FET847 Microphone Project Circuit By Jonathan Burtner PCB Layout By Poctop
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Spencerleehorton
Well-known member
Hi,
I have to say, now I've tweaked both these FET847 they sound pretty amazing, I've put in the following:
4.7pf mica
OEP A262A3E transformer
BM800 body
I'll put a link to a very quick test I did with them overhead of the drums, not even really in a precise position, but the stereo image is lovely and wide, the roll off seems to be pretty much perfect.
When used with a FET47 on kick, add a bit of compression to the FET487 and they sound really good.
I used a LA-3A waves plugin, compressing at about 3-5db.
The bass was recorded DI into one of my 1176 same as the acoustic guitar.
This link should work:
https://soundcloud.com/spencer-lee-horton/hiatus
Regards
Spence.
I have to say, now I've tweaked both these FET847 they sound pretty amazing, I've put in the following:
4.7pf mica
OEP A262A3E transformer
BM800 body
I'll put a link to a very quick test I did with them overhead of the drums, not even really in a precise position, but the stereo image is lovely and wide, the roll off seems to be pretty much perfect.
When used with a FET47 on kick, add a bit of compression to the FET487 and they sound really good.
I used a LA-3A waves plugin, compressing at about 3-5db.
The bass was recorded DI into one of my 1176 same as the acoustic guitar.
This link should work:
https://soundcloud.com/spencer-lee-horton/hiatus
Regards
Spence.
0dbfs
Well-known member
Spencerleehorton said:
That's great spence! Which capsule did you use and which source bypass cap?
Cheers!
-jb
Spencerleehorton
Well-known member
Hi,
i used the capsule which came with the BM800 which is an electret and the Cap was a 4.7pf mica.
regards
Spence.
i used the capsule which came with the BM800 which is an electret and the Cap was a 4.7pf mica.
regards
Spence.
Hey,
Just wanted to say, I ended up building a pair of these and I used the 3U audio 9.5:1 87-ish transformer because I had two around not doing anything. The resulting microphone (with asian 47 capsule) sounds really nice--and you can't beat the price. Obviously the 87-type transformer makes the output quite low, but its not low enough to be noisy and I think these will make very nice overheads! I imagine the 3U audio 6.5:1 would also work (and is probably a better choice if you want this to be a vocal mic), but that company's stuff is so cheap you could just get both and see what you like.
I bought the k47 caps used from a friend, so I think my total cost per mic was, like, under 150 dollars.
Just wanted to say, I ended up building a pair of these and I used the 3U audio 9.5:1 87-ish transformer because I had two around not doing anything. The resulting microphone (with asian 47 capsule) sounds really nice--and you can't beat the price. Obviously the 87-type transformer makes the output quite low, but its not low enough to be noisy and I think these will make very nice overheads! I imagine the 3U audio 6.5:1 would also work (and is probably a better choice if you want this to be a vocal mic), but that company's stuff is so cheap you could just get both and see what you like.
I bought the k47 caps used from a friend, so I think my total cost per mic was, like, under 150 dollars.
0dbfs
Well-known member
Yeah - These have turned out to be really great on "everything". Very glad I've made a bunch am interested to hear thoughts from the group now that there are some builds out there on applications where they have worked well and not so great too.
Cheers!
-jonathan
Cheers!
-jonathan
Winetree
Well-known member
I've got 4 of these built with 847 stuffed boards mounted in BM800 bodies.
I received 8 of the group buy capsules (4-47s and 4-C12s).
Which capsules should I use, I'm thinking all 4 - 47s, or 2 of each.
Should I use the cinemags transformers?
Any comments?
I received 8 of the group buy capsules (4-47s and 4-C12s).
Which capsules should I use, I'm thinking all 4 - 47s, or 2 of each.
Should I use the cinemags transformers?
Any comments?
Hey Everybody!
Long time lurker. First time poster. I'm seriously contemplating building this FET847 as my first Poctop board mic.
I have a question about biasing the FET. In the thread starter Poctop said:
So in Andrew Shaap's build (http://www.vintagemicrophonepcbkit.com/Neumann%20U87%20Build.htm), he says:
Connect your mic preamp of choice, preferably one that works, and turn on the phantom power. We’re going to calibrate the drain on the microphone to 11.5 volts. Take your multimeter and put the red probe on r6. This is right next to the FET. Take your black probe and put it on the ground hole. Take a small flat-head screw driver and tweak the pot until you measure 11.5 volts.
I've read using an oscilloscope and injecting a 1K tone into the circuit is the best way to bias the FET, but I don't have an oscilloscope so I was going to do what Schaap did. My questions are:
a) If R6 is the red probe point of contact for the U87, what is the corresponding probe point for the FET847?
b) Would I still be measuring the drain to 11.5v on the FET847?
Thank you in advance for answering my noobie questions. I really did reading this board. There are a lot of smart and interesting people here. I have a serious interest in tinkering with mics and want to learn as much as I can.
Long time lurker. First time poster. I'm seriously contemplating building this FET847 as my first Poctop board mic.
I have a question about biasing the FET. In the thread starter Poctop said:
poctop said:
So in Andrew Shaap's build (http://www.vintagemicrophonepcbkit.com/Neumann%20U87%20Build.htm), he says:
Connect your mic preamp of choice, preferably one that works, and turn on the phantom power. We’re going to calibrate the drain on the microphone to 11.5 volts. Take your multimeter and put the red probe on r6. This is right next to the FET. Take your black probe and put it on the ground hole. Take a small flat-head screw driver and tweak the pot until you measure 11.5 volts.
I've read using an oscilloscope and injecting a 1K tone into the circuit is the best way to bias the FET, but I don't have an oscilloscope so I was going to do what Schaap did. My questions are:
a) If R6 is the red probe point of contact for the U87, what is the corresponding probe point for the FET847?
b) Would I still be measuring the drain to 11.5v on the FET847?
Thank you in advance for answering my noobie questions. I really did reading this board. There are a lot of smart and interesting people here. I have a serious interest in tinkering with mics and want to learn as much as I can.
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