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Capacitor/Condenser Microphones

Discussion in 'Electronic Design' started by Jim Thompson, Nov 6, 2004.

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  1. Jim Thompson

    Jim Thompson Guest

    Didn't some old capacitor/condenser microphones use RF oscillation?

    I seem to vaguely recall such schemes, but my surfing has come up

    Does anyone have some links?


    ...Jim Thompson
  2. Don Pearce

    Don Pearce Guest

    Sennheiser make RF-based microphones. The MKH range is what you want.

    Pearce Consulting
  3. Sennheiser used RF biasing for some of their condenser mics. Don't know of any
    others who did it though. How do I know? Because if the screening was anything
    but perfect they, used to beat with harmonics of the bias oscillators in tape
    recorders and make a right noise.

    No links but you know where to look now.

  4. "Jim Thompson" wrote ...
    Yes, I seem to recall that some early designs used RF, but likely
    nothing in the last 50 years.
    There are some microphone historians that may know over
    I once thought about making a "direct digital" mic by using
    a condenser mic capsule in an RF oscillator circuit and a
    high-speed freq counter to generate the digital samples.
  5. I'm *pretty* sure they still make them. Mainly because they sound great.


    I got lots of hits on Google with: rf condenser -interference -wireless
    (because many sites mention "RF interference" and/or wireless mics)

    (If my previous posting didn't get cancelled properly, ignore it!)
  7. Joerg

    Joerg Guest

    Hi Richard,
    How can you cancel a post to an unmoderated newsgroup? Just curious.

    Regards, Joerg
  8. Canceling a message (only your own, of course!) is a
    fundamental part of Usenet and the NNTP protocol.

    How it is implemented is dependent on which news-reader
    application you are using. I use MS Outlook Express and the
    function is found in the menu bar under "Message". In the
    drop-down menu is a selection for "Cancel Message"

    Note, however, that because of the speed of the modern
    internet infrastructure, your Usenet message may have
    already been forwarded to hundreds (thousands?) of news
    servers and may have already be read/downloaded by
    thousands of readers before the cancel message can go
    out and do its thing. Usenet was a "store-n-forward" or
    a kind of "peer-to-peer" sharing protocol long before
    Napster, et. al. came along. Because of that, cancelling
    a message is a rather unreliable exercise.
  9. OK, lessee-
  10. Guy Macon

    Guy Macon Guest

    Send a post using this syntax:


    Subject: cmsg cancel <Xqbjd.5537$>
    Message-ID: <cancel.Xqbjd.5537$>
    Control: cancel <Xqbjd.5537$>
    References: <Xqbjd.5537$>
    Supersedes: <Xqbjd.5537$>
    X-No-Archive: Yes

    cancel <Xqbjd.5537$>



    Here is a template, ready for you to enter your info:

    Subject: cmsg cancel <>
    Message-ID: <cancel.>
    Control: cancel <>
    References: <>
    Supersedes: <>
    X-No-Archive: Yes

    cancel <>
  11. I saw it at 2:07pm PST. My newsreader says that you
    posted your message at 2:02 But the timestamps are
    not particularly reliable, either IME.
  12. BFoelsch

    BFoelsch Guest

    I have used quite a few old condenser mikes, but I think the only OLD ones
    that used an RF oscillator/detector/discriminator were the Stevens Tru-Sonic
    units, about 1949-1950.
    The most popular of the line was the Stevens C-2S, which was used with the
    OD-4 oscillator demodulator unit.

    Kind of a counter-intuitive setup, the OD-4 contained a crystal oscillator,
    and the microphone head contained the capacity element and a small inductor.
    The oscillator ran of course at a fixed frequency, but the microphone proper
    was part of a discriminator circuit. Microphones were tremendous, sound
    wise, but a real pain otherwise. Because everything was tuned, the mike and
    the O/D unit needed matching serial numbers, and cable damage was generally
    catastrophic, as the cable capacitance was part of the discriminator

    I don't have a link, but I do have a schematic and specs here.

    Other than that, I don't know of any other mikes that used RF. By far the
    vast majority just used a DC polarized capacitor element with an amplifier
    in the mike head.
  13. Or just click the cancel button on the newsreader.

    In both cases hope no one read it first, which they will have done.

  14. Tim Wescott

    Tim Wescott Guest

    Whuffo you doing this?

    If it's of interest QST ran a couple of articles a while back on home
    brewing your own condenser mics, but they use HV DC and FET preamps to
    extract the signal. Pretty clever -- the author was claiming high audio
    quality from aluminum foil and other household items, but then it always
    sounds better when you do it yourself...
  15. Jim Thompson

    Jim Thompson Guest

    Think micro-microphones ;-)

    ...Jim Thompson
  16. Tim Williams

    Tim Williams Guest

    Not only that but most servers don't honor the cancellation either,
    something known as Dave the Resurrector I recall...

  17. Which only works on your own messages. You can also cancel
    others messages, but it is a bit more work. Typically the work
    of automated cancel-bots. I have once written one (revartson)
    for a dutch newsgroup, with permission of 99% of the group.
    Dangerous tool.
    Yes, you need to be quick ;)
  18. You can cancel others' messages?

    I vote you for group moderator.

  19. Yes, no problem.
    Thanks for the compliment but no thanks. I prefer all the
    shit that comes with the package. Personal kill-files are
    more than adequate. The Breitbart index is useless for
    cancel bots. Nocem is better, but still useless, imo.
    Freedom of speach is more important, even if someone replies
    to all postings with 'do you want fries with that'.
  20. Fascinating!

    I clicked cancel about four seconds after I clicked "send"!

    Well, maybe ten.

    The thread isn't up at google yet, but it's only been a few

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