FINISHED: JKSN-U67

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JessJackson

Well-known member
Joined
Dec 17, 2009
Messages
439
Location
Los Angeles
I set out to build a u67 inside a u87ai body,

I have the untouched genuine modern k67 which came with the u87ai, I have a very low noise NOS telefunken ef86 and Olivers bv12,

I am utilizing the yellow Vishay 1813 0.01uf caps throughout the circuit as I couldn’t source the Wima Tripofols and the metal oxide in the high impedance section under the head basket.

As for resistors I used all carbon film 1/2 watts with the exception of the 60meg and 400megs which were metal oxide dales

Its all 100% point to point, SUPER quiet mic!! and SO MUCH gain.

The 40hz jumper is running shorter distance across the top circular perfboard section and there was no need to run the traces down into the bottom board for coupling cap as I mounted it next to the tube for easy access  to swap out.

Based on Klaus and a few other guys I decided not to include the bottom board which holds the passthrough filter caps. The 2000pf filter caps don't serve much purpose in this design. "These caps were put in so the mics could comply with German public broadcast specs. Neumann complied with all requirements, but the broadcasters still rejected the model, because it used the "wrong" tube."

Im using Dany's PSU. perfect voltages across entire mic. Bias / plate / grid, output etc...

Things left to do.

Find a couple screws and bolts small enough to travel through transformer and drill holes.
Source Truchel mount.
Powder coat glossy like original u67
design print labels for transformer and outer casing bell.
Source 0.01 wima tfm's and some wire wound high impedance resistors as per original.

This is the best mic I've built.

u671.jpg


u672.jpg


u673.jpg


u674.jpg


u675.jpg


u676.jpg
 
Jim50hertz said:
Very cool Jess. That's quite the build.  8)

+1 Hats Off ,  Initially i Wanted to design the D67 exactely like this but having a U87Ai body was out of question ,
i am curious about this new transformer the BV12 classic Series :)  from Oliver if its sounds even better than the T67 ,  Caution Tough if you plan on drilling the core of the transformer as it will probably impact the final sonics , cannot advice you on this but probably Oliver could ,

Bravo ,
Best,
Dan,
 
AWESOME!

This is what I call DIY.
Quite inspiring.

Will take me a long time to get to this level of craftmanship..
 
I'll add that for those who want the true U67 circuit but in a cost-effective and easier way, poctop's is still the way to go IMO.

But this point-to-point version is something special indeed. I love it.
And some people, like studio owners, may want to have a U67 that looks just like the original (black badge, anyone?), if only to satisfy the customers.  ;)
Pricier solution, though.



Henk
 
poctop said:
Jim50hertz said:
Very cool Jess. That's quite the build.  8)

+1 Hats Off ,  Initially i Wanted to design the D67 exactely like this but having a U87Ai body was out of question ,
i am curious about this new transformer the BV12 classic Series :)  from Oliver if its sounds even better than the T67 ,  Caution Tough if you plan on drilling the core of the transformer as it will probably impact the final sonics , cannot advice you on this but probably Oliver could ,

Bravo ,
Best,
Dan,

Cheers Dany,

I'm not sure if its just the bv12 that sounds different as my the components and circuit is slightly different from yours. (no filter caps, tripple mesh head basket, original capsule, 1/2 watt resistors etc...)

The transformer holes are pre drilled as per the original bv12, I just need to drill the pcb boards to match :)

Jess
 
mickdundee63 said:
Why the u87 and not tlm67 when the latter is cheaper? Is the body different dimensions?

good question, tlm67 was my original plan and then i realized I already had a u87ai that barely gets used.
 
I use ERO caps a lot, since theres a local store that carries most of the values.
However i never really came to a concusion that i love them or not.

Whats your opinion?
Nice build btw.
 
3nity said:
I use ERO caps a lot, since theres a local store that carries most of the values.
However i never really came to a concusion that i love them or not.

Whats your opinion?
Nice build btw.
some caps matter less than others.
 
Hey Jess, I'm hoping you can confirm the following transformer wiring for me for the AMI BV12. I have the data sheet however there is an inconsistency (the data sheet lists one white and two grey wires whereas I have one grey and two whites). I would contact AMI however the very sad news from their organisation is that Oliver Archut has passed away so I'm not bothering them and using the information I already have.

For this reason I have set out the wiring according to the physical transformer below. i'm hoping yours was laid out exactly the same so you can confirm this is correct:


                (to C3) white ---[]---blue (join to green)
            (to c12) yellow---[]---red (to ground)
            (to R18)  grey---[]---white (to c13)
      (join to blue)  green---[]---orange (to C9)

                        both blacks to ground

Any help you are able to provide is most appreciated.
 
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