It looks like the t14 solved the issue. It works like a charm, and sounds huge now. Strange since the leads on the t14 and telefunken eab primaries and secondaries all measure close to the same resistance. Thanks for the help Spencer.
Neumann U47FET Clone: D-U47 FET Microphone Project PCB Build thread
- Thread starter poctop
- Start date
Help Support GroupDIY Audio Forum:
Spencerleehorton
Well-known member
Great stuff, it’s always good to find the problem, happy days.
Spencerleehorton
Well-known member
maarvold said:
https://www.mouser.com/ProductDetail/633-SS22SDP2
https://www.mouser.com/ProductDetail/633-SS12SDH2
I like the side position for the LC switch, since it keeps my fat fingers farther from the components.
Mike
No pics, but I.finished my mic a couple of months ago (Beesneez k7, AMI T49), and love it. Wasn't expecting to be blown away, but the first time I heard playback of a kick drum recorded with it, it was a desk-rattling experience!
shot
Well-known member
I've built this mic around two years ago. Nothing fancy to post a photo since it looks like every other mic in this thread (except Spence's diy bodied units!). It's a GT-2B body by Chunger.
I allways felt that it sounds weird on some sources. Sometimes it would be great, but on some vocalists and instruments it would suck big time! Especially since I built some other mics so I had others to compare with.
Few days ago I wanted to check what is going on with it. I tried swapping FET, going with 1000pf on C1, swapping capsule with spare one I had... I was checking freq. curve in a primitive way - putting headphone on the grille in front of capsule and doing sweep and playing pink noise. What I noticed in every situation is that I had a deep notch around 800-900 Hz. And it was a bit bumpy around 2.4k. There was nothing I could do to fix it. At least nothing in terms of component replacement.
I've put dummy capacitor instead of capsule and injected pink noise into the circuit to see if it has anything to do with bad capsules or mic acoustics - and it was flat this time! So there's actually nothing wrong with components...
After a day of experimenting and countles assemble-dissasemble cycles, I found out that the problem is with GT-2B body! It is resonant inside. When you assemble and screw the mic there's a large gap from grille/capsule into pcb section. If you stuff that gap with sponge foam it will fix this nasty 900Hz notch! It was an easy fix!
Try it!
You may seem that this mic sounds good already. But it's a one minute mod. Nothing to solder or desolder. Just some sponge foam on top of the pcb to fill area from pcb to the inner edge of the body. Try it and you can take it back if you don't like it.
Now I'm on a quest to find something better than this ugly sponge since I feel it will degrade in few years. I need something that will last longer.
just my observations...
Luka
I allways felt that it sounds weird on some sources. Sometimes it would be great, but on some vocalists and instruments it would suck big time! Especially since I built some other mics so I had others to compare with.
Few days ago I wanted to check what is going on with it. I tried swapping FET, going with 1000pf on C1, swapping capsule with spare one I had... I was checking freq. curve in a primitive way - putting headphone on the grille in front of capsule and doing sweep and playing pink noise. What I noticed in every situation is that I had a deep notch around 800-900 Hz. And it was a bit bumpy around 2.4k. There was nothing I could do to fix it. At least nothing in terms of component replacement.
I've put dummy capacitor instead of capsule and injected pink noise into the circuit to see if it has anything to do with bad capsules or mic acoustics - and it was flat this time! So there's actually nothing wrong with components...
After a day of experimenting and countles assemble-dissasemble cycles, I found out that the problem is with GT-2B body! It is resonant inside. When you assemble and screw the mic there's a large gap from grille/capsule into pcb section. If you stuff that gap with sponge foam it will fix this nasty 900Hz notch! It was an easy fix!
Try it!
You may seem that this mic sounds good already. But it's a one minute mod. Nothing to solder or desolder. Just some sponge foam on top of the pcb to fill area from pcb to the inner edge of the body. Try it and you can take it back if you don't like it.
Now I'm on a quest to find something better than this ugly sponge since I feel it will degrade in few years. I need something that will last longer.
just my observations...
