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Thread: Feedback and Hiss

  1. Default Feedback and Hiss

    I own a DNS-112N powered by an Aguilar Tone Hammer 500 which puts out 250 W RMS into 8 ohms and 500 W RMS into 4 ohms. I would like advice on two issues.

    1) Last week I performed with an acoustic bass. The amp output was at 8, gain at about 5 and the bass was at 6. Suddenly I got feedback, a medium pitched howl. I ran to the amp and turned it off. It could not have been more than 10 or 15 seconds. Could the feedback have caused any damage, especially to the tweeter? Can feedback damage an amp?

    2) There is a hiss in my system. The more I turn up the treble (including the tweeter on the cabinet), the more hiss I get. You can 't hear it when I'm playing, but you can when I'm not. The hiss is there even if a bass is NOT plugged in. What causes this hiss? Could the feedback incident cause or worsen it? (I actually think it was there before the feedback incident.)

    Thanks in advance.

  2. #2
    Join Date
    May 2010
    Location
    Alberta, Canada
    Posts
    2,088

    Default

    The feedback is likely from the acoustic bass. When they are amplified the vibrations from your speaker often excites either the stage you are playing on, or it positioned behind the bass, the bass itself. Those vibrations are picked up by the bass and cycles through its piezo pickup (or mic, if that's how you are getting the signal) and voila, feedback. Your DNS-112 can handle a lot of power (900 watts peak at 8 ohms), so I don't think it would have been damaged by the feedback.

    This has happened a couple of times with my Steinheizer NXT5 electric upright. Never showed up while I was playing, but if I let the bass stand there, it would start to feedback on the open A string. I use my Eden amps for more than one instrument, so now have my electric basses connected to the amp input and my upright connected into the Effects Return, through my Eden WTDI preamp pedal, which allows me to turn the signal off with the footswitch. No feedback since then.

    I think you need to find a way to dampen the possibility of feedback by isolating the bass from the speaker cab, probably best done by changing the cab/bass locations.

    Have you tried the cab with a different amp? If the hiss is still there, it may be from the cab itself. If not, then it is something coming from your Aguilar amp. I'm not very familiar with your amp and don't know what I/Os it has, but I find that cleaning all the I/Os, front and back, with a cleaner like Caig's DeOxit will often clear up noise problems in amps. I do this cleaning once a year as part of my annual gear maintenance process. Spray the cleaner into each and every plug, then work a 1/4" jack in and out and around in the plug 15 or 20 times. Clean them all, even if not used because often the signal path goes through them even when not used. Crud and corrosion can build up on those contacts, degrading the system.

    My Eden amps have a semi parametric EQs, that lets me isolate fairly narrow frequency bands. This allows me to select a frequency band and cut the output there a bit. Didn't work well with my problem because in order to bypass the vibrations coming through the floor of the stage, I would have to cut the low mids just about entirely. Not good for the sound.

    I use that feature primarily to deal with bad room acoustics.

    Good luck.
    ___________________________________
    Steinberger NXT5 EUB, MTD 535 Fretless, Tobias Killer B6, 72 Fender Precision
    Eden WT500, WTX1000N & WP100, QSC PL230
    Eden D410XLT, D410XST, 215, Fender Bassman 10

  3. Default

    TobiasMan,

    Thanks for all the info. I don't often play my acoustic bass through an amplifier, so this was the first time I had any feed back and was mostly concerned about the damage I could have done to the amp or speaker. I don't have a second amp or cabinet, so I can't run amy comparison tests, but thanks for the idea anyway. BY the way David Nordschow said about the same as you regarding the feedback damage. Thanks again.

  4. #4
    Join Date
    May 2010
    Location
    Alberta, Canada
    Posts
    2,088

    Default

    David's the Man
    ___________________________________
    Steinberger NXT5 EUB, MTD 535 Fretless, Tobias Killer B6, 72 Fender Precision
    Eden WT500, WTX1000N & WP100, QSC PL230
    Eden D410XLT, D410XST, 215, Fender Bassman 10

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