Modding an Mixing Desk

Discussion in 'General Electronics Chat' started by suchenderxxx, Jun 29, 2012.

  1. suchenderxxx

    Thread Starter New Member

    Jun 29, 2012
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    hello guys,

    i am new to this forum and i wanna say hello to all of you.

    I have bought an studiomaster 16-4 Mixing Desk and cleaned it and fixed some broken solderings. Now i wanne see if i can improve the soundquality of this board with changing the opamps or recapping it. But im new in such electric things, so i wann hear your opinions on this. The last time i openede the Desk i believe i saw this build in opamps in the desk: 741 and the 742. What would be a good replacement and how about the difference it will make? This Desk is ca. 25 years old and inside looks very good, no broken caps or fluid comming out of them, also this desk was modded with line outputs in the year 1990 from an musicshop here in germany, there was an sticker inside.

    what are your thoughts? what would be a step up in terms of soundquality?

    thanks and regards
     
  2. t06afre

    AAC Fanatic!

    May 11, 2009
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    In such old equipment. I would have changed all electrolytic caps. The 741 type opamp was (and sadly still is) a standard type opamp. Almost any modern opamp with the same pin configuration and supply range will do better than a 741 opamp. Perhaps OPA134 can be a good replacement. For the 742 I do not think that was any opamp. Just to be sure can you post some close up pictures of the board
     
  3. suchenderxxx

    Thread Starter New Member

    Jun 29, 2012
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    i will post pics in the evening.

    i have read that the opamp 5532 would be a replacement? i want improvement in soundquality. the capacitors look good to me cosmetically, like new... if i change the capacitors should i replace them with the same capacity or bigger ones? and should i change the caps at the psu also? is it dangerous if the powercord is not plugged? is there any voltage still in the psu?

    which specs are the one to look for getting a compatible replacement?
     
  4. kubeek

    AAC Fanatic!

    Sep 20, 2005
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    Electrolytic caps dry out over time, so I would change all of them for the same capacitance and same or higher voltage rating. There should be no charge left after you turn it off, but if you want to be sure just short the caps with a screwdriver or something.
     
  5. suchenderxxx

    Thread Starter New Member

    Jun 29, 2012
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    so i should also change the caps in or at the psu?

    this sounds like much work to do... but i think it must be done.
     
  6. crutschow

    Expert

    Mar 14, 2008
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    The 5532 is a low-noise op amp designed for audio applications, so it should work well as a replacement. The main difference in making such a replacement would be the reduction of the low-level white noise (hiss). But it is a dual op amp, so won't be a pin-for-pin replacement of a 741.
     
  7. suchenderxxx

    Thread Starter New Member

    Jun 29, 2012
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    what about the ne 5534 this is an single opamp. i found a thread where someone posted that this is a good replacement. but im not good in reading schematics so i wanna know your scientists opinion on these. in a music forum they told me that i can get problems with the psu cause this new opamps need more voltage... is there anything to do so that the psu can handle this opamps? i also found in the same thread that an opa 134 should work in place of the 741, is it pin compatible to the old opamp?
     
  8. t06afre

    AAC Fanatic!

    May 11, 2009
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    Good thing you asked. APA 134 will be combatible with 741 if the offset adjust function are not used for the 741 type opamp
     
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