martthie_08

Re: MK-U47 - build thread
« Reply #680 on: March 12, 2019, 06:07:32 AM »
I've taken liberty to resurrect the build information.
If this should disrupt anyones copyright please let me know and I will delete this post.


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:



-----------------------------------------------------------------------------------------------------------------------------------------------------------------------------
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








vinylwall

Re: MK-U47 - build thread
« Reply #681 on: July 16, 2019, 09:55:50 AM »
In case anyone is interested, I have a fully assembled iOAudio MK-U47 for sale:
https://www.ebay.com/itm/183894640663
« Last Edit: July 22, 2019, 09:25:34 AM by vinylwall »
Jimi Ray

Re: MK-U47 - build thread
« Reply #682 on: February 25, 2020, 01:27:57 AM »
Hi all,

Took me 5 years but am finally wiring up the cable for my mic. I finished the mic (except for wiring the capsule) about 4 years ago. I finished the PSU about 3 years ago. Cable was done today. Capsule now to go in.

So, now I want to wire in my Thiersch blue line capsule. I have a (hopefully not stupid) question I couldn't find an answer to in the thread... which side of the capsule is which? How to tell the front of the capsule? Does it matter or not?



Thanks,
Chris
"Kind of like going into Safeway at 4 in the morning and chugging a beer in the produce section; been there, done that." - CJ

"We're not making an atomic bomb, just cooking a few electrons." - PRR

djn111

Re: MK-U47 - build thread
« Reply #683 on: February 25, 2020, 05:03:29 AM »
Hello,

Congrats :-) I hope it will sound great !

But to answer your question, they are identical on both side's, and closely matched if all is right.

Let is know how it turned out ?

DJN

Re: MK-U47 - build thread
« Reply #684 on: February 25, 2020, 11:58:49 AM »
Thanks for the info.

My gosh! This mic!  ;D

I just did a quick connect of the capsule so no real time to run it through its paces today. I'm using JAN NOS 6028s. Lots of people saying too clean/no bottom with those tubes. That may be the case but it sounds pretty glorious as is! I didn't really burn in the tubes, BTW. I also don't notice any noises from the tubes. Did I get lucky?

One thing I did notice is that I had to increase the gain on the mic pre (CAPI V28) quite a bit during the quick test in order to get a decent signal. Is that normal or do I have a failure in constructing/wiring?

TBH, I was finishing up the mic because I was planning on selling it to raise funds for a potential soon-to-be move. However, after hearing it briefly, I may have to reconsider!

To sum up, wow!

Chris
"Kind of like going into Safeway at 4 in the morning and chugging a beer in the produce section; been there, done that." - CJ

"We're not making an atomic bomb, just cooking a few electrons." - PRR

Pip

Re: MK-U47 - build thread
« Reply #685 on: February 26, 2020, 02:32:24 PM »
How hot did you have to make the pre for what was a usable level? Check your voltages again would be my first suggestion.

The JAN 6028/408a  tubes are the lowest noise in my tests but are also, to my ears the least musical, but, IMO,  there is nothing low noise about these tubes compared to other options for this type of copy.

http://groupdiy.com/index.php?topic=47112.msg764053#msg764053
http://groupdiy.com/index.php?topic=47112.msg764111#msg764111

more at my website in the blog section.

M7 capsules are interesting  as they share the same backplate and are glued, IMO again, they are all slightly different side to side. I always listen intently to them and if there is one side that seems to my ears more what I want to hear (so totally subjective to say the least) I make that the front. I see you went for the blue line old style.
Pip
New York City
http://geosonixlab.com

Re: MK-U47 - build thread
« Reply #686 on: March 11, 2020, 10:06:05 AM »
Guys, my Mk-u47 sounds great, but I have a big issue, which is intermittent static. I've burnt in the tubes for many hours but the problem remains.  I've left it recording for a few hours to observe and about every 10 minutes (on average  but not regularly) there is a burst of static, like strong wind or vibrating white noise. It's the type of sound I would normally associate with tube burn-in or tube failure but weird that it disappears for long periods then returns. Any clues? Is the best first move simply to replace the tubes? thanks in advance for any advice.

Pip

Re: MK-U47 - build thread
« Reply #687 on: March 11, 2020, 03:29:24 PM »
Yes! Tubes are often the culprit which ones have you chosen?

Also double check that the filter caps in PSU are healthy.

Lastly what capsule are you using? Does the problem exist in Omni and Cardioid modes?
Pip
New York City
http://geosonixlab.com


 

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