MK-U47 - build thread

[Winetree]

Wondering, What are the values of the two green P.I.O. caps?

 

[stelin]

1uF 250V and 0,5uF 160V. See the schematic.

 

[audiomsg]

Hi Max
I just wanted to say that I received the parcel with the capsule in it on Saturday, and immediately installed it in the MKU-47 body that I'd already finished.
Apart from a silly wiring mistake I made in the cable, it went without a hitch, and it sounds absoloutely beautiful.
I think I prefer the sound of the Thiersch Blue Line to the Cathedral Pipes M7 in my MK-47, but they are both great mics. (I would say that the CP "Dale" M7 is a touch darker)
You are probably well aware that the body construction of your MK-U47 kit is vastly superior to that of the Equinox Systems body, it's a beautiful piece of engineering, so thank you for making it available to people like me!
Kind regards
Olly Harmer

 

[Category 5]

Max. Are more runs of this project planned? Would love to have a second but would rather fund it later than now. 

 

[ioaudio]

Yes, I'm already working on the next batch.

 

[Energizer]

Hi,
I finished the first MK-U47 (Thiersch red line / Zayance PCB based PSU) and the soldering iron is heating up for the second kit
I LOVE the sound, if you're interested to hear it I just made a video : http://www.youtube.com/watch?v=4FS7DAtWEx4
The tracks are not dry but I hope it can give you an overview when it's used in a mix!
Peace,
Brice Sommen

 

[fazeka]

I was progressing very well with my build, but unfortunately I clumsily broke the reed switch...

Hi Olly,

Unfortunately, me too!   

Did you have to take everything apart again to put in the new reed switch? I'm hoping not...

Thanks,
Chris

 

[ioaudio]

Hi Chris,

this one works http://uk.farnell.com/coto-technology/ri-70gp0715/reed-switch-spst-7mm/dp/1081702

-Max

 

[fazeka]

Hi Max,

Thanks, got it ordered from Newark in the U.S.

Now, just need to build the PSU...

Cheers,
Chris

Hi Chris,

this one works http://uk.farnell.com/coto-technology/ri-70gp0715/reed-switch-spst-7mm/dp/1081702

-Max

 

[stelin]

This i my version of the PSU for the MK-U47. It worked the first time (except I had mounted the LED on the board the wrong way). I got 108V with the trim pot centered! Thats close. Now my MK-U47 is complete, and the testing has stared. I think I will have to put some labels on the PSU (for future generations). This mic will be around many years after I am not  . If anyone wants to see more pictures, I can post them.

 

[stelin]

This is the other side of my PSU. As you can see I have a switch for the dummy load and a trimmer for the B+. Just needs some labels. 

 

[fazeka]

Hi,

Nice! Do you have top, front and back views?

Thanks,
Chris

 

[stelin]

Hi Chris,
This is the front. The PCB is mounted 60mm above the floor. I pushed everything over to one side to make room for the trimmer and the dummy load switch.
The trafo have two outputs: 200V and 6V. I used the 6V for an indicator lamp on the front.
Sorry, did not take any picture from directly above.

 

[stelin]

And finally, this is a view of the back of the PSU.

 

[mgronroos]

Cool, I like the "dual level" setup, Stelin, I might let my self be inspired by that idea..  8)

Solid work!

//Michael

 

[fazeka]

Stelin,

Thanks! Nice pics/build.

I have a stupid question: where's the PSU PCB from?

Thanks,
Chris

 

[wolan42]

From Tony (zayance)
http://groupdiy.com/index.php?topic=53011.0


Beautiful Boards. ;-)

 

[stelin]

I’m now in the process of testing and burning in tubes for my MK-U47. One problem is that there are two tubes in the mic. How do you select the tube with the lowest noise when you have to test them two at a time?
It would be nice to be able to run the mic with only one tube when measuring the noise. But, then the heater will not work, since the heaters are connected in series.
Does anyone have any thoughts or suggestions on that?

I have built two C-12 copies (MataChunger) to. The MK-U47 is about 5dB hotter than the C-12s, but even compensating for that, the MK-U47 is a lot noisier (at least 6db) so far. But then again, I was really surprised how quiet the C-12s with Mullard 12AT7 are.

Does anyone have any experience with the 6028/408a tubes? Do they vary much in noise levels? Do they need a long burn in time?

Thanks!
Stefan

 

[fazeka]

Do they need a long burn in time?

48 hours according to Max.

 

[chunger]

I’m now in the process of testing and burning in tubes for my MK-U47. One problem is that there are two tubes in the mic. How do you select the tube with the lowest noise when you have to test them two at a time?
It would be nice to be able to run the mic with only one tube when measuring the noise. But, then the heater will not work, since the heaters are connected in series.
Does anyone have any thoughts or suggestions on that?

I have built two C-12 copies (MataChunger) to. The MK-U47 is about 5dB hotter than the C-12s, but even compensating for that, the MK-U47 is a lot noisier (at least 6db) so far. But then again, I was really surprised how quiet the C-12s with Mullard 12AT7 are.

Does anyone have any experience with the 6028/408a tubes? Do they vary much in noise levels? Do they need a long burn in time?

Thanks!
Stefan

I have had very bad yield rate with Ebay 6028 and 408a tubes. . . I recommend buying many copies and then, after finding one pair that is confirmed quiet, I switch one tube at a time for testing subsequent tubes.  Finding the first pair can be a bit random though.