FET847 Microphone Project Circuit By Jonathan Burtner PCB Layout By Poctop

[Rybow]

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

 

[burbela]

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!

 

[Ricardus]

Does anyone know what size the BM800 mic body is tapped for? The two holes that mount the PCB to the body. They're smaller than #4 English, so maybe M2.5?

 

[Khron]

Quite likely - smaller than M3, if memory serves, but definitely not as thin as M2.

 

[karloff70]

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.

 

[Ricardus]

I'm doing a version of this with a different board. I'll be ordering the capsule and transformer next week. I already have the bodies and two PCBs built up. Can't wait to hear it.

 

[rock soderstrom]

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?

 

[Ricardus]

Excited to build two of these with the Arienne fIat k47 capsule.

Oh! I'm not familiar with Arienne. Has anyone used their stuff? How is it?

 

[Khron]

Oh! I'm not familiar with Arienne. Has anyone used their stuff? How is it?

https://groupdiy.com/threads/soliloqueens-k87-k67-and-k47-capsules.81968

 

[Ricardus]

https://groupdiy.com/threads/soliloqueens-k87-k67-and-k47-capsules.81968

OK. I guess I'll take two please of the K47s!

 

[Khron]

OK. I guess I'll take two please of the K47s!

You'll have to contact her (at least through that thread), or rather, place an order through her webshop

 

[Ricardus]

You'll have to contact her (at least through that thread), or rather, place an order through her webshop

Where will they be shipping from?

 

[karloff70]

The load of the FET circuit through the output would be a little higher, that could result in a little more THD, right?

ProbabIy. I don't think it wiII make me hate it though. And the tiny beyer shouId scuIpt the big bottom of that capsuIe down in a nice way me thinks.

 

[Khron]

Where will they be shipping from?

https://groupdiy.com/threads/soliloqueens-k87-k67-and-k47-capsules.81968/post-1071992

 

[Ricardus]

https://groupdiy.com/threads/soliloqueens-k87-k67-and-k47-capsules.81968/post-1071992

Yes. I know the domain.

Where in the real world? US? Europe? Other?

 

[Khron]

I was trying to steer you towards asking about this, on THAT thread, where @soliloqueen is most active, and which is dedicated entirely to that

 

[klem]

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.

 

[Khron]

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.

 

[negaikast]

Yes. I know the domain.

Where in the real world? US? Europe? Other?

My Flat K47 came from Michigan USA.

 

[Ricardus]

My Flat K47 came from Michigan USA.

Thanks.