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Isolating hiss in a DI

Discussion in 'Amps and Cabs [BG]' started by Lonnybass, May 31, 2005.

  1. Lonnybass


    Jul 19, 2000
    San Diego
    Endorsing Artist: Pedulla Basses
    This weekend at an event at a downtown Chicago hotel, I was told by the sound engineers that the DI was hissing on my Alembic F-1X (which is plugged into my Furman PL-Plus along with all my rack gear), and could only be solved by rolling off the highs at the board. This has happened a few times in the past, even when I switched over the ground lift on the front panel.

    What I'm looking for is some ideas in terms of how to quickly isolate and solve this problem in a time-is-of-the-essence environment. In this case, we had a limited time in which to finish soundchecking before the event was opened to guests.
    Quick fixes, solutions, ideas would be welcomed.


  2. LiquidMidnight


    Dec 25, 2000
    Are you sure that the hissing was being produced by your preamp's DI and not at the input level? If your bass is producing any hum either by its pickups or preamp, it will still be transferred through a balanced out.
  3. billfitzmaurice

    billfitzmaurice Commercial User

    Sep 15, 2004
    New Hampshire
    Owner, Bill Fitzmaurice Loudspeaker Design
    What are you using for speakers? Do you have tweeters? Is the DI post EQ? If you don't have tweeters in your cab (or they're turned off) and the DI is post EQ you'll get hiss in the PA that isn't being heard through your amp, as there isn't a tweeter there for you to hear it through. If you have tweeters and they're rolled off it's better to turn the tweeter pad up and the amp HF EQ down.

  4. My thoughts exactly.. I'm having a bit of a problem with my rig's signal going to the mixer. My cab doesn't not have a tweeter, and the 15s fall off in the high end to a point where I boost my highs on the head just to get a bit of high end. My DI is post EQ, and this sends a significantly bright sound to the mixer. I either need to get my cabs setup right, or go with less highs.
    With the extra highs at the mixer input, even a slight hum or buzz issue will be aggravated even more.

  5. DWBass

    DWBass The Funkfather Supporting Member

    My cure..............a simple passive DI box! I hate when I come back after setting up my gear and setting out my DI box and find the soundman has plugged into the DI on the back of my amp!! They end up telling me to turn down my amp and I end up telling them to use the frikkin DI box I set out for them! I prefer a clean signal going into the board. I find onboard DI's to be totally useless and should only be used if a separate DI box is not available!
  6. IvanMike

    IvanMike TTRPG enthusiast, Happy, Joyous, & Free. Supporting Member

    Nov 10, 2002
    Middletown CT, USA
    set the di on your alembic to pre eq. if you're using the bright control and/or boosting highs that will send some hiss to the di if it is in post eq mode.
  7. Very interesting.. What amp are you using? Just curious. I had previously thought that using an amp's built-in DI would be better, but maybe not..

    Where are you taking the signal from on the amp to the DI box? I'd like to hear more about this if you happen by again..

  8. DWBass

    DWBass The Funkfather Supporting Member

    Hartke HA5500. The FOH dude plugs an XLR into the DI on my amp and plugs directly into his mixer. It can give a pre or post signal but no matter what setting I put it on, he complained about my volume which was no more than 4!! I prefer sending a clean flat signal directly from my bass to the mixer board. This way, I can control my onstage amp the way I want. In addition, a lot of onboard DI have an inherant hiss eminating from them. In my experience, I've never encountered a quiet onboard DI!
  9. Lonnybass


    Jul 19, 2000
    San Diego
    Endorsing Artist: Pedulla Basses
    Well, in answer to the questions from earlier in the thread, my speakers are Acme B2's (with tweeters and midrange turned all the way up), my amp is a Stewart World 2.1 and I run the DI in "pre" mode through the Alembic F-1X, though I have a parametric EQ before it in the chain. Last night I switched it over to come after the Alembic in case that was what added the noise.


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