OPAMPS TL 084 vs. OPA 4132

Discussion in 'DIY Pro Audio Forum' started by JRE Productions, Aug 11, 2003.

  1. I'm thinking of upgrading an EQ that uses the TL 084 quad opamp through out. It is pin for pin compatible with the Bur Brown OPA 4132 unit.

    Will there be a noticeable difference in these opamps?

    The Eq uses 1 portion of each amp at each of its 10 bands, plus at the input and I think output.

    What do ya'll think?

    Joe
     
  2. Bear's Gone Fission

    Bear's Gone Fission

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    Two quick things to watch for: what's the difference in current draw (maybe not a factor in a small piece w/ only a few chips, but potentially a big issue is something like a console) and is the replacement unity-gain stable. I don't really know the TL084, or that specific Burr Brown, so beyond that I'm of not much help.

    Bear
     
  3. cuelist

    cuelist Guest

    Probably not if you ask me, but I am not your typical 'golden ears'...


    It really depends on how this eq is designed. I am suspecting these TL084's are used as gyrators, one per band. In that case, swapping them for something more 'upmarket' will probably not make any audiable difference.

    However, if it is a stupid design where the signal passes through ten consecutive stages then it may make some difference.

    In that case, you need to consider that circuitry around the opamps, what impedance level they are running at and so on. How hard are the TL084's driven?

    Without a schematic or at least a good description of the circuit it is almost impossible to give solid advice.
     
  4. Thanks, It is a UREI 533 10 band EQ. YOu can find the schematic at the JBL site.

    Basically though, The input passes through the first quadrant of the first opamp. Then each of tens bands get there boost or cut by passing through a quadrant of a opamp. Then the final make up gain goes through the last quadrant. 5 opamps total.

    The burr browns are close enough in spec that tecnically there should not be a problem. The burr brown chips are supposedly quieter and a little more robust sounding.

    Joe
     
  5. Kev

    Kev Guest

    As Bear said,
    as this is only a single unit power supply issues should be OK.
    Replace the IC with a socket and try a few of the pin compatible ic's and see what you hear.

    Beware of the chance for an oscillation and be prepared to solder a cap to control it.

    Lets us know you results.
     
  6. gyraf

    gyraf Guest

    The TL074 is a low-noise version of the TL084, so this would be the logical upgrade. Or you may want to try the MC33079, a quad version of the LM833. I've had very good results with that for eq's. But be aware of possible supply line instabilities.

    Jakob E.
     
  7. cuelist

    cuelist Guest

    Found a schematic here:

    http://www.waltzingbear.com/Schematics/Urei/533.htm

    From this schematic I'd say that IC1, 4 and 5 would be worth replacing.

    The others work as gyrators (inductor simulators) and should not make any difference between TL084 and OPA4132.
     
  8. bauman

    bauman Guest

    Last edited by a moderator: Mar 31, 2014
  9. Fabio,

    THanks for the links. THye are sending me the 2084 samples overnite! Pretty cool. Actaull, I think they are sending enough for the whole job, which is 5.

    I'll update you guys soon.

    Joe
     
  10. adamasd

    adamasd Guest

    Why not jsut use the TLO64, it is the low noise versoin of the TLOXX series. The TLO74 is said to be a low noise TLO84, but the difference is not much, the TLO64 is much quieter. I would expect it to be plenty quiet for this use. Generaly if something uses TLO84s there are going to be other souces of noise in the circuit other then noisey opamps, like the power supply and many other things, an upgrade from the standard electrolytic caps in the power supply would help, not to mention the caps could be getting old and dieing. Good electrolytics generaly have a life span of 25 years or so, but i have seen ones that pretty much stated they had a 1 year life span right on them. Also if the resistors are carbon comp they can be a source of noise, they also tend to drift with time. The 533 is not to old, but still could be carbon comp. The power supply has a pretty hefty chunk of filtering, but I would replace those electrolytics. The rectifier might worth looking into also, It uses plain old 1N4003 didoes, which can be a source of noise. they can be updated to U4003 or even FREDs if you want to spend some money. Read the recent post on rectifiers, it has alot of good information. 78XX and 79XX series regulators are pretty noisey also, There are much better choices. The power supply does have a good chunk of filtering, but the power supply as a whole could be improved. I would replace those electrolytics first, that could be a big source of noise in a 20 year old EQ. Then do the opamps and maybe the rectifier diodes. I would just repace the power supply if it is on its own board, if it is not, I would replace the electrolytics and diodes at a minimum.

    Adam
     
  11. cuelist

    cuelist Guest

    I may remember wrong but I was always under impression that the TL06x was the low power version.

    But you have actually tested the TL064 and found it to be more quiet?
     
  12. McQ

    McQ Guest

    The TL06X is the low(er) power version. The TL06X noise levels are too high for serious audio (particularly if you want stuff like gain)!
     
  13. ssltech

    ssltech Guest

    Not wishing to jump on that post excessively, but every time someons brings something to me complaining that it "sounds like there's a bad cap in it" it ends up boing noise from some other source. -Whenever there really is a bad electrolytic, then bring it to me saying "there's no bass"...

    My own uses of TL06x opamps (battery powered stuff) have yeilded some pretty awful sound... I've always got better results from ) 07x. -Local ceramic filtering has always gotten me to the point where even 78xx and 79xx regulator noise has been a complete non-issue. -The usual thing electrolytics have given me real noise problems is 120-cycle (or 100-cycle in Europe) hum from an almost totally dried-up reservoir cap...

    -Doesn't the 06x series have a crossover distortion "dead band" on the output stage... this might help keep the current consumption down, perhaps though in a 'silence' condition, a dead output might be mistaken for a quieter output? -Just guessing here, I could be way off.

    Keith
     
  14. Hi All,

    This EQ is not all that noisey to begin with. I just wanted to try some easy and inexpensive upgrades or mods for the heck of it. No real problems exist, but I'm trying to learn the technology.

    The 533 is just another eq. Nothing special, and sometimes thats good. But I thought I would try to put some IRON into it.

    Joe
     
  15. gus

    gus Guest

    I don't like the TL06x for audio. I find I like the LF353 better than the TL072 with effects and amps. I have not tried the LF353 in pro stuff yet.
     
  16. Mark Burnley

    Mark Burnley Guest

    Keith,

    Can this "boing noise" be measured, or do we have to take your word for it?

    [​IMG]

    gus,

    I like the LF351/353's for guitar FX too. Got a drawer full of the blighters. They're slightly less well spec'd than the TL071's, and you don't see them much in pro-audio gear. But I've used them in a bunch of stomp boxes!

    Mark
     
    Last edited by a moderator: Mar 31, 2014
  17. Hi Guys, well I got my TL074 samples today. I opened the unit for the first time just to see that the opamps had already been changed to TL074's by someone else before me!

    I guess that kills another fun project.

    Joe
     
  18. ssltech

    ssltech Guest

    ...sorry... of course this is a typo.

    I meant "Boeing noise" which as we all know is what happens when they re-route the approach path so that 747's have to fly low over your studio.


    [​IMG] [​IMG] :D ;) [​IMG]
    Keith
     
    Last edited by a moderator: Mar 31, 2014