Luka
That's funny: I had completely forgotten that--without even listening first--I did A LOT of damping on that mic body with BluTack... enough that it's tricky to remove the barrel unless I'm careful. I typically do this with all my large diaphragm mics, so I had kind of let it go out of the memory banks. ESPECIALLY with a mic I'm going to stick right next to a LOUD kick drum, I don't want any energy storage or rattling from the mic body itself. And yes--I used the GT-2B.
shot said:I've built this mic around two years ago. Nothing fancy to post a photo since it looks like every other mic in this thread (except Spence's diy bodied units!). It's a GT-2B body by Chunger.
I allways felt that it sounds weird on some sources. Sometimes it would be great, but on some vocalists and instruments it would suck big time! Especially since I built some other mics so I had others to compare with.
Few days ago I wanted to check what is going on with it. I tried swapping FET, going with 1000pf on C1, swapping capsule with spare one I had... I was checking freq. curve in a primitive way - putting headphone on the grille in front of capsule and doing sweep and playing pink noise. What I noticed in every situation is that I had a deep notch around 800-900 Hz. And it was a bit bumpy around 2.4k. There was nothing I could do to fix it. At least nothing in terms of component replacement.
I've put dummy capacitor instead of capsule and injected pink noise into the circuit to see if it has anything to do with bad capsules or mic acoustics - and it was flat this time! So there's actually nothing wrong with components...
After a day of experimenting and countles assemble-dissasemble cycles, I found out that the problem is with GT-2B body! It is resonant inside. When you assemble and screw the mic there's a large gap from grille/capsule into pcb section. If you stuff that gap with sponge foam it will fix this nasty 900Hz notch! It was an easy fix!
Try it!
You may seem that this mic sounds good already. But it's a one minute mod. Nothing to solder or desolder. Just some sponge foam on top of the pcb to fill area from pcb to the inner edge of the body. Try it and you can take it back if you don't like it.
Now I'm on a quest to find something better than this ugly sponge since I feel it will degrade in few years. I need something that will last longer.
just my observations...
Luka
In my DIY mic bodies, I always use bonded acetate fibre, which is long lasting and will not deteriorate. The same sort of thing is inside cushions or pillows. One other good thing is that is is a good insulator, so should not affect the circuit as it comes in contact with components or the underside of a circuit board. In a couple of BM800 bodies I used, I found that the grille was resonant, and used the fibre on top of the capsule to dampen that resonance. Worked well.
Kindest regards,
zephyrmic
Kindest regards,
zephyrmic
That would be true. Also in the bodies I made, I isolated the capsule and grille from the part that holds the circuit board/s. Only the leads to the capsule go through. Actually, in using electret 26mm. capsules meant that high impedance circuitry was on a small board directly behind the capsule, so no long high impedance leads to the main circuit board.
Kindest regards,
zephyrmic
Kindest regards,
zephyrmic
Just finally going to finish this build(first mic) as i have a couple projects coming up. Using cinemag 13101, danys D7 and gt2b body.
I did make a plexi plate that to replace the metal one that the capsule cradle screws into. That being said, I had something i wanted to clarify regarding wiring the capsule:
with danys D7, i can use either side as backplate? just pick one side and wire as needed?
and since im using plexi plate under the cap, do i need to ground the cradle? as in use the post coming from cradle and wire to ground?
lemme know if im being dumb. thanks guys
I did make a plexi plate that to replace the metal one that the capsule cradle screws into. That being said, I had something i wanted to clarify regarding wiring the capsule:
with danys D7, i can use either side as backplate? just pick one side and wire as needed?
and since im using plexi plate under the cap, do i need to ground the cradle? as in use the post coming from cradle and wire to ground?
lemme know if im being dumb. thanks guys
egroys
Well-known member
I just purchased all of the bits and am excited to dive in!
What I wanted to know is if anyone can speak about it's SPL handling - I intent to use this mainly on kick drum.
Do I need to have any sort of attenuation pad?
Thank you in advance!
What I wanted to know is if anyone can speak about it's SPL handling - I intent to use this mainly on kick drum.
Do I need to have any sort of attenuation pad?
Thank you in advance!
Similar threads
