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Urei LA 4 silverface need help

Discussion in 'Pro Audio Equipment' started by KB, Sep 6, 2004.

  1. KB

    KB Guest

    I just got a pair of Urei LA 4 in my home studio when I patch it to my Mackie board... the sound that comming out is very bright and clean (lack of bottom also) I'm not sure that this kind of sound is the character of the LA 4 or not. Coz' when I listen to my old Urei 1178 I can tell unit have character not like LA 4. Do I miss anything like... little modification at the out put strip or....this unit is not in the good shape? (All function is working as I can see)
    Anybody who use to work with LA 4 please help.
    Thanks
     
  2. EricK

    EricK Guest

    Sounds like you may have a problem there. You make it sound lile the LA4 is acting like a high pass filter. If thats the case, I'd get it checked out.
     
  3. KB

    KB Guest

    Do you have any idea what part need to be replaced?
    What strange is both units have the same sound. ???
     
  4. EricK

    EricK Guest

    No unfortunately I have no idea what could be wrong. It does seem odd that they are both that way, but you never know. Where did you get them from?

    I assume you are interfacing them with the Mackie through the TRS insert jacks? If so, how are your cables wired, what connections are you using on the barrier strip?
     
  5. AD202

    AD202 Guest

    Hi,

    The LA-4 has a transformer balanced output stage. When connected to an unbalanced input, you have to make sure that you wire it correctly. If it's wired wrongly (which it sounds like it is) then only one side of the transformer is connected to the insert. What you're hearing is the leakage capacitance within the transformer from one side of the transformer to the chassis ground. It's highly unlikely that both LA-4's have the same fault, but more likely that the outputs (and possibly the inputs?) are wired wrong. Check the wiring diagrams on page 14 of this PDF of the LA-4 manual:

    UREI LA4 Manual PDF

    Hope this helps!

    AD
     
  6. KB

    KB Guest

    I've plug 1/4" jack at the insert socket of Makie board. Connection at the strip out put are look like this...

    COM +/- (out put strip) go to TIP
    Ground go to Sleve jacket
    COM +/- (In put strip) go to Ring

    May be I have a wrong wiring at the back of LA 4 I'm not sure..
    Thanks everybody for your help.
     
  7. AD202

    AD202 Guest

    Hi,

    The connections you've made are the problem- if I understand the way you've written it you've connected "Com" and "+/-" together to the tip of the insert for the "out" and the same for the "in" on the LA4?

    Have a look at this diagram from the manual:


    Click Here

    The "Grd" connection is the Chassis Ground, and the signal actually appears across the "+/-" and "Com" terminals- so with this wiring at the moment the inputs and outputs are effectively shorted out! Disconnect the wiring and do it as in the diagram above.

    Shorting the output probably won't have done any damage internally unless it's been left on with the output level whacked up for a period of time.

    Also (check your manual) but I have a feeling that Mackie use the Tip of the jack as the Send, and the Sleeve as the Return- so the Tip needs to wire to the Input side of the LA4 strip, and the Ring wires to the Output.

    Hope you get it sorted!

    :cool:

    AD
     
  8. KB

    KB Guest

    Thanks AD
     

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