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Op Amps

Discussion in 'd.i.y.' started by Bigman80, May 19, 2017.

  1. Bigman80

    Bigman80 Member

    Hi all,

    This is my first post so forgive me if it's in the wrong area!!


    Have any of you had any experience with SS3602 Discrete opamps?

    heres a link: http://sparkoslabs.com/product/discrete-op-amp-ss3602/

    I've ordered a couple based on the reviews. The reviews are very complimentary but a few unbiased opinions would be welcome!

    Thanks in advance
     
  2. Julf

    Julf Evil brother of Mark V Shaney

    I guess it all depends on what you want to use them for...
     
  3. S-Man

    S-Man Kinkless Tetrode Admirer

    At least the data sheet is reasonably comprehensive, which is not always the case with these type of things.

    Must admit I would be interested to try them, but not at $80 each. Especially as my favourite opamps on his list are the ones with the worst figures :confused:

    Let us know how you get on, and as Julf says, where they are going to be used and what they are replacing.
     
  4. russel

    russel ./_dazed_and_confused

    LME49724 LME49600 LME49720 LME49860 LME49710 LM4562 OPA1632
    2.1 3 2.5 2.5 2.5 2.7 1.3 all nV sqrt Hz


    I notice he has left some of the op-amps with lower noise off his table, they may be very good and maybe better but I am not sure about super expensive op amps since the ones listed above are a bit too new for recording studios, most of the music you listen to will have been through a 5534 or more likely a 5532 at some point. You can get good results from analog devices or Ti parts for a lot less money.
     
  5. Andrew.B

    Andrew.B pfm Member

    I went though a phase of 'rolling' opamps, and unlike many I was actually using legit parts direct from Ti, etc, not reprinted Chinese spiders, and gave up because I honestly didn't have a clue what I was doing, swapping opamps in and out of random circuits just seemed silly and I had no idea what was going on, and when the hierarchy began to emerge, realised it was a load of audiophool BS.

    The sight of those first discreet opamps, boards stuffed with though hole components with measurements so terrible, hanging off tiny 8 pin sockets was kinda funny though, certainly looked very impressive, great for selling a blurb. Glad they've adopted SMD.
     
  6. davidsrsb

    davidsrsb pfm Member

    Forty years ago there was a real market for discrete opamps, as it was not possible to integrate a decent pnp transistor -709 and 741 were terrible. This went away when Harris introduced their dielectric isolated process with workable pnp devices and since then discrete only made sense when you wanted an unusual feature like high supply voltage.

    I noticed that this model won't work on +/- 5V and has very high input current
     
  7. audiopile

    audiopile pfm Member

    One company that has continued to use (quit successfully) the discrete opamp is Bryston. I suspect that this is one of the reasons they are very reasonable about publishing their schematics (something I appreciate!). Wonder how many attempts are made to order those Bryston op amp numbers from parts suppliers ?
     
  8. Bigman80

    Bigman80 Member

  9. davidsrsb

    davidsrsb pfm Member

    Analog Devices are making fairly cheap parts like the ADA4897-2, with remarkable specs. 1nV/rtHz and 230MHz GBw and only 2.4nV/rtHz at 10Hz. This is enough to compete with unobtanium 2SK170 designs in MC preamplifiers. These make the discrete opamps look a bit limited
     
  10. demotivated

    demotivated pfm Member

    It might be low voltage noise at the expense of highish current noise and therefore not ideal for low impedance inputs, but it is astounding specs - 230MHz gbw in an audio friendly part, wow.

    edit - just read up the datasheet and it's another decade ahead of my electronics experience - amazing.
     
  11. martin clark

    martin clark pinko bodger

    Phenomenal specs are one thing; actually delivering it in-situ can be quite another!

    Implementing really fast/really-quiet opamps takes great finesse in layout and decoupling, and some savvy and test gear to check stability (at the very least). It's why 'rolling' op-amps generally/blindly is a complete crapshoot - most of the reported differences are about differing sensitivities to the implementation it has been plunked into, rather than any measure of opamp 'goodness' (for want of a better description.)

    There are multiple, interacting dimensions at work; picking by datasheet top-trumps is no guide at all - unless you can define which parameters really matter / have some inkling as to which ones the circuit you are playing with is sensitive-to. A short list of examples for the sake of handwaving: the audiophool faves of slew rate and noise, for a start are very rarely good 'picks' (you want the slowest opamp that will do the job well-enough, for all sorts of reasons; and in line-level circuits, noise is usually limited by other issues than any modest op-amp can offer. A subject for another day); PSRR might matter, but PSRR at 10k-100kHz might be more interesting in the circuit you are playing with; and in a filter it might just be CMRR and/or GBW are key parameters above all, depending on filter design...
     
  12. davidsrsb

    davidsrsb pfm Member

    You cannot just drop this AD part in place of a NE5532 in your CD player, you need to consider supply voltage - modern parts are for a +/-5V world or even lower and with 230MHz bandwidth, forget putting it on a single layer board with long tracks and no local decoupling
     
  13. S-Man

    S-Man Kinkless Tetrode Admirer

    Completely agree!!

    And from a subjective viewpoint -IMO the decoupling makes more difference to the sound than changing the opamp. It's difficult to measure any differences when changing decoupling, and of course it's all dependent on the layout.
     
  14. davidsrsb

    davidsrsb pfm Member

    I used to design video amplifiers and tested with a frequency sweep up to 10MHz in the TV line. It was very clear on the test equipment displays how decoupling changes could cause small ripples in the sweep amplitude.
    Applications like DAC IV converters contain high frequencies than video.
     
  15. S-Man

    S-Man Kinkless Tetrode Admirer

    And could you correlate the measurements with picture quality?

    I suspect it will be quite hard to meaure any differences with typical DIY test gear and in a phono stage (which is the op's application).

    BTW Bigman - you should be very careful indeed if you are thinking of using the Sparko with dc coupling as the 1st stage of an MC amp!
     
  16. davidsrsb

    davidsrsb pfm Member

    The human eye is very poor at seeing picture distortions. The specs are set at a level that allowed the BBC to cascade many amplifiers without causing problems.
    Supply decoupling is more likely to affect the regulators than the opamps and the regulators are dealing with wideband rectifier noise
     
  17. Bigman80

    Bigman80 Member

    It's going into the second stage. I am looking for a super quiet Opamp to create the gain in the first stage.
     
  18. Bigman80

    Bigman80 Member

    I'll look into these. Thank you David
     
  19. Julf

    Julf Evil brother of Mark V Shaney

    A discrete one is probably not the best choice for super quiet.
     
  20. Yomanze

    Yomanze pfm Member

    I do find it an interesting phenomenon that there is this assumption that 'discrete is best', but there are some distinct advantages to opamps such as shorter signal paths, better thermal tracking etc. It's sobering indeed to open up some LFD gear & see some of it built around a pair of opamps with a gigantic power supply, not much else, but it's the circuit tuning that makes the difference here.

    Pedja Rogic put it well when designing his chip amp: "It takes some time to understand this simple fact about modern linear power amp chips design: the chip is not the limiting factor. It can be anything. The limit is design around it."
     

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