Tweaker's Asylum

• Re: What's a normal one in audio gear look like? Or does it vary? (nt) Steve Eddy 14:16:39 02/03/01 (9)
  In Reply to: What's a normal one in audio gear look like? Or does it vary? (nt) posted by GPB on February 03, 2001 at 12:19:52:

  Most typically they'll be in 8 or 14 pin plastic DIP (Dual Inline Package) packages like this:

  
  
  

  Single and dual opamps will usually be in an 8 pin package and quad opamps will be in 14 pin packages.

  Or they might be in plastic surface mount packages like this:

  
  
  

  Or less typically they may be in TO-5 metal can packages like this:

  
  
  

  se

  
  
  
  
  

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  • Great! Thanks for going to the trouble. One more ? GPB 22:57:28 02/03/01 (1)
    In Reply to: Re: What's a normal one in audio gear look like? Or does it vary? (nt) posted by Steve Eddy on February 03, 2001 at 14:16:39:

    Are these fairly easy to de-solder and install better ones? I've got an itch to do this on my pre/pro that is kind of obsolete already. I suppose I would need the tech manual? Or not?

    It's a Sony EP9ES.

    Thanks!

    -- Greg
    
    

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    • Re: Great! Thanks for going to the trouble. One more ? Steve Eddy 23:19:56 02/03/01 (0)
      In Reply to: Great! Thanks for going to the trouble. One more ? posted by GPB on February 03, 2001 at 22:57:28:

      GBP wrote:

      Are these fairly easy to de-solder and install better ones? I've got an itch to do this on my pre/pro that is kind of obsolete already. I suppose I would need the tech manual? Or not?

      If they're through-hole and not surface mount they can be fairly easily desodered. Can be a bit of a pain removing it intact if you're just using braid or a solder sucker but I wouldn't recommend clipping off the leads since you wouldn't be able to put the original back if you needed to. And yes, the service manual would be a plus to have.

      se

      
      
      
      
      

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  • Re: What's a normal one in audio gear look like? Or does it vary? (nt) Mars 20:26:18 02/03/01 (6)
    In Reply to: Re: What's a normal one in audio gear look like? Or does it vary? (nt) posted by Steve Eddy on February 03, 2001 at 14:16:39:

    Do op amps have class A outputs? Or do they have crossover distortion?

    Thanks,

    Mars
    
    

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    • Class A op-amps Daniel Espley 04:56:31 02/04/01 (4)
      In Reply to: Re: What's a normal one in audio gear look like? Or does it vary? (nt) posted by Mars on February 03, 2001 at 20:26:18:

      It's popular with some to bias op-amps into class A by adding either a resistor or constant current source between the op-amps output and one of the supply rails. I've tried this with a couple of op-amps, but couldn't tell any difference - but then the distortion of modern devices is very low to start with.

      Daniel Espley
      
      

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      • Re: Class A op-amps Mars 16:09:48 02/04/01 (3)
        In Reply to: Class A op-amps posted by Daniel Espley on February 04, 2001 at 04:56:31:

        Thank you for your responses... I have more questions you could help me with that I have always been wondering about...

        I am using an LH0033cj video buffer IC as an audio output buffer. It is a hybrid design and gets fairly hot during operation. Could this mean it is internally biased for class A?

        Second question...
        Is some crossover distortion present with all IC op amps, and if not then why do the best pre-amps use tubes?
        
        

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        • Re: Class A op-amps Werner 03:34:45 02/07/01 (0)
          In Reply to: Re: Class A op-amps posted by Mars on February 04, 2001 at 16:09:48:

          Some opamps have idling currents sufficiently high to classify them
          as deep class AB. You can look at the idle supply current. When that
          it in excess of 10mA you may be lucky, even though this is not
          always indicating class AB.

          A good example is the AD845, which indeed is deep AB, and would
          probably never leave class A for normal audio applications.
          
          TNT Audio Netzine
          
          

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        • Re: Class A op-amps Daniel Espley 08:43:32 02/05/01 (1)
          In Reply to: Re: Class A op-amps posted by Mars on February 04, 2001 at 16:09:48:

          Hi,

          "I am using an LH0033cj video buffer IC as an audio output buffer. It is a hybrid design and gets fairly hot during operation. Could this mean it is internally biased for class A?"

          I don't know anything about the LH0033cj, I'm afraid.

          "Second question...
          Is some crossover distortion present with all IC op amps, and if not then why do the best pre-amps use tubes?"

          They do? Most op-amps specified for audio will run in class AB. But most use huge amounts of negative feedback to drive distortion down to negligible levels. As for tubes, technical specification doesn't really come in to it. Some people just like tubes.

          Dan

          
          
          

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          • Re: Class A op-amps john curl 21:25:37 02/10/01 (0)
            In Reply to: Re: Class A op-amps posted by Daniel Espley on February 05, 2001 at 08:43:32:

            The Lh0033 is a good buffer. It Is not really anything but class A-B. Not bad. Trust your ears. Don't load it with too much.
            
            

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    • Re: What's a normal one in audio gear look like? Or does it vary? (nt) Steve Eddy 23:21:56 02/03/01 (0)
      In Reply to: Re: What's a normal one in audio gear look like? Or does it vary? (nt) posted by Mars on February 03, 2001 at 20:26:18:

      Mars wrote:

      Do op amps have class A outputs? Or do they have crossover distortion?

      Can't think of any IC opamps off the top of my head that are biased in class A, but many are biased in class A/B. The data sheet will often (but not always) indicate output bias.

      se

      
      
      
      
      

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