AES3 / AES42 Microphone System, CNC case

aShure

Member
2016-02-19 2:27 am
Hey there! :)

I sketched this concept for a digital AES42 mic. It's quite small to be portable, getting pretty tight on the PCB. I try to construct everything to be CNC milled or turned.

Fanatone Violet Microphone Case 2 v4 rt 2.jpg
Fanatone Violet Microphone Case 2 v4 rt bot tagged.jpg

Not yet set on the capsule, I sketched some ideas for large diaphragm capsules. Here's one with four rectangular membranes.

FAT Capsule R v3.png
FAT Capsule R v2 cut2.png

l4KhQflrjybDKxt7y.gif


I still need to read about those half deep hole patterns - these renders are just some rough sketches.

I will probably just use a MEMS mic with digital output fed into the AES3 encoder to gain some experience with the case shape and general handling.
For such large diaphragm capsules like the ones displayed the enclosure will probably be way too tight to let it breath and not cause lots of parasitic reflections and resonances.


26FPvVaN6lnfGoOoE.gif


The body contains the buffer, preamp, ADC (PCM42xx, e.g. PCM4201), AES3 encoder (DIT4096/DIT4192), 50V DC boost converter for capsule bias (LT8330) and some voltage regulators to convert the DPP (10V) into suitable levels.

Fanatone Violet Microphone Case 2 v5 - PCB draft.png

The local clock source for the AES3 encoder and ADC (Ti PCM4201) will be a 24.576 Xtal. Can I hook the xtal up to the clock inputs directly or is their impedance too low? I couldn't find any specific information about the load in the datasheets, but I know that the evaluation boards for the Ti ADCs always use a buffer (I think it was a hex inverter) in between, but those boards have multiple clock sources and switchable clock inputs where they need to decouple the xtals. If possible I would like to leave out a buffer.

Cheers

Shu
 

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