At4022

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timtimtim

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So I've bought an AT4022 microphone, but I havn't got a lead yet.
Some questions: the 3-pin XLRM connector is labelled signal pins 2 and 3, ground pin 1, so I presume 48v supply is to the metal case? Am I right?
And is that +48v or -48v?
I assume it has a voltage regulator to drop 48v to something lower like 12v? I would like to bypass this regulator if possible so I can run the mic at low voltage, so saving batteries. I can probably work out how to do this myself, but if anyone has any tips on how to do this, and what potentialy catastrophic actions to avoid, I'd be grateful.
 
It should be a standard XLR connection. 2 is HOT, 3 is NOT. The mic draws power. As long as you supply it with the minimum amount of power that it needs you should be good to go. The AT4022 is a 48V mic, so less (or more) than that at your own risk. There are some that draw so little power than they could be run on 12V without much noticeable loss in quality. The AT4022 doesn't appear to be such a mic. As opposed to an SM81 (11 to 52V, 1.2 mA).

AT4022
PHANTOM POWER REQUIREMENTS 48V DC, 3.0 mA typical

According to specs anyway.

http://www.audio-technica.com/cms/wired_mics/4b375fc7ecdd65da/index.html/
 
Phantom is +48V across 6k8 resistors to pins 2 and 3. The AT4022 should be capable of running on lower voltages as it is electret, but it is not specified for voltages lower than 48V. That is rather curious, but you'd need to trace the circuit to see why. It's possible that it does work and that AT for some odd reason chose not to put that in their specification.

If you need to run on lower phantom voltage, it's probably easier to seek out mics that are specified at 12V, which include the discontinued AT3032.
 
I tried to get a 3032 but I couldn't find one in this country (England).
I don't see how I am going to easily get +48v to pins 2,3 if they are connected to the + and - inputs of an op-amp? I suppose I could have the op-amp floating up at 48v above ground? How do they do it?
Do you think there is any point in me trying to bypass the voltage regulator if I can put say 13v into it and still get 12v to the mic's FET cct?
 
I think you should start by studying some schematics. 48V is isolated from the opamp by either a transformer or capacitors. See this thread on the DIY board:

https://homerecording.com/bbs/showthread.php?p=3494813

Here is a typical electret mic schematic--this is basic, AT's could be more involved:

http://www.scotthelmke.com/alice-schematic.jpg

That would work fine, not quite down to 12V, but much lower than 48V. The PNP output is typical of mics, but far from universal. Given that AT used to make 11-52V circuits, but now they say 48V only, the question is why? I don't know, you'll have to trace the circuit. Knowing AT, it will be nearly all SMT parts, and there could be quite a few of them.
 
OF course capacitors why didn't I think of that? I didn't want to use a transformer, though this mic appears to have a transformer in it, or would that be a choke?
Thanks for those links. I'm going to have to do some circuit tracing and testing now. I'm very wary coz I have a tendancy to rush in and make quick decisions and make irrevocable errors, so slow slow slow. Incidentaly when I took the mic apart the capsule unplugged itself and stayed in the tube. Is that normal?
 
Just an update on the AT4022. I've tested it and it sounds beautiful, and it works right down to 12v though the gain possibly drops off slightly at the lowest voltage? The hiss (self noise) sounds about 6dB? lower than my old mic. I can't trace the circuit because there are two electrolytic capacitors cemented onto the circuit board covering up a lot of components and tracks.
Anyway I'm happy :)
 
I've have a pair of 4021's that I really like on acoustic guitar. I've often wondered how the omni version performs.
 
I've never owned a cardoid mic so I dont know how it would compare. I dont like the idea of loss of bass at a distance, and bass boost close up, which you get with cardoid mics.
 
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