MK-U47 - build thread

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ioaudio

Well-known member
Joined
May 11, 2005
Messages
2,087
Location
vienna/austria
MK-U47.jpg

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

MK-U47-Kit.jpg


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:
PICT0125.JPG



-----------------------------------------------------------------------------------------------------------------------------------------------------------------------------
BUILD:

Schematic:

MK-U47_Schematic.GIF


Wiring Plan:
Mk-U47%20Wiring.jpg


we start from the bottom up.

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Use small pieces of wire to bridge contacts as shown

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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

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Unscrew this resistor

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Solder yellow and red wire

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use shrink tube for isolation

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mount the resistor back in

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

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carefully place the ring and tighten

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

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

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Solder together the boards as shown, check for right angle

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place and solder all resistors as shown

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place and solder all wires as shown

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

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

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

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Place and solder the two green capacitors as shown

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

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

Rubber_Band.jpg

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unscrew these parts

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mount the tube sockets, check for orientation!

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bend and add a solder lug

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attach and solder short black wire

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Wire up as shown

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attach the rubber band

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mounting the tube deck

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feed through the wire sleeve

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

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

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bend and place the solder lugs as shown

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a small wire bridge, do not solder yet

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

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do not bend the contact after soldering or i will break



you can hold the tiny contact like this for placement

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to have free access, slide the middle lug away

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the contacts inside the glass envelope must be oriented this way

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solder second side only after orientation is correct

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

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the teflon feed throughs

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

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solder the two black wires

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mount the highZ board + spacer as shown

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attach the wires to the teflon feed throughs

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attach the rest of the wires

hiZ-wiring.jpg


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place the tubes

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Shown with a Flea capsule holder

PICT0125.JPG





 
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 ?
 
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!
 
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.
 
Matador said:
I like the tool marks!  One could make a kick-ass steampunk microphone!

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)

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?
 
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