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Re: circuit for active ribbon mic

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  • Mike Rooke
    Pre-amp gain increased, thus something like this:- http://www.urlme.net/blog/?p=2012 Sensitivity matched to the NT1A and 7dB greater than the NT2A s. Low and
    Message 1 of 82 , Mar 22, 2013
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      Pre-amp gain increased, thus something like this:-

      http://www.urlme.net/blog/?p=2012

      Sensitivity matched to the NT1A and 7dB greater than the NT2A's.
      Low and high ends not attended to yet. Probably easier to handle those with digital EQ.

      Wobbly responses due to desk clutter, me, reflections etc in the room.

      I guess that makes it a rather sensitive velocity transducer at least to 5 Khz.

      Outdoor & side by side with the NT2A + NT1A to follow, plus self noise measurements will be attempted....

      BR
      Mike.

      --- In micbuilders@yahoogroups.com, "ricardo" <ricardo@...> wrote:
      >
      > > Using 2 x 2SC3329's with HFE at 580, is there a way to estimate the noise for the simple lifter circuit by the numbers?
      >
      > > - Ive assumed 48V on hot and cold, 6.8K to Collector & Base have the 680R resistor, emitters to ground. I get around 642nV output noise running 1Hz to 20 Khz 20 steps / interval (Octave) in b2spice. 50R between bases simulating the RP40 transducer Is that "about right"? Gain shows in spice as 36.5dB. The transducer is around 11mV/PA, self noise (not anechoic) was measured around 20dBA SPL. I suspect its lower in the anechoic chamber.
      >
      > Your output 642nV is -123.85dBV. With 36.5dB gain, this makes Ein -160.35dBV at the input which is far too good.
      >
      > I expect about 1dB more than the noise of the 50R which is -137.7dBV over 20kHz.
      >
      > The gain of Ribbon.gif is roughly proportional to R1/2 680R. You could adjust these so your mike has the same sensitivity as NT1A, then listen to both for an accurate comparison.
      > __________
      >
      > Excellent blog BTW.
      >
      > I would look at how to conveniently apply EQ digitally rather than mess with the electronics. But the reason your mike has less handling noise than NT2A is probably cos of the bass rolloff .. so don't EQ below 100Hz at LF.
      >
    • Mike Rooke
      Pre-amp gain increased, thus something like this:- http://www.urlme.net/blog/?p=2012 Sensitivity matched to the NT1A and 7dB greater than the NT2A s. Low and
      Message 82 of 82 , Mar 22, 2013
      • 0 Attachment
        Pre-amp gain increased, thus something like this:-

        http://www.urlme.net/blog/?p=2012

        Sensitivity matched to the NT1A and 7dB greater than the NT2A's.
        Low and high ends not attended to yet. Probably easier to handle those with digital EQ.

        Wobbly responses due to desk clutter, me, reflections etc in the room.

        I guess that makes it a rather sensitive velocity transducer at least to 5 Khz.

        Outdoor & side by side with the NT2A + NT1A to follow, plus self noise measurements will be attempted....

        BR
        Mike.

        --- In micbuilders@yahoogroups.com, "ricardo" <ricardo@...> wrote:
        >
        > > Using 2 x 2SC3329's with HFE at 580, is there a way to estimate the noise for the simple lifter circuit by the numbers?
        >
        > > - Ive assumed 48V on hot and cold, 6.8K to Collector & Base have the 680R resistor, emitters to ground. I get around 642nV output noise running 1Hz to 20 Khz 20 steps / interval (Octave) in b2spice. 50R between bases simulating the RP40 transducer Is that "about right"? Gain shows in spice as 36.5dB. The transducer is around 11mV/PA, self noise (not anechoic) was measured around 20dBA SPL. I suspect its lower in the anechoic chamber.
        >
        > Your output 642nV is -123.85dBV. With 36.5dB gain, this makes Ein -160.35dBV at the input which is far too good.
        >
        > I expect about 1dB more than the noise of the 50R which is -137.7dBV over 20kHz.
        >
        > The gain of Ribbon.gif is roughly proportional to R1/2 680R. You could adjust these so your mike has the same sensitivity as NT1A, then listen to both for an accurate comparison.
        > __________
        >
        > Excellent blog BTW.
        >
        > I would look at how to conveniently apply EQ digitally rather than mess with the electronics. But the reason your mike has less handling noise than NT2A is probably cos of the bass rolloff .. so don't EQ below 100Hz at LF.
        >
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