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Re: Preamp design/Capsules/H2 - was Odd MiniDisc problem when using Mic. input

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  • picnet2
    Hi, Thank you :) - A recent post covered the modification of the Edirol CS-15 which I modified to an MS mic - the result wasnt brilliant due to the method used
    Message 1 of 20 , Jul 1, 2009
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      Hi,
      Thank you :) - A recent post covered the modification of the Edirol CS-15 which I modified to an MS mic - the result wasnt brilliant due to the method used with the Figure 8. I suspect one of the lobes is more responsive than the other throwing out the stereo field. http://www.urlme.net/blog/?p=918 has some recordings.

      --- In micbuilders@yahoogroups.com, Michael Chang <m.chang@...> wrote:
      >
      > Wow, Mike, you've done a ton of work that I must go through carefully.
      > Funny how days of work can be summarized in a few sentences that a reader
      > can skim over but not develop any felt significance until it's read many
      > times over.
      >
      > Your results are interesting. I imagine the cardioid polar pattern is
      > responsible for additional phase funnies when two are used as Figure-8.

      I think it turned out to be a couple of spaced cardioids - Ive also tried two diaphragm's connected to the same FET and also removing the acoustic material from the electret back plate. The later giving the best figure 8 pattern - but the capsule/mic case (=tube) give a strong resonance around 3kHz. I since switched to space omni's binaural rigs and spheres.. Ive avoided the use of amplifiers to keep things simple - although perhaps a differential FET amp based on 3 fets would actually work better for the double capsule version. Something Ill eventually get back to once my current quest for a decent sounding hydrophone is complete.

      > One limitation will be coverage angle with the Blumlein configuration. I'm
      > considering a Pseudo-Blumlein using 6 capsules configured as a Double-MS,
      > in other words, two MS, paired back-to-back, but wired out of phase with
      > the rear-side mics angled 120 degrees (instead of true Fig-8, 180). This
      > can be done with 2 differential amplifiers (to keep it simple) if I can get
      > it to work with parallel capsules FETs at the input stage. One advantage
      > will be flexibility: Switchable configurations from basic patterns to
      > Blumlein, MS, or any in-between combination. The possibilities are endless
      > if the capsules are mounted in such a way so they can be mechanically
      > moveable individually (Sony's ECM-MS957 sort of does this; you can rotate
      > the capsule head to allow sound pickup from the top or side for orientation
      > flexibility).
      >
      > My goal is to make an amplified stereo microphone with line level outputs
      > hopefully without coupling capacitors (personal fetish; never liked caps).
      > Powering is planned to be internal through a couple of 9V batteries.

      Sounds good, keep us posted. - Without the use of caps how do you stop the effects of dc bias on the signal - rely on the recorder decoupling?

      BR,
      Mike.
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