Mr. Haelscheir
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This is a follow-up to https://www.audiosciencereview.com/...hones-with-motu-m2-and-rew.49384/post-1783062 (post #6) where I identified limitations with the off-the-shelf RØDE VXLR Pro and VXLR+ adapters for converting 48V Phantom Power to plug-in-power: the VXLR Pro incurs low noise, but suffers from increasing third-order harmonic distortion in the bass from the transformer or whatever it is using to convert from unbalanced to balanced, while the VXLR+ while having excellent distortion performance incurs some kind of common noise hump, whether or not this is being picked up internally by the MOTU M2 when in unbalanced operation or is coming from the use of Zener diodes to do the conversion. I have also been picking up significant mains noise and its respective harmonics which is mitigated with shielding, though said shielding was implemented on different capsules for which I had been encountering too much second-order distortion perhaps due to my not supplying the optimum bias voltage and load impedance.
I lately came across the "Using a separate bias supply with a split load resistance" section under https://diymics.com/how-to-use-elec...balanced-input-that-provides-phantom-power-pp which showed a fairly simple way to get a balanced signal out of an electret condenser microphone (ECM) without a transformer while providing the correct bias voltage and load impedance. Given this, I am looking for feedback on the following wiring schematic for my upcoming in-ear microphones:
I lately came across the "Using a separate bias supply with a split load resistance" section under https://diymics.com/how-to-use-elec...balanced-input-that-provides-phantom-power-pp which showed a fairly simple way to get a balanced signal out of an electret condenser microphone (ECM) without a transformer while providing the correct bias voltage and load impedance. Given this, I am looking for feedback on the following wiring schematic for my upcoming in-ear microphones:
- I intend on connecting the 0.5*R_L (in this case, 1.1 kΩ) resistors as close as possible to the capsule, maybe even as precision SMD resistors soldered directly to the back of the 8 mm or 9.7 mm capsule so it fits nearly within the custom in-ear mount.
- Regarding shielding, I've seen https://www.audiosciencereview.com/...o-wire-an-electret-microphone-properly.26912/, whereby this would necessarily be following Configuration #3 since I cannot connect the ECM's ground terminal directly to ground in this split load resistance design. I might be able to short the ECM capsule's case to the shielding.
- For ergonomics, I would have a thinner (in order to minimize compromising the seal of on-head headphone measurements) balanced and shielded wire running from the in-ear mic to a support necklace or strap to which I would mount the bias voltage rechargeable batteries (in this case, 3 V). Here, I would like feedback on whether shielding is necessary for the DC connection from the rechargeable battery around my neck back up to the in-ear mic; if anything, I might as well use a shield to transmit the ground connection for the battery. I am also supposing that it wouldn't be a good idea to have the DC connection bundled within the same shielding as the balanced pair.
- From the support necklace/strap, I would then splice the thinner balanced and shielded connections with a regular XLR run, say, about 6' in length to reach my audio interface and accommodate rotating on a swivel chair when taking HRTF measurements.
- Within the male XLR connector's housing, I would have inline electrolytic capacitors to isolate the DC bias from the audio interface for which the 48V Phantom Power will be kept OFF.
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