Upright Line: Upright>Fishman Pro Eq>Side B of A/B Switch>Amp

    So here’s the problem: When I’m on side A, The J48 works fine, goes through to amp and live through desk, but when switch to side B not only does the thru cut out (as expected) but the XLR out stops working too. Given the A/B switch comes AFTER the through on the DI I don’t understand how this could happen.

    Any help would be appreciated.

  2. ak56


    Apr 2, 2015
    Carnation, Wa
    I've seen schematics of some A/B switches that are designed specifically for switching one input to one of two outputs (one guitar to one of two amps) but not one of two inputs to one output. What it does is puts a short across the unused output.

    Example, if a guitar is on the input, when switched to Amp A, it will place a short across the output B to reduce the possibility of noise from amp B, and vice versa.

    If used in your situation (two inputs to one output) when switched to B it will put a short across A, which is the output of your DI.

    I'm guessing your A/B switch is wired this way.
  3. Wasnex


    Dec 25, 2011

    To clarify for those who may not know, the Input and Thru of most DIs are just parallel jacks. You could easily plug your bass into the Thru and use the Input to send the signal to your amp. So if you short out the Thru, you also short out the Input. If the Input is shorted, no signal will be present at the XLR.

    J48 Block diagram
    ak56 likes this.
  4. Zac Watson

    Zac Watson

    Jun 25, 2019
    Thanks crew

    That makes total sense. It’s actually not a huge problem (just means I have an extra mute I guess) but it was bugging me that I couldn’t work out why it was happening.

    Wasnex likes this.