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Distortion question

Discussion in 'Electronic Design' started by John - KD5YI, Mar 10, 2011.

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  1. John - KD5YI

    John - KD5YI Guest

    Is less than 1% THD for a preamp considered good, average, bad?

    Gain is 40dBV, frequency 20-20k, Rin~130k, Rout=3.9k

  2. John - KD5YI

    John - KD5YI Guest

    I meant less than .1% (sorry)

  3. tm

    tm Guest

  4. Phil Allison

    Phil Allison Guest

    "John - KD5YI
    ** Gain is only ever " dB ".

    0.1% at what level and frequency ?

    If several volts and falling at lower levels, its perfectly OK for most jobs
    in audio.

    But using budget op-amps like the NE5534 or NE5532 will get you down to
    around 0.002% easily.

    ..... Phil
  5. John - KD5YI

    John - KD5YI Guest

    Ok, thanks, Phil.

    Input is 5mV, output is .5V, frequency .8dB down at 20kHz and flat to 20kHz.

    Yes, I know I can use those OAs for a super amplifier. I just wanted to
    see if I could put a two-transistor amp together myself. And, I just
    didn't want it to be crap.

    Thanks again,
  6. John - KD5YI

    John - KD5YI Guest

    On 3/9/2011 9:44 PM, Phil Allison wrote:


    Input is 5mV, output is .5V, frequency .8dB down at 20Hz and flat to
    20kHz. ^^^^


  7. Phil Allison

    Phil Allison Guest

    "John - KD5YI"

    ** Millions of phono pre-amps were made with 2 BJTs in a feedback pair with
    around 0.1% THD.

    I use a simple, 6 transistor " discrete op-amp " stage that easily out
    performs the NE5532. The secret is in using beta matched NPN and PNP
    devices - still not possible on the same chip AFAIK.

    ..... Phil
  8. BAD.

    It should be an order of magnitude lower at the very least.
  9. John - KD5YI

    John - KD5YI Guest

    Okay, then. I don't feel so bad with what I have.

    But, I'm going to get a few of those OAs you mentioned. They sure look good.

    Thanks, Phil.


  10. If you only buy onesey twoseys they are expensive. If you are going to
    pay a premium anyway, you should buy one of the even better than he
    mentions jobs out there. I mean if it is $3 each or $5 each (or even
    $15)for the 10X improvement, I'd get the good (better) one.

    The AD8066 or the OPA636 or the OPA637

    try this:

    Looks like exactly what I need.

    I'll do it a bit differently though. I work with conduction cooling
    designs all day. It will be fun to miniaturize this even further.
    Very nice, clean design.
  11. John - KD5YI

    John - KD5YI Guest

    About $1US in qty of one for a dual device. That's pretty inexpensive in
    my opinion.

  12. Not for Burr-Brown, dingledorf!

    If you are wired that fucking tight on that small a bit of cash for a
    hobby project, you should invest in suicide kits.

    Buy a nice (the big, whole house type)40kV Kerosene heater starter
    transformer and use yourself to test it. Jeez.
  13. John - KD5YI

    John - KD5YI Guest

    Ah! I didn't recognize you, Archie (Dimbulb, AlwaysWrong, CarperCrawler,
    NymNuts, etc).

    What about Burr-Brown? The subject IC was the NE5532 that Phil suggested
    and I said I would get some.

    And you said "If you only buy onesey twoseys they are expensive."

    And I said...

    Well, you stupid shit-for-brains, why should I try to explain anything
    to you? It won't do any good. I thought for a while that you had at
    least a modicum of intelligence, but you proved me wrong.

    Kiss off, MF.

  14. The ultimate data sheet (in a certain way)...

  15. No. The subject was distortion, idiot.
    Poor baby. Too wussified to spell out your cuss thoughts.

    You say Kiss off, MF to me and I say **** off, you pissy, uneducated

    I handed you the keys to the headphone amp castle and you are too
    goddamned stupid to have enough of a clue to even know what to do with

    Bask in your stupidity, dipshit.
  16. SoothSayer

    SoothSayer Guest

    TI has chips ten times better at under a buck each. That ne5532 chip
    is the LAST chip you should choose for this application.

    The link I posted has characterizations of each. DAmn near any a
    person with half a brain would choose. The 5532 is way down at the
    bottom of the pile.
  17. John - KD5YI

    John - KD5YI Guest

    Interesting! The OPA637 is $24.21 in single quantities.

    Wow, what a deal, SFB (Shit-For-Brains). God, what a dolt.
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