DC-DC Converter for Multi-Pattern Phantom powered mic.

[Khron]

You might want to consider the Rode route, and have some RC filtering also "downstream" of the pattern switch. It might also lessen the pattern switch "pop", but can't guarantee to what extent. And @RuudNL 's thought of tacking on a 1G resistor from the rear diaphragm to ground (to discharge it when switching to cardioid) might not be a bad idea either.

https://groupdiy.com/threads/why-you-should-never-use-multi-pattern-mics.81157
Since C10 & C13 are basically a short to ground for AC, the pattern switch is not in a high-impedance area, so no such concerns there.

Interesting, I’m not opposed to getting rid of a $6 resistor if I can!

What $6 resistors?

https://www.digikey.com/en/products/detail/te-connectivity-passive-product/RGP0207CHK1G0/2389890https://eu.mouser.com/ProductDetail...=sGAEpiMZZMtlubZbdhIBIFho3SHfDXSt5nRQ4pdsqnc=
So if these end up getting sold, what's our design fee?

 

[Андрій Чубака]

Small question about connecting 2 sides capsule to preamp. So as i understand for this i need just connect 2 sides of capsule with wire and place some capasitor like 100nf between 2 sides of capsule?

 

[Khron]

Small question about connecting 2 sides capsule to preamp. So as i understand for this i need just connect 2 sides of capsule with wire and place some capasitor like 100nf between 2 sides of capsule?

Not necessarily - unfortunately the actual answer is, as in so many other cases, "it depends" (on a handful of factors, not the least of which is how the capsule is connected to the rest of the circuit).

 

[Андрій Чубака]

For example if using opa alice from Jules pcb circuit with hex dc dc and i want omnidirectional pattern from 2 sides capsule. Possible make it this way with simple wire and capacitor?

 

[Khron]

For example if using opa alice from Jules pcb circuit with hex dc dc and i want omnidirectional pattern from 2 sides capsule. Possible make it this way with simple wire and capacitor?

Well, that still really depends, how you have the capsule connected.

And i don't mean to be mean, but just throwing words around (like "opa alice from Jules pcb") is not the best idea - not all of us, who could and would otherwise like to help, have the time or patience to dig up schematics of a circuit that may or may not be the same one that you're using, and work on assumptions. Just a friendly tip

 

[Андрій Чубака]

I mean circuit like this. Of course i can just try later. But i want at least try ask about it before i have 2 sides capsule in my hands. I have only phone and can't draw it better now.

 

[Khron]

No capacitor needed there. Rear diaphragm disconnected = cardioid; rear diaphragm connected with the front diaphragm = omnidirectional.

 

[Андрій Чубака]

Ok. Thanks.

 

[Admiral-dk]

It's not like I don't get the point of your Trimmer @ the Source Pin (though I would try to avoid using one) ...!
BUT - it is a very bad idea to use one in such a way that you can short it (not a big problem here considered the low current) ...!
Use it with a Serial Resistor - that way you should get a reasonable adjustment + aim for the resistor brings the Trimmer to aprox half a turn, when optimized.

 

[SparkleBear]

Ok, been working on the layout and final schema for this project. I think this is close... I added back in the pad and sorted out some switches, built the footprints and integrated the dc-dc. At first, I just tried to append the boards into each other but it was more trouble than it was worth. I ended up just rebuilding the dc-dc into this mic circuit.







This will be an mxl 990 patriot edition donor body, hence the small footprint PCB... I already powdercoated it. This body is nice because it already has the two switches worked into the design. The screw on bottom of the regular mxl990 does not allow for switches.


Excited for this one...

 

[Khron]

Are you positive C107 & C108 allow enough clearance around that mounting hole/slot?

 

[JW]

Is the one with the tapered headbasket MXL as well? That's a nice looking body.

 

[SparkleBear]

Are you positive C107 & C108 allow enough clearance around that mounting hole/slot?

Good call about checkin that... slight tweak there to make more space. It definitely trips me out to not have the front diaphragm and the rear diaphragm points not floating. But as I understand from the discussion, the only high z lifted point is the backplate-grid junction.



Yay!

Is the one with the tapered headbasket MXL as well? That's a nice looking body.

That is the Mxl990 that’s been powder coated. The nice head basket comes from mic-parts.com. It is a really nice head basket, serious upgrade. They have a black one and a nickel one. Here is a photo of the black one on a standard mxl990 with cream powdercoat on the body.