MK-U47 - build thread

Thank you for the test, Inglev! Sounds nice.

Unfortunately there have been a few delays regarding the new batch, but everything's sorted out now and new kits should become available by the end of this week/early next week. Thanks everybody for your patience!

-Max

Fantastic!  I've been watching and ready to pull the trigger as soon as you say they are ready!  Jimi Ray

"My MK-U47 is complete. Did a comparison between the MK-U47 (which has a Thiersch Red Line), a Neumann U47 with a K47, and also my C12 clone (Tim Campbell capsule) and a Neumann M269 thrown in the mix for fun."

I think nr 4 is the C12 with Tims capsule.
Nr 3 is the Neumann M269.
Nr 1 is the Neuman U47.
Nr 2 is the MK-U47.

- Stefan

Hi Everybody,

now that the correct screws finally arrived, I'm completing the assembly of the new MK-U47 batch.
Shipping starts tomorrow, and I'm now open for orders. I'll go through my list, but if you inquired about a kit in the past it doesn't hurt to send me another email.
Kit/pricing and contact info: http://groupdiy.com/index.php?topic=35667.msg437839#msg437839

A quick snapshot during assembly:

Inglev said:

My MK-U47 is complete. Did a comparison between the MK-U47 (which has a Thiersch Red Line), a Neumann U47 with a K47, and also my C12 clone (Tim Campbell capsule) and a Neumann M269 thrown in the mix for fun.

Here's a sample of each microphone:
Mic 1: https://www.dropbox.com/s/ca6uywhw7f355g6/Mic%201.wav?dl=0
Mic 2: https://www.dropbox.com/s/adytkn2rw3lvdm8/Mic%202.wav?dl=0
Mic 3: https://www.dropbox.com/s/hnp82zqm8db11tr/Mic%203.wav?dl=0
Mic 4: https://www.dropbox.com/s/6nja0uu3uugep1l/Mic%204.wav?dl=0

See if you can guess which is which  .

Click to expand...

Thanks for the test! Here's my guess after listening for about one minute...
Mic 1 and 3 sounded the closest to each other, so I will guess this is the U47 and the MK47. Mic 3 sounded more natural than Mic 1, so I will guess Mic 3 is the U47. Mic 1 had a resonance that made it sound not quite as good.

Mic 2 had a more extended top than those two, so I'd guess it's the M269. Mic 4 sounded more scooped in the upper mids, with more treble, so I'll guess it's the C12

You mean the failure of the upper middle? I do not understand the " more scooped".

o3misha said:

You mean the failure of the upper middle? I do not understand the " more scooped".

Click to expand...

Yes, scooped usually means the sound has less energy in the mids frequency range

Ok, thanks for the guesses  .

Behind the secret mic-names are:
Mic 1 = M269
Mic 2 = U47
Mic 3 = MK-U47
Mic 4 = CIY C12

To me, the one that stands out the most is the C12, with a more "smiley mouth" EQ sound than the other 3. I was also surprised to find that the M269 was so similar sounding to the two U47's, even though I thought it was a bit more "closed" or "dull" sounding.

Let me also say that I don't think one mic is better than the other. They all have their own sound character which has its place. On different sources one might come out on top. Actually, just by using a different guitar, you might find you like another mic better.

Cheers

Inglev said:

Ok, thanks for the guesses  .

Behind the secret mic-names are:
Mic 1 = M269
Mic 2 = U47
Mic 3 = MK-U47
Mic 4 = CIY C12

To me, the one that stands out the most is the C12, with a more "smiley mouth" EQ sound than the other 3. I was also surprised to find that the M269 was so similar sounding to the two U47's, even though I thought it was a bit more "closed" or "dull" sounding.

Let me also say that I don't think one mic is better than the other. They all have their own sound character which has its place. On different sources one might come out on top. Actually, just by using a different guitar, you might find you like another mic better.

Cheers

Click to expand...

That is really interesting! Thanks so much for the test. The only one I got right was the C12 haha, and looks like my favorite in this particular instance was the MK-47. Can you provide any details regarding your MK-U47 (which capsule?) and your U47 (all original? K47 or M7?)

