Radial JDI - low output?

Discussion in 'Recording Gear and Equipment [BG]' started by FatherDH, Mar 11, 2009.

  1. Ok, heres the deal. I have been using a radial JDI for a few months and the soundguys at the venues I play all have told me it is giving them a really low signal. So today I plugged it into my MBOX to check the level. The XLR output is atleast 2X as low as the bass direct, and none of the pads are on. Is this just the way these DI's are, or is somthing wrong? Any suggestions on how to diagnose and repair? :confused:

    Also, when I push in the "speaker pad" nothing happens to the sound?

    Thanks in advance!
  2. What kind of bass are you using? I found using a JDI with a passive bass ended up with a pretty quiet output. I've since switched to the J48 (active) and the output is much higher.
    bassomane likes this.
  3. I use passive J's and P's. It is strange to me that the output is 2x less than going 1/4 via the "THRU" jack. Is this normal? Is the "speaker" pad supposed to actually make an audible difference?
  4. bongomania

    bongomania Commercial User

    Oct 17, 2005
    PDX, OR
    owner, OVNIFX and OVNILabs
    The speaker pad should absolutely make an audible difference of 20dB drop at the XLR output, but should not have an audible change via the Thru jack. In normal use though, yes any passive transformer-based DI will have a drop in signal level. IIRC with the Jensen in the JDI it's a 12dB drop. This is normal. For this reason it's often suggested that passive DI's be used with active basses that have higher output, especially since the JDI will not clip in an unpleasant way when fed a hot input, as many active DI's will.
  5. Thanks for the info bongomania! I am wondering if something is wrong with the "speaker" button, maybee it is stuck on? I can't really measure the dB drop, but to my ear it sounds alot more than a 12dB difference. I can push the Speaker pad button in and out, but it makes no change in sound or volume. I sent an email to Radial, hopefully they will provide a solution.
  6. In case anyone cares here is the answer I recieved from Radail. They were quite helpful in helping me understand what this thing actually does. Thanks Radial!

    "the JDI is a passive device ( it requires no power ). It uses a transformer to Convert a unbalanced high impedance signal to a balanced low impedance mic level signal. This is done so you can run long lengths of cable without picking up any hum or noise. The Signal coming out of the JDI is meant to be plugged into a mic pre-amp. Your M-Box is Probably expecting to see a balanced line level. The output of your Bass is a unbalanced instrument level. This is usually at about -20dB. This will be the same as the thru output. The thru is Just wired in parallel to the input. The signal coming out of the JDI is around -30 – 40 dB or mic level. This is due to an insertion loss in the transformer. The speaker switch is meant to be used in Conjunction with the pad switch if you use the DI on the speaker out of your amp. It will have Little or no effect if used on its own."
    _Obra_ likes this.
  7. bongomania

    bongomania Commercial User

    Oct 17, 2005
    PDX, OR
    owner, OVNIFX and OVNILabs
    Oh yes, I forgot that the pad switch and speaker switch were separate.
  8. mattattack187

    mattattack187 Bass Enthusiast Supporting Member

    Feb 2, 2012
    Ellsworth, ME
    Apologies about reviving an old thread but I'm new to the Radial JDI and I run a preamp into it and use primarily passive basses. I have to add a +20db gain to get about the level I'd get from my Sansamp plugged in to the mixer. The Sansamp I usually have to lose about 15 to 20db. Does that sound right? I figure because it's passive it would need a little extra push.

    Thanks guys.
  9. This is fine. The JDI drops the signal 22dB* from the input to the XLR so in order to get the same level at the mixer that gain needs to be made up somewhere.

    *The transformer ratio is 12:1 which is equivalent to ~-22dB.
    mattattack187 likes this.
  10. mattattack187

    mattattack187 Bass Enthusiast Supporting Member

    Feb 2, 2012
    Ellsworth, ME
    Thanks. If my little Samson mixer can up the gain then there should be no reason a gig PA can't.
  11. beans-on-toast


    Aug 7, 2008
    It's important to note that with a JDI, you can use the input pad on its own. The speaker option needs to be used with the pad engaged otherwise it isn't connected into the circuit.

    The JDI's pad is -15db. The speaker switch engages a band pass filter, which cuts hights and lows, so there will be some loss from that as well. They claim that this simulates the rolloff of a guitar speaker. With the pad and speaker on, the signal is routed from the input, through the bandpass circuit, then through the pad, then into the transformer and out through the XLR.
    Last edited: Jan 13, 2017
  12. Uche_bass


    Jul 31, 2017
    Is the speaker sim any good? I'm wanting to get a di to go direct to the board. I have an active bass and it has all the eq I need, then I'd go through one or two pedals at most and then the di. Good idea or better get a sansamp? (Just for the speaker sim, I don't care about the eq and drive on the sansamp)
  13. AngelCrusher


    Sep 12, 2004
    Mesa Boogie, Tech 21, Taylor
    @mattattack187 Passive bass needs to be paired with an active DI like a Countryman. Active bass is best with a Passive DI.

    That will fix the issue.
  14. beans-on-toast


    Aug 7, 2008
    People like what it does given the low cost. The heart of the unit is a very good Jensen audio transformer. Is it any good? It works for me. Some DI’s do this to limit the energy in the low end of the signal, it allows the DI to handle more power if it is connected in parallel with the speaker. If you don’t do this, the bandpass filter is not inserted.

    If you are looking around, a nice DI to check out is the Rupert Neve RNDI. They know how to do transforms very well. This is an active device and is powered by phantom power on the XLR.

    RNDI: Rupert Neve DI
  15. BlueLou


    Oct 26, 2017
    I know this is a older thread but thought I might share this info.
    There is a great 5 part video set available on YouTube
    that really does an excellent detailed explanation teaching all about DI's
    Really worth watching.