FET847 Microphone Project Circuit By Jonathan Burtner PCB Layout By Poctop

[0dbfs]

You could graph the frequency response of the circuit to quantify what you are hearing.

Replace capsule with cap. Inject signal. Measure output. Sweep frequency and notate changes in output level. Make a spreadsheet of level and frequency. Graph it.

Compare the two mic's with that test to see how far apart they are.

Swap in a new fet to see if it changes.

Could be another component.

Cheers
-jb

 

[ivansc]

Waiting for my pcbs to arrive and really looking forward to getting my feet wet.

Hopefully going to sort out the transformer with Spence in the near future, which will cut down on any more transatlantic waiting time!

 

[G-Sun]

Just to share my experience. I had no problem fitting, both ck12 and k47 style capsule either in bm700 and bm800 mics. Enough room for capsule and mount.

Thank you for sharing!
Where did you buy your capsules?

 

[ivansc]

I am about to buy mine from Microphone parts UK - I believe they are actually based in France for europe, unless things have changed in the last few years.

Unless I have the wrong firm I did some translation work for them  for their english language website text a while back.

 

[Rasta3]

You could graph the frequency response of the circuit to quantify what you are hearing.

Replace capsule with cap. Inject signal. Measure output. Sweep frequency and notate changes in output level. Make a spreadsheet of level and frequency. Graph it.

Compare the two mic's with that test to see how far apart they are.

Swap in a new fet to see if it changes.

Could be another component.

Cheers
-jb

Thanks for the tips, I'll try to figure it out.

Thank you for sharing!
Where did you buy your capsules?

I bought them from capsule groupbuy, here from this forum.

 

[G-Sun]

I bought them from capsule groupbuy, here from this forum.

Ok thanks! Maybe I should try to get hold of one of those then.
I checked with microphone-parts and the mount there was to big for this body.

 

[Carnesd]

Does any body have the Schematic and BOM files they could send me,  went to build this mic yesterday and looks like Dany's dropbox is down and not sure when it will come back up.  I'd like to get building tonight if possible.  Thanks in advance

 

[0dbfs]

Here is a ZIP with the original documentation - BOM, Schematics, and some PDF's on the Cinemag transformer for BV7 replacement. Project notes.

I'm sure Dany's links will back up soon.

Cheers and good luck with the mic(s)!
-jb

*** HINT ***
Change file attachment extension from .PNG to .ZIP when you download.

 

[Carnesd]

Here is a ZIP with the original documentation - BOM, Schematics, and some PDF's on the Cinemag transformer for BV7 replacement. Project notes.

I'm sure Dany's links will back up soon.

Cheers and good luck with the mic(s)!
-jb

*** HINT ***
Change file attachment extension from .PNG to .ZIP when you download.

Sweet exactly what I needed,  guess I need to learn to download any project info before hand.  Cant wait to see how this thing sounds, Thanks again!

 

[ivansc]

Ok thanks! Maybe I should try to get hold of one of those then.
I checked with microphone-parts and the mount there was to big for this body.

What did you wind up doing for a capsule? I found the 3-d print project for a mount on here but am still dithering over what capsule/mount to buy. Definitely going with something like an RK47 but, as is the way of these things, there seem to be a lot of choices...
Good news is my Mouser order arrived early and is complete so the soldering iron will be out later.

 

[ivansc]

Wow such a quick build! Just wish I had bought a decent pair of side cutters - min are dead. And my fine soldering skills....!!!!

Transformer I ordered turned out to be too big  & still scratching my head over the capsule....

One thing: middle leg of the FET seems to be going overland on most of your builds.  Not a problem for me, but  if I DO decide to connect on the underside, are there any issues with interference or other pickup involved I should know about?

 

[Delta Sigma]

Wow such a quick build! Just wish I had bought a decent pair of side cutters - min are dead.....

I love these cutters for trimming component leads: http://ca.mouser.com/ProductDetail/Apex-Tool-Group/MS545JV/?qs=sGAEpiMZZMuxaxGVT3gSIqaVf4WVTCQhaxnQ7q4aclc%3d

I use very nice Snap-on flush cuts at work but for PCBs and other component trimming at home I prefer the smaller semi-flush Xcelites. I also have the tapered ones but use them less, mostly on PCBs.

 

[G-Sun]

Starting my build now.

A few questions:
- c2;c3;c6;c4 is marked polarized. But the tantalum caps are non-polarized, right?
- C2: Less bass, is 4,7uf for flat response?
- "The Silk Screen contains 1 Errata the P+ , P- and S+ , S- are Inverted but the Picture shown in this thread shows the proper position":
My pcb seems exactly like the picture. Does that mean this is fixed on my revision?
- Hi-z-nodes for back and front capsule are insulated. I'm using cardioid only.
How are these connecting to the rest of the pcb?

 

[useme2305]

Starting my build now.

A few questions:
- c1;c2;c3 is marked polarized. But the tantalum caps are non-polarized, right?

tantalums are polarized

 

[G-Sun]

tantalums are polarized

Oups... thanks! Hope I was lucky. Why equal legs then?
Need to get my magnifier ready for that microscopic print.

Edit: 3/4 right, that's luck. Me and desoldering are not good friends.
But, managed to get the last one in right as well 

 

[G-Sun]

There must be something I don't understand about R1; R2 and C1 and their connection to FO-turret.
I see different pictures connecting in different ways.
And is Q1 to be manually connected as well?

I see I jumped in soldering, before understanding this too well..

 

[G-Sun]

The capsule doesnt have a ground connection. The backplate is connected via the 1g extremely hi z to the filtered and stable 48v supply which provides a DC voltage reference. The front diaphragm connection feeds signal into the fet gate for cardioid and if you want omni just connect the rear diaphragm also into the fet. Those capsule connections are all very hi impedance so any dirt oil or foreign material bridging to ground or other circuit nodes will lead to undesireable noises. Keep it tidy and clean.

Ok, I connect back capsule to turret Bck? And then, nothing further?
And front to FO turret, the FO turret to C1, R1 and Q1G?

 

[G-Sun]

Ok, so I just follow poctops schematic:
FO to C1; R1 and Q1G
Bck to C11 and R2
this is for cardioid.
Using some wire or leftovers

Then if I would like omni:
Bck to Q1G ??

Capsule ground to Glink?
(My capsule came with aground wire)

 

[G-Sun]

Is this right?

 

[Vac11]

Sorry, but this is not right... You have to make a floating conection from the other side of PCB.