Tweaker's Asylum

• Input Bias Currents djk 03:32:58 06/12/01 (3)
  In Reply to: Opamp Replacement ? posted by Eli Duttman on June 11, 2001 at 15:15:38:

  If I remember correctly the caps are ~.1µF and the resistors ~100K.You will have to use a bi-fet op-amp.The OPA2604 sounds quite good in this circuit.
  
  

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  • Re: Input Bias Currents Eli Duttman 14:42:16 06/12/01 (2)
    In Reply to: Input Bias Currents posted by djk on June 12, 2001 at 03:32:58:

    Thanks for the "heads up". The TL072 is Bi-FET; the replacement will have to be Bi-FET too. Decision made, the Burr-Brown OPA2604 will be the replacement. The change can be tried as soon as the IC arrives. The unit has had a socket for the opamp IC from day 1 (that's the way the kit shipped).
    
    Eli D.
    
    

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    • Re: Input Bias Currents Lew 17:25:50 06/14/01 (1)
      In Reply to: Re: Input Bias Currents posted by Eli Duttman on June 12, 2001 at 14:42:16:

      What's wrong with the TL072?
      
      

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      • Nothing ! djk 05:33:43 06/16/01 (0)
        In Reply to: Re: Input Bias Currents posted by Lew on June 14, 2001 at 17:25:50:

        > > What's wrong with the TL072? < < Nothing.They sound better than LF353s.An OPA2604 blows them away.A TL072 was SOTA in 1978.
        
        
        

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• Re: Opamp Replacement ? chiggy 16:05:21 06/11/01 (2)
  In Reply to: Opamp Replacement ? posted by Eli Duttman on June 11, 2001 at 15:15:38:

  Hello Eli,

  I'm pretty sure the pinout is the same for the dual FET TL072 and my suggestions - OPA2604, OPA2132, OPA2134 and LM6172 - these should sound better than the 72 but may need some bypass caps to prevent oscillation.

  Not to sure about the unity gain part with these opamps - you may need to change a few resistors and caps; I'll leave that to the experts and the product data sheets.

  Good luck,
  chiggy
  
  

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  • Re: Opamp Replacement ? romaxim 18:11:21 06/11/01 (0)
    In Reply to: Re: Opamp Replacement ? posted by chiggy on June 11, 2001 at 16:05:21:

    Analog Device OP285 sounds very good, direct replacement without oscillation problems. According to my experience, the best choice is Burr-Brown OPA 2604 (also direct replacement), but needs pretty long break-in.
    Of cource, proper bypass and grounding is always very important (see Analog Devices Application Note AN-202, to be found on their website).
    Good luck!
    Max
    
    
    
    

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  • addendum... chiggy 16:19:05 06/11/01 (0)
    In Reply to: Re: Opamp Replacement ? posted by chiggy on June 11, 2001 at 16:05:21:

    One more thing - if you don't have too many op-amps to replace, I suggest you solder in a decent socket and experiment to see what you like. From my experience with op-amps, I can say each flavor will have a sound all it's own - it's like SS tube rolling in a 00's sort of way.

    regards,
    chiggy
    
    

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