FET847 Microphone Project Circuit By Jonathan Burtner PCB Layout By Poctop

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Hello!
Who can explain me please how to connect Rear side of capsule?
As I can see front side of capsule and back is marked in circuit, but rear side of capsule wire not marked.
And also this jumper for card/omni switch, right?
View attachment 93243
Hi Burbela. The jumper is for after you set the bias for the FET with the trimmer. You can install a resistor equal to the value you measure on the trimmer, and then use the jumper to bypass the trimmer. In my case, I biased the FET with the trimmer and just left it as is.

This board is setup to hardwire cardioid or omni. You have to figure out a way to mount a switch if you want both. Wire the back diaphragm to the switch, and then the switch to the same pin the front diaphragm is connected to
 
Hi Burbela. The jumper is for after you set the bias for the FET with the trimmer. You can install a resistor equal to the value you measure on the trimmer, and then use the jumper to bypass the trimmer. In my case, I biased the FET with the trimmer and just left it as is.

This board is setup to hardwire cardioid or omni. You have to figure out a way to mount a switch if you want both. Wire the back diaphragm to the switch, and then the switch to the same pin the front diaphragm is connected to
Got it. Thank you very much!
 
Excited to build two of these with the Arienne fIat k47 capsule.

Has anyone here used beyer 5:1 mic transformers in this build? Seems from 6.5:1 to 5:1 shouldn't be too much issue, no? And a bit more output. My gut feeling says it should sound sweet. Let's see.
 
Excited to build two of these with the Arienne fIat k47 capsule.

Has anyone here used beyer 5:1 mic transformers in this build? Seems from 6.5:1 to 5:1 shouldn't be too much issue, no? And a bit more output. My gut feeling says it should sound sweet. Let's see.
Interesting question, I also have some Beyer and Haufe 1:5 lying around, would be nice if we could use them successfully here.

The load of the FET circuit through the output would be a little higher, that could result in a little more THD, right?
 
For solid-state mics like this, KM84, etc. with 1GR x2, how important is the matching? There's a significant cost difference when building pairs of these from 5% to 1%.

More generally, if looking to use mics as a matched pair, do tolerance deviations for pairs of R have more of an impact (be it level or FR) in the high-impedance section (R1,2) or as V increases towards output (R7,8 or R9,10)? The schematic note for R9,10 "match 0.4%" makes me think that, the higher the V, the more important the matching, which seems ostensibly counter-intuitive in my muddled, rudimentary understanding.
 
The 1G resistors need no particularly close tolerance; the rest of the resistors can be 1%; the two 2.2k resistors between XLR pins 2 & 3 you'll want to match as closely as feasible though (they cost next to nothing, so just buy a couple tens and match a few pairs manually).

It's not about the voltage in the particular area of the circuit, but the role they play in the circuit. Those two 2.2k's you'll want as closely matched as you can get them, in order to maximize the common-mode rejection ratio (in other words, immunity to outside interference permeating into the cable).

Capacitors you'll be hard pressed to get in tolerances under 5%, but you'll likely be at the mercy of the mechanical / manufacturing tolerances of the capsules, rather than the electronics, at the end of the day.
 
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