EDIT: Sorry, I just revisited your post and saw you already provided those details. Thanks! I was surprised how close the M269 and MK-U47 sound. I found the U47 to sound a little bit brighter than the M269 and MK-U47, but perhaps that is due to the K47. Would love to hear a vocal comparison some time.

also check out the MK-U47 discussions over at realgear: http://realgearonline.com/board/1/pro-audio?q=mk-u47

Testing tubes in my MK-U47.
I have a bunch of WE408a tubes and two JAN 6028, and I can now test them one at a time.
I have replaced the capsule with a 68 pF capacitor and the heater for the unused tube with a 400 ohm resistor pack.
All tubes have been burned-in for at least 72 hours. I'm recording each tube on a separate track in Pro Tools, with the same gain.
First, I leave the mic alone for two minutes, then I tap on the mic,  pick it up and turn it upside down and back again.
So far I'm not impressed by the results.
The main problem is unreliability. Any one of the tubes can work well during a "session". Then I turn the PSU off and let it cool down. When I turn it on again it can be fine, but to often the noise level has gone up and it's acting like a broken tube (hiss, pops and clicks). It's all very random.
Also, when I turn the mic around and upside down (this is the same for all the tubes) I hear "pinging" sounds, like something is moving around or is loose inside the tube.
All the tubes I have tested (I have nine) are very microphonic. Tapping on the microphone house produces a sound almost as loud as when I have the capsule in the mic.
Is this normal for 408a/6028 tubes?
Have anyone tested any other 408a/6028, like the RCA 408a?

Any feedback would be appreciated.

- Stefan

The WEs are the noisiest by far, though do sound good when you get a quiet pair.  I have found RCA, and GE to be very quiet from the get go.  I haven't found the Philips to be particularly noisy either once burned in but the Western Electrics have been problematic with the noise and pops you mention. 

Thank you, Category 5.

Do you have a good sources for the RCA and/or GE tubes?
I have been commissioned to build a MK-U47 for a studio here in Sweden, and I can not deliver the mic with the tubes I have today. They are simply to unreliable. I'm getting a bit desperate... 

- Stefan

stelin said:

Thank you, Category 5.

Do you have a good sources for the RCA and/or GE tubes?
I have been commissioned to build a MK-U47 for a studio here in Sweden, and I can not deliver the mic with the tubes I have today. They are simply to unreliable. I'm getting a bit desperate... 

- Stefan

Click to expand...

Hey Stefan.  I bought all that I could find of the RCA and GE which was not many.  There is a guy selling some NOS GEs on ebay for a decent price.  Not sure where he is located.  I did find the Ericsson tubes to sound good and be quiet, but Kcatthedog got a pair he said were noisy like the WEs.

Are you saying the Philips are too noisy too after burn in?  I haven't had objectionable noise from those yet, at least after burn in.  You might try replacing the heater dropper before you go insane looking for RCAs.  Also, I've notice the need to reset the B+ voltage between tube swaps.  It can change quite a bit from set to set.

Keep in mind that noise performance should improve with both tubes in too, so don't make your final judgement without using the tubes in the mic as planned.  The MKU is not the quietest mic I've ever heard, but it is one of the nicest sounding!

The Philips have more noise than the WEs (in my case), after burn in. One of the Philips have more noise than the other.
The WEs are fine, except that they are unreliable. They can work fine and be very quit for hours, then the next time I turn the mic on they are hissing and spitting at a much higher level (it's not "clean" noise anymore).
It usually happens when I have moved the mic or changed its orientation. The hissing and spitting does not go away after the tube has warmed up. But it might be gone the next time I turn the mic on.
The MK-U47 sounds very fine! I have compared it to a genuine U47 and it's very hard to tell them apart.
The MK-U47 have a bit more noise than the U47, but the noise is (normally) low enough. I just need it to be more "stable".
I will check the heater voltage. If there is any noise coming from the heater dropper I might be able to spot it on the scope.

- Stefan

Max, I received my MK-U47 kit today.  Very nice!!!!  I am still waiting for my Thiersch blue capsule and Tony's (Zayance) next batch of PSU boards, but here is the mic so far:

...and the rear side:

Just recieved my two MK-U47 kits. Can't wait to start building. Pity I have to work tonight.......
They look great, Max!

Waiting for a matched quad of these: http://valvetubes.com/6028-jan-6028-philips-ecg-usa.html Anyone expierences with these?

...these Sylvania GB-408A should be the gold-pinned variant...if they are in fact the same as the RCA gold-pin (visually they are identical), then definately worthy of an inquiry:
http://www.standardradioelec.com/GB-408A