MK47 PCB tube mic kit - build thread

[vinylwall]

Hi,
in my case, it was stuck in cardiod mode like Category 5 said. The faulty solder pad was the one of the lower relais pin (see picture)

Hmmmm.  My build is stuck in cardioid too....  :-\

 

[ioaudio]

Check first if your pattern switch is working: It should show 0 Volt in cardioid and B+ (unloaded) or 48v (loaded) in omni position.

 

[vinylwall]

Check first if your pattern switch is working: It should show 0 Volt in cardioid and B+ (unloaded) or 48v (loaded) in omni position.

Got it!  The pattern wire was shorted across to the mic body inside the mic.  This bugger sounds wonderful!  Great job Max!  I'll post pics of my build soon.  Jimi Ray

 

[bach]

My MK47 has a very low output. I have to crank the mic pre all the way up to hear it. The mic seems to sound ok, just really quiet. Pattern switch is working as well.  Anyone having this issue? I've checked my voltage readings with others on this thread and they seem fine to me, but what do y'all think? Here are my voltage readings:

Mic Voltages
37.1V Heater (between heater & dropping resistor)
1.28V Cathode (between 27R & tube)
55.6V Voltage Divider (where 100M, 2M, & 3M resistors meet)
43.3V Before output capacitor IS THIS HIGH?

PSU Voltages
105V Output to mic
48V At pattern switch in cardioid (between 12k & 14K resistor )
30.38V At pattern switch in omni (between 12k & 14K resistor )

 

[ioaudio]

The voltages look Ok.
Re-check all the connections again, did you solder all transformer pins?

 

[bach]

My thought went to the transformer as well.  The kit came with the transformer already soldered in place, but I did re-solder it to make sure the connection was good.  All solder joints visually look good, but I'll see about hitting them with a meter and let you know.
Were the voltages ok?

 

[bach]

Busy Easter weekend, but I was finally able to check continuity on the circuit board pads. Turns out the transformer pad between the large grey 1uF cap and the transformer was bad. I patched a cable between them and now the mic is working like a champ! Sounds pretty great. Plenty of level on the output. I'll give it a go on my acoustic guitar session tomorrow. Thanks for the advice and the circuit design!

 

[vinylwall]

Max!!!  This microphone sounds fabulous!  Great job.  Here are some pics of my build.  Assembled:

 

[vinylwall]

Chunger's MK47 body from China, Philips JAN 6028 NOS tubes, Beesneez M7 capsule (wonderful).  Inside, tube side:

 

[vinylwall]

Inside, transformer side:

 

[vinylwall]

PSU, front:

 

[vinylwall]

PSU, rear:

 

[vinylwall]

Dan's PSU case and Tony's (Zayance) PCB.  PSU, inside:

 

[vinylwall]

Here's a vocal test done with my first MK47 build.  Nice job Max!!!

"Lately":

https://dl.dropboxusercontent.com/u/47755719/JaneyB-Motown/04-Lately%20%28RS2-150127%29.mp3

 

[Timh]

Hey dudes, so I finished my PSU tonight. I'm really happy that it turned on and my LED lit nice and bright, but when I tested b+ it was at ~305 volts. Now, I'm not really familiar with the whole "test load" thing, and I may have even used some incorrect resistors, because my mouser order came with some big 500 ohm resistors (I used the 1K), and then there's the 330 or 680 resistor. I'm somewhat of a newbie, so I went off of Chunger's build because I'm in the US, but maybe I used some European values, I don't know. Am I supposed to have another resistor in there for testing purposes? Did I use the wrong resistor values. I used the 330 and not the 680. I hope I gave enough info. Thanks!

 

[zayance]

Hi There,


Please download the MKPSU docs that i have made available on my WM (1st page).
You'll have your answers there.

Cheers,


T.

 

[Timh]

Did the test load and my 330 and 680 resistors were too low (~130v-115v) so luckily I had an extra 1k and that did the trick.

 

[MicDaddy]

Still hunting for some quiet, good sounding, tubes.

The JAN are in there now, and they are the best sounding noisefloor... however they are so friggin microphonic if a mosquito lands on the body it gives a nasty square wave bzzzzzjjjtjttttt sound. 

I've tried the western electrics, the timbre of these sound nice but the noisefloor is high.

Has anyone seen or tried these? 
http://www.piexx.com/index.php?main_page=product_info&cPath=10&products_id=38&zenid=gtjbkttqbk9gpvvjg9tf68t955

Perhaps I should build a small amplifier jig for testing these more easily.

Appreciate any hints on finding tubes.

 

[MicDaddy]

Finally found some tubes I'm happy with, a few sets.

Now onto the problem of the body itself.

From disassebly, reassebly etc etc over and again, the receiving and screw threads for the two long and one short for the Equianox body have almost completely lost their grip, spinning spinning, now it feels like a cheap China mic.

What I did was replaced the 3 screws with 2x 4-40 sst 1/2"  and 1x 4-40 sst 3/8".  The thread isn't correct but it was just large enough to "bite" into the receiving end.  Now it is holding very nice, and the newer sst screws look nice too.

Don't be cheap about hardware you'll pay in the long run.

 

[laddie.music]

Hey there, 
My name is Prahlad Strickland.
I live in Hawaii and a couple years ago I purchased the IO audio u47 mic kit and Zayance power supply.  I built the mic,  the cable and most of the power supply,  but got stuck on the power supply.  I realised I just don't have the know how to finish and test (safely) the powersupply / mic connection etc.

I would be willing to pay someone $150 to finish this off.

Here is a link to some photos,  as you can see, it's proabbaly over 90% done. Just the last power cables and 105V testing etc...    so long as I have done everything else correct which i'm pretty sure I have.

https://app.box.com/s/rtx5hlw5avobrsk7ozwt2avj9gvsxmbj



I just don't feel comfortable with the rest electrically with power etc...  Let me know if your interested in finishing this off, I would really appreciate it.

I'm pretty sure I used the following wiring
Audio

1 = A- (gray) (connects to pin 3 of XLR at the power supply)
2 = A+ (white) (to pin 2 of XLR at the PS)
Center pin = audio ground (green)  (to pin 1 of XLR)

Power
3 = B- (black [blue in the cable])
4 empty
5 = B+ (red)

Pattern
6 = P (yellow)