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bad noise in pre amp ?

Discussion in 'Preamps / Channel Strips' started by Smashh, Apr 24, 2015.

  1. Smashh

    Smashh Active Member

    Hi All ,
    I have a Presonus ADL 700 with a loud , white noise with crumpling paper in it when I
    use the instrument input.
    I have been using the mic input for guitar and bass since Ive had it , although if I tweak the EQs
    more than 2oclock I can hear a hissing comming back in .

    Anyone had this sort of problem ?

    What was your solution ?
    ( hope its not gonna hurt my pocket :cautious: )

    I can get a clean signal with phantom powered mic if thats of any help.
     
  2. DonnyThompson

    DonnyThompson Distinguished Member

    Assuming you have already checked the problem by process of elimination - obvious things like using a different guitar cable, etc., - it sounds like there's a problem with the unit. It could be a tube, or a bad instrument jack, I don't know if this model has transformers or not, it could be that too... But, adding in the other issue that you mentioned, where you are getting a noise when using the EQ, well, to me (I'm no expert, Bos would know far better @Boswell ) it sounds like the model needs serviced.

    How old is it? Is it still under warranty?
     
  3. pcrecord

    pcrecord Don't you want the best recording like I do ? Well-Known Member

    The mic and instrument input are of very different impedance. If you tried the instrument with everything bypassed or at nominal value and you still hear the noise, it points to some unit defects that will need to be checked by a repair shop. Of course we are talking about the guitar or bass strait to the preamp, no pedal etc..
    The last thing to check is the environement. I know that when I use an instrument input, I need to get away from the AC adapters I use and the monitors.

    It's a shame that this happens, the ADL700 is a great unit
     
  4. Smashh

    Smashh Active Member

    Yep soundz like Ill have to take it in and get it fixed . I'd love to have it working properly .
    Ive known of the prob for a while now but sorta bypassed it and kept it out a mind :oops:
    I bought it off ebay from the states and it may be still within warranty although Im not sure if
    it would still be covered .
    After the import taxes the Aus gov slapped on it , I should've bought a new one from here .
    Thanks for the replies guys , Ill check the paper work etc ... (y)
     
  5. Smashh

    Smashh Active Member

    Outta luck , warranty only covers original purchaser :eek:
     
  6. Boswell

    Boswell Moderator Distinguished Member

    Using the XLR low-impedance mic input is not going to give a very good result with a guitar, even if your guitar has a built-in pre-amp.

    Assuming you are using a standard TS guitar cable and not a TRS (balanced) lead to connect your guitar to the DI (instrument) input, are you up for doing a few easy diagnostics?

    For example, what happens if you plug in a simple TS jack plug on its own (with no cable) into the DI input? If you still get the "crumpling paper" sound, the ADL 700 is definitely faulty.

    If it's OK with just a jack plug, try the guitar cable plugged into the ADL700 but not plugged into the guitar. This will be very sensitive to movement of the cable, but you should be able to tell whether the crumpling paper noise is there.

    If that's OK, there's something amiss with your guitar pickup circuit when it drives a high-impedance input.
     
    DonnyThompson likes this.
  7. Smashh

    Smashh Active Member

    thanks Boz , I take the guitar lead out and I still hear the noise so definately something gone in the unit.
    I have a friend who does electronic repairs so Ill call in when hes in the workshop and let you know what it was
    assuming he finds the fault .:)
     
    pcrecord likes this.
  8. Boswell

    Boswell Moderator Distinguished Member

    That's odd, as I got the impression from what you said that the noise was absent when you used the XLR microphone input.
     
  9. pcrecord

    pcrecord Don't you want the best recording like I do ? Well-Known Member

    I think it's the DI input circuitry that has a problem...
     
  10. Boswell

    Boswell Moderator Distinguished Member

    I assumed you were talking about the jack plug in the ADL700 DI input, but do you mean when you unplugged the lead at the guitar end? Have you tried a different TS cable?
     
  11. Smashh

    Smashh Active Member

    I take the jack out at the instrument input on the adl700 and still hear the noise .
    Good experience for me , I wont buy on ebay like that again , knowing the warranty doesnt cover me , and the taxes .( unless its under 1k , thats the threshold here for import ) They even tax on the postage fee.
     
  12. Kurt Foster

    Kurt Foster Distinguished Member

    maybe send it to PreSonus and tell them what happened. they may be kind ....
     

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