Forum Rule: Always post complete source code & details to reproduce any issue!
Page 2 of 2 FirstFirst 1 2
Results 26 to 32 of 32

Thread: Hydrophone amplifier and sampling

  1. #26
    Senior Member
    Join Date
    Jul 2020
    Posts
    913
    Quote Originally Posted by WMXZ View Post
    The 5.1 nV/sqrt(Hz) voltage noise is acceptable for most LF application. Obviously, the good old time with sub-nV/sqrt(Hz) FETs are gone.
    Well there's still:
    https://audioxpress.com/news/linear-...n-channel-jfet

  2. #27
    Senior Member
    Join Date
    Jul 2014
    Posts
    3,120
    Quote Originally Posted by MarkT View Post
    And it seems that https://shop.micross.com/ sells these good old stuff online (e.g. DPAD protection diodes)

    Worthwhile to see http://www.linearsystems.com/lsdata/...9_App_Note.pdf

    Anyhow, I'm happy to see that Linear reintroduced these components again a year ago.

  3. #28
    Member
    Join Date
    Sep 2014
    Location
    South Dundas, Ontario, Canada
    Posts
    43
    The OP has an interesting project going that I'd like to learn from.


    In an AudioXpress (April 2007) edition, Dennis Colin had a project that used a couple of LSK389 in parallel whose output was fed to an AD797AN opamp. He claims around a 1nV/sqrt(hz) referred input RMS noise performance. Later (Sept. 2007) he published an RIAA preamp using a similar (very low noise) topology.
    Another diy'er claimed that Colin's design could be improved by using a very low noise DC power supply as the circuit hasn't got super high power supply noise rejection. I'm not sure if these 'tweaks' are noticeable in actual use, as some of these ideas end up in specmanship debates.


    Peter.

  4. #29
    Im really loving the discussion going on. Thanks so much all! Im learning a ton. Going to be building it on the bench this afternoon, will post some pictures and results soon.

  5. #30
    Senior Member
    Join Date
    Jul 2014
    Posts
    3,120
    Quote Originally Posted by KOC62 View Post
    In an AudioXpress (April 2007) edition, Dennis Colin had a project that used a couple of LSK389 in parallel whose output was fed to an AD797AN opamp.
    For the record
    https://audioxpress.com/assets/uploa.../colin2993.pdf

  6. #31
    Click image for larger version. 

Name:	amp.jpg 
Views:	16 
Size:	146.2 KB 
ID:	23675

    First version I built was some air wired hot garbage. This is the second that I just threw on a breadboard. Signal is weak and i think I am picking up a lot of noise from my cheap bi-polar voltage reuglator. Need to replace it and put a low pass filter before for the HF noise I seem to be picking up (maybe the supply maybe something else). Going to try to make more progress on it tomorrow hopefully.

  7. #32
    Senior Member
    Join Date
    Jul 2014
    Posts
    3,120
    IMHO, you will never get a realistic performance picture without a solid soldered setup (best is pcb or veroboard)
    Then measurements should be made in a tin-box to shield electric fields that couple into wires.
    A fully differential setup will also help against external interference.
    Obviously, Only 1 power (either PC or external (e.g. battery)) is beneficial to reduce risk of 50 HZ ground loop.

Posting Permissions

  • You may not post new threads
  • You may not post replies
  • You may not post attachments
  • You may not edit your posts
  •