MK-U47 - build thread

MK-U47 Tube Microphone Kit featuring:

Costum Headbasket made by Flea with Pattern Switch
Brass made body tube and bottom bell, bead-blasted and nickel-plated
Stainless internal structure
Bv.08 Transformer with 8 seperate sections from my own production
6028 single supply circuit with all parts including



including (back left to right):

body tube
bottom bell with power resistor mounted + internal structure
Headbasket pattern switch
Transformer + resistor board
High-Z board with screws, teflon isolators, shims for variable capsule mount height
solder lugs and subminiature reed-contact
Black rubber band for tube shock-mount
Tube deck + tube sockets, screws,


(front left to right):
Wiring, yellow wire sleeve, shrink tube
Binder connector for mic and cable
Bv.08 Transformer
PIO and styroflex capacitors, resistors

to complete the microphone, you'll need:
a capsule + holder
a single supply 105v PSU
a microphone cable (cable connector to mic included)

Completed kit with Flea capsule holder:



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BUILD:

Schematic:



Wiring Plan:


we start from the bottom up.



Use small pieces of wire to bridge contacts as shown





wire the connector according to the original schematics
Solder a lug to the end of one black wire
1: White
2: Blue
3+4+6: Black x 2
5: Red



Unscrew this resistor



Solder yellow and red wire



use shrink tube for isolation




mount the resistor back in



unscrew the ring of the connector and place it
in the bottom bell, aligning the keyway/slot



carefully place the ring and tighten



unscrew the nut and place the solder luck and re-tighten





paint the transformer/resistor board (not shown: use a file after breaking)




Solder together the boards as shown, check for right angle





place and solder all resistors as shown




place and solder all wires as shown








Be careful handling the transformer
place and solder the transformer as shown





Before soldering the big capacitors it's time to mount the whole thing into the mic







insert the screws and attach the nuts, do not overtighten!





Place and solder the two green capacitors as shown








The yellow sleeve will be cut like this to fir through the hole





Carefully cut and drill (pierce) the rubber band as according to this measurements




unscrew these parts



mount the tube sockets, check for orientation!





bend and add a solder lug





attach and solder short black wire



Wire up as shown













attach the rubber band




mounting the tube deck




feed through the wire sleeve



attach the yellow, red and blue wire to the corresponding pins




Be careful with overheating when building the highZ portion of the circuit



bend and place the solder lugs as shown







a small wire bridge, do not solder yet



the reed contact must be oriented and placed carefully BE VERY CAREFUL HERE





do not bend the contact after soldering or i will break



you can hold the tiny contact like this for placement



to have free access, slide the middle lug away




the contacts inside the glass envelope must be oriented this way





solder second side only after orientation is correct



more wire bridges and placing parts, place everything before soldering, solder quickly









the teflon feed throughs



push the carefully to place, grabbing them by the top teflon part







solder the two black wires



mount the highZ board + spacer as shown








attach the wires to the teflon feed throughs



attach the rest of the wires





place the tubes



Shown with a Flea capsule holder

Wow. Yes. 

Excellent work, Max!
regards
Bernd

Great work ! This is definitely the year of the mic !

Interrested in 1 (without labeling on it) depending on price... Do you have a price ballpark ?

8)

Amazing work mate-just starting the same process with C12. Ive got a matched pair of Tim's capsules and just can't put them in a Chinese body of the wrong dimensions and materials! Certainly like to purchase 1 of these when available!

;D

Are you using cutting fluid?  I see tool marks in the bases.

IMO it is good to get the best finish you can when turning metal on a lathe or milling it before finishing it.
Correct speed, tool shape,cutting rate and cutting fluid brushed on or mist or flood.  I like mist setups mix of air to remove chips and cutting fluid when you want to see what is happening.

thanks for your kind comments.
The labeling on the mic is only temporary for my cad drawing.
I'll try to keep the price as DIY-friendly as possibly, but keep in mind that the used copper-alloys do cost like 4 to 6 times more than materials used in other mic housings.

Gus, shown is a pic from after the roughening job done - those are not finished yet.

I like the tool marks!  One could make a kick-*** steampunk microphone!

Guesstimate on price ?

Not just yet, Greg - still need to evaluate pricing on the finish (galvanisation)

Matador said:

I like the tool marks!  One could make a kick-*** steampunk microphone!

Click to expand...

i also like em, working with brass is just nice.
I got two pm's asking why i would make my housings from brass - the vintage U47 in the lower serials was made from brass (incl the body tube)  like this:
http://www.jogis-roehrenbude.de/Roehren-Geschichtliches/Neumann-Mikro/U47/U47.htm

Brass seems very sensible to me - much easier to work with on a small run. Although your production run looks quite big!

Anyway, looks good so far - I'm watching with interest.

I got two pm's asking why i would make my housings from brass - the vintage U47 in the lower serials was made from brass (incl the body tube)

Click to expand...

Yup.
Many seem to think aluminum is the true original material.
Most numbers, yes.
First, no.

About the brass. Strictly speaking, that would be copper/zinc. But "gunmetal" also contains tin (copper/tin=bronze, although in a looser sense just about any copper alloy is called bronze) and sometimes even lead. It's called red brass here:
http://en.wikipedia.org/wiki/Gunmetal
Max, could you tell us the metals and percentages in your alloy?

i use both - brass (MS58 and MS63) and gunmetal (Rg7)

OK, thanks. 

Working on the lower rings for the headbasket - this material is RG7 - it's a bit darker than brass

Looking great! Definitely interested in one when these become available.

Nice!  ;D