MK-U47 - build thread

[innercityman]

But still active, sorry, I was not attentive

 

[Whoops]

this thread on Gearspace is from 2014

Yes, and it’s still going in 2022, Max last reply was 2 days ago

 

[Bonnie1]

So you pretend that the informations on this page are false, and by the way, dany Bouchard would be a liar ? check this...
https://www.vintagemicrophonepcbkit.com/D-47.html

As per evidence, I try not to pretend anything and only sharing what one knows as fact maintains honesty.

btw, Oliver did introduce the tlm67/87 to U67 mod, 2+ yrs before max (i/o audio) conversion was introduced. Good for Max recognizing Oliver's nice idea and running with it. Also providing the use of lower filament vacuum. ( low upfront investment w/nice return).

 

[martthie_08]

quick little update, I've managed to make some room for the rather bulky Siemens & Halske caps in my MK-U47. Not the prettiest job, but it does the trick and the mic continues to give me goosebumps. It is a bit hard to see on the photo but I made a little aluminum bracket that the two caps are mounted on.

Little fun side note: upon moving the upper tube mount, I noticed that I had the tube filament supply wired on pin 3 of the first 6028 and then took that voltage directly to the second tube, instead of wiring this to pin 4. Must have been by habit from wiring guitar amps... This means that for the last couple years the mic was running on only one of the two tubes with an insane heater voltage - whoops Still this mic got many compliments, especially from Cello and Double Bass players pointing out this mic to have the best sound they had ever heard on their instrument. Needless to say I took the time to correct the wiring and also test out some new tubes I purchased recently (Philipps Miniwatt and Tung Sol 408A).

 

[Greenie]

Hi. Just a question about the DU47 build: Is there a problem to use two 1.5uf 400v caps instead of the 1uf caps?

And what cables are rcommended for this build?

 

[kingkorg]

Hi. Just a question about the DU47 build: Is there a problem to use two 1.5uf 400v caps instead of the 1uf caps?

And what cables are rcommended for this build?

You need to measure the response of the circuit if you use 2x1.5uf. Otherwise you don't know how those will interact with the transformer you are using.

 

[Greenie]

You need to measure the response of the circuit if you use 2x1.5uf. Otherwise you don't know how those will interact with the transformer you are using.

Ok, thanks. I have two 1.5's, but I'll stick to the 1uf then.

 

[kingkorg]

The difference would be in the low end response, varying this cap value could make all sorts of changes in the low end, probably sub sonics, create/reduce resonances. The original value is 0.5uf. I'm not sure why some people blindly "upgrade" this to higher value without checking what it actually does.

The same goes for the high value resistors, and other components. The point is usually to get as close as possible to the original.

 

[chefducuisine]

I am with kingkorg.

Increasing the value of the 0,5 uF Capacitor will lower the low cut-off frequency and as such saturate the transformer earlier. This most likely will generate more distortion.
What you can do if you only have the two 1,5 uF capacitors on hand and get the microphone running closer to spec is to put the two capacitors in series. This will divide the capacity to half of its value (e.g. 2x 1,5uF /2 = 0,75 uF). You will get you much closer to spec... at least until you can access a proper capacitor.

 

[barbaroja]

I assembled this mic years ago and still works like a champ. Just a quick note.

 

[EvLoutonian]

reminded me of this thread: IOaudio Inventor of the parrallel 408a tube configuration in U47 Clone ?

You can see from some of this discussion why Max maybe lost some enthusiasm for this forum, maybe.
(?)

I had a good time building his kits up, and learning a lot from that process.
I just wish I got in a little bit later for the sweet MK-U47 version.
I went for the Equinox bodies, a Cathedral Pipes 'Dale' M7 in one, and Equinox K47 style in the other mic.

 

[martthie_08]

I assembled this mic years ago and still works like a champ. Just a quick note.

same here! still tweaking it from time to time though

next thing I'd like to try is having a foam base under the capsule to absorbing sound to have less reflections within the basket.
Can't find any pictures of original U47 with details on this, anyone?

 

[kingkorg]

same here! still tweaking it from time to time though

next thing I'd like to try is having a foam base under the capsule to absorbing sound to have less reflections within the basket.
Can't find any pictures of original U47 with details on this, anyone?

If using a u47 type body you shouldn't need that for historical accuracy sake, but adding absobing pad at the bottom brings improvements most of the time. You can just try it, and decide for yourself what you like better. The absorbent material here usually controls some unwanted dips/notches in the upper midrange, but can sometimes cause them. So measurements or at least methodicaly, carefully executed a/b tests must be conducted. 1, 2 check, or simple vocal take type of test wont cut it.

 

[studiosteve]

If using a u47 type body you shouldn't need that for historical accuracy sake, but adding absobing pad at the bottom brings improvements most of the time. You can just try it, and decide for yourself what you like better. The absorbent material here usually controls some unwanted dips/notches in the upper midrange, but can sometimes cause them. So measurements or at least methodicaly, carefully executed a/b tests must be conducted. 1, 2 check, or simple vocal take type of test wont cut it.

kingkorg.
That's good info!

What would that absorbing pad be made of? Thanks.

 

[kingkorg]

I use a type of memory foam i got from my physiotherapist, have no idea what it is. Gus suggested once magic eraser, which works nice as well. I even used 3M's yellow earplug type of foam i got from some production scraps. Not too soft, or the waves at that frequency will just go through (typical mic wind/pop filter), to hard the waves will just bounce back and create potentially notch at higher frequency. Experimentation, experimentation, experimentation...

 

[rock soderstrom]

Gus suggested once magic eraser, which works nice as well.

Magic eraser = basotect, a melamin resin foam

 

[tonycamp]

Blast from the past!
I finally broke out my second MKU47 kit! I figured 10 years in a box has been long enough
I modded(ugly style) my first mic years ago to shoe horn in some vitamin Q's, I loved the results so i modded the second one more carefully to do the same, and now will clean up my original, they both have Bluelines and RCA gold tip 408's, I found the most important thing you can do on any of the MK mic builds is keep your high impedance soldering small(no blobs) and clean the heck out of everything with acetone, adhering to this i've had no intermittent noise and very minimal noise floor on the 6 or 7 of these mic builds i've done over the years(original MK47-U has to have the sandbar resistor swapped for a metal chassis resistor), IME they are high quality tools that very much resemble the originals i've used

For slight of hand I put telefunken badges on because why wouldn't I? For even more fun I also put serial numbers on them with the FAF acronyms "fake as fu*k"

 

[tonycamp]

I need the 3 screws for the head basket and the one screw that mounts the body to the bottom bell on the mku47. Got lost somewhere in the shuffle/ anyone know what type of head and what size these screws are? Max you out there?

Hey bro, 8 years later and i lost the screws for my mku47 head basket, did you ever figure out the thread size?
thanx

 

[chefducuisine]

These are slotted countersunk head screws with a slightly raised / rounded head according to DIN964.
https://eshop.wuerth.de/v/senkkopfschraube-m2-5
As an alternative go for stainless steel with a standard slotted countersunk head.

The ones on the basket are M2,5 x 5mm
The one on the bottom bell is an M2 x 5mm

 

[tonycamp]

These are slotted countersunk head screws with a slightly raised / rounded head according to DIN964.
https://eshop.wuerth.de/v/senkkopfschraube-m2-5
As an alternative go for stainless steel with a standard slotted countersunk head.

The ones on the basket are M2,5 x 5mm
The one on the bottom bell is an M2 x 5mm

Thanx so much, saved me a ton of hassle!