Neumann U47FET Clone: D-U47 FET Microphone Project PCB Build thread

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Colorblind

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Just finished mine, and it's working right out of the gate thanks to the help I received here. Lots of headaches along the way with this one though. If you're looking for a "fun" build, you might look elsewhere, like Dany's U87, IMO.
 

Colorblind

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Finally got a chance to put this thing to use. I've got it about 3" in front of the kick, and while nothing sounds "off" about it, the waveform is asymmetrical, which makes me wonder if I've messed something up. Is this normal behavior? Picture attached.
 

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Frank00

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Hi guys, probably a dumb question, but is this Mouser part a suitable alternative to the BC547B transistors in the BOM (those are out of stock)?

https://www.mouser.it/ProductDetail/ON-Semiconductor-Fairchild/BC547BBU?qs=5AtiFsybhAy95gcR20xJtg%3D%3D

Thanks,

Francesco
 

earlfsmith

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Frank00 said:
Hi guys, probably a dumb question, but is this Mouser part a suitable alternative to the BC547B transistors in the BOM (those are out of stock)?

https://www.mouser.it/ProductDetail/ON-Semiconductor-Fairchild/BC547BBU?qs=5AtiFsybhAy95gcR20xJtg%3D%3D

Thanks,

Francesco

Order from Mouser in USA. THey have plenty.
I'l be starting this build soon
 

earlfsmith

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could this be a good replacement for bc557c btf

https://www.jameco.com/shop/ProductDisplay?catalogId=10001&langId=-1&storeId=10001&productId=2169521
 

Frank00

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earlfsmith said:
Order from Mouser in USA. THey have plenty.
I'l be starting this build soon

That is not really an option, as I'm in Italy and import duties would be pretty substantial.
 

earlfsmith

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Frank00 said:
That is not really an option, as I'm in Italy and import duties would be pretty substantial.

would that be the case if im mailing them to you from california?
 

bxershrts

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Question about the "no trimmer" mentioned earlier in the beginning of the thread. Yet i see that there is a trimmer in the build photos and is placed opposite to what the pcb shows for the adjustment screw.

So i ask is the trimmer still needed for biasing capsule polarization voltage?

Thanks again for all your help.
 

duantro

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I understand it can be omitted. Jumper the right pins (as in first post photos ), and use the correct resistor 6.8k on r6
 

bxershrts

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Thanks for your reply Duantro.

I have a few more questions about wiring the cinemag 13101 to the pcb and the correct locations.

On the pcb can the terms be defined to me.. what is :

bck = backplate?
LC  = Large Capsule?
s1b = ?
s1a = ?
Pad = is this an internal switch that can be added?
on = shelf? also is this an internal switch that is added?
FD = front Diaphram is connected to C3? or where is the diaphram connected?

Thanks again
 

duantro

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bxershrts said:
Thanks for your reply Duantro.

I have a few more questions about wiring the cinemag 13101 to the pcb and the correct locations.

On the pcb can the terms be defined to me.. what is :

bck = backplate?    Yes
LC  = Large Capsule?  Low Cut
s1b = ?    These are for headers and jumpers instead of a switch
s1a = ?    These are for headers and jumpers instead of a switch
Pad = is this an internal switch that can be added? Yes or jumpers
on = shelf? also is this an internal switch that is added? Direction for switches or jumpers for pad to be enabled
FD = front Diaphram is connected to C3? or where is the diaphram connected? Look at the photos. At the junction of R1 and the floating cap

Thanks again
If you look real hard at Dany's pcb pdf, the switches kinda make sense. His mic schematics are really tough to read and somewhat cryptic. I.e.: no capsule info, or AA goes to A on schematic, but It isn't labeled there, you have to sort through the build photos. Thankfully the build photos are helpful!
 

bxershrts

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Ahh - you are a good man Duantro!

Yes it is making more sense between the schematic and build photos.

So just so I have this straight in my head - the circuit is already setup for pad and lowcut - then simply adding a header to the pins at s1b and s1a at the top 2 pins engages the pad and LC in circuit?

With the header on the inside 2 pins its out of circuit and at the top 2 pins its in circuit?

so then what is s1a ? Pad
and then s1b is LC?

Then I ask what is the "pad on" for? ...or I guess its a switch or 2 switches at "pad on"....... or i simply use the pins and headers?
I hope I have that correct :)

And lastly I am using the cinemag 13101 - can you instruct me on how to wire in this xfrmer

RT - ROT = Red(1)
BR - Braun = Brown(2)
VI - Violett - Purple = Orange (3)
BL - Blau  Blue  = Yellow (4)
Black is Ground...


Thanks for your wisdom help and guidance.
 

duantro

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bxershrts said:
Ahh - you are a good man Duantro!

Yes it is making more sense between the schematic and build photos.

So just so I have this straight in my head - the circuit is already setup for pad and lowcut - then simply adding a header to the pins at s1b and s1a at the top 2 pins engages the pad and LC in circuit?

With the header on the inside 2 pins its out of circuit and at the top 2 pins its in circuit?

so then what is s1a ? Pad
and then s1b is LC?

Then I ask what is the "pad on" for? ...or I guess its a switch or 2 switches at "pad on"....... or i simply use the pins and headers?
I hope I have that correct :)

And lastly I am using the cinemag 13101 - can you instruct me on how to wire in this xfrmer

RT - ROT = Red(1)
BR - Braun = Brown(2)
VI - Violett - Purple = Orange (3)
BL - Blau  Blue  = Yellow (4)
Black is Ground...


Thanks for your wisdom help and guidance.
The swA and swB are the same as the switch next to it. Look at schematic pdf. Think of headers as the double pole switch. So 2 headers. The low cut is the headers labeled LC.
I think you are correct on cinemag wiring. Mine is wired  1-brown, 2, red, 3-yellow, 4-orange. Search through the thread it’s all in here.
 
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