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NE5532 vs. TL072 Whichone is quieter?

Discussion in 'General Electronics Chat' started by drrogla, Apr 20, 2005.

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NE5532 vs. TL072 Whichone is quieter?

  1. NE5532

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  2. TL072

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  3. No difference

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  1. drrogla

    drrogla New Member

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    Does anyone have any experience on whichone is better suited for audio aplications (preamp). Just need something with wery low noise!!!
     
  2. Nigel Goodwin

    Nigel Goodwin Super Moderator Most Helpful Member

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    The NE5532 series are designed specifically for audio applications, so are probably better for noise performance. I've just replaced two 741's in the mike preamps of a PA amp with TL071's and I can't really tell any difference in noise levels? - and I expected them to be far quieter!.

    You might also consider the more modern Burr Brown devices?, something like OPA134? - as I recall from memory (having just got back from the pub!).
     
  3. chemelec

    chemelec Well-Known Member

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    The Op-Amp is only Part of the Problem.

    Regular Resistors can create More Noise than the Amplifier, Especially Higher Values.

    Buy Some Lower Noise Resistors.

    Gary
     
  4. dave

    Dave New Member

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  5. audioguru

    audioguru Well-Known Member Most Helpful Member

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    The bipolar transistor inputs of the NE5532 draw input current and are completely different from the JFET inputs of the TL072 that don't have any input current. Therefore if the source impedance is very low (spec'd at 20 ohms), the NE5532 is 3 times quieter.
    But when the source impedance is about 18.5k ohms, they have equal noise levels because the input current noise adds to the input voltage noise of the NE5532. With a source impedance greater than about 18.5k, the TL072 is quieter. You will often see a NE5532 as a phonograph cartridge, tape head or microphone preamp with a whopping big input coupling capacitor that takes nearly forever to charge. The low impedance of the big input cap keeps the input current noise low.

    Having bipolar transistors on its input, the NE5532 has "popcorn" noise below 30Hz while the TL072 has much less.
    The NE5532 has back-to-back protection diodes on its inputs that mess-up many circuits and it draws much more supply current than a TL072.

    Do you want to see on a 'scope and hear something kinda cool?
    If a TL072 is used as a non-inverting amp, if its input is overdriven to near 2V above its negative supply, it suddenly inverts and produces a positive output! Most JFET-input opamps do that. :lol:

    As Nigel says, there are many more modern opamps available with much less noise but they cost much more.
     
  6. Nigel Goodwin

    Nigel Goodwin Super Moderator Most Helpful Member

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    Yes, I'm very aware of that - but I would still have expected the 741 to be contributing much more noise than the rest of the components (particularly as there aren't many of them).
     
  7. audioguru

    audioguru Well-Known Member Most Helpful Member

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    Hi Nigel,
    You replaced 741's in the preamp with TL071's, but still had a noisy old 741 in the mixer, didn't you?
    If you turn down the mixer input control and the noise goes away, you can't assume that the noise is created ahead of the input control because it presents a low impedance to the input of the 741 in the mixer, reducing its input current noise. :lol:
     
  8. Nigel Goodwin

    Nigel Goodwin Super Moderator Most Helpful Member

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    The 741 in the mixer is a virtual earth mixer, turning the input controls can't affect it - that's the point of having a mixer!. Also the tone controls on the front end affect the noise levels, proving it's coming from ahead of the controls.
     
  9. audioguru

    audioguru Well-Known Member Most Helpful Member

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    Hi Nigel,
    Yeah, the TL072 is cheap and ain't perfect. Analog Devices and Linear Technology make some extremely low-noise opamps. Judging by their very high price, their yield must be low. I can picture the production line where they all cheer each week or two when they produce one IC out of thousands that actually is very low noise! I'd like to get the ones they throw away. :lol:
     
  10. Nigel Goodwin

    Nigel Goodwin Super Moderator Most Helpful Member

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    I think they just keep the price high because it's a premium product, and not aimed at cheap equipment - assuming they have failures, they probably just label them as something else :lol:
     
  11. audioguru

    audioguru Well-Known Member Most Helpful Member

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    A factory here made way too much canned tuna fish. They couldn't sell it for years so re-labeled it as cat food and sold it overseas. It came back here re-labeled again as tuna fish. People who bought it found it to be putrid rotten.
     
  12. drrogla

    drrogla New Member

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    Does that mean that they are better suited for input of phono preamp-type circuts??
     
  13. drrogla

    drrogla New Member

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    and about the resistors: I was going to use good quality resistors...
     

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