MK47 PCB tube mic kit - build thread

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maybe an obvious question , but it came up when building the PS .

am i right when i say that the mics equivalent DC resistance is actually 2K11 ohm ?
12k then should be the approximate coil resistance of the relais ?
 
Another PSU question...

The choke is 500 ohms. Should the overall resistance between the first two caps be 500 or 1000 ohms?  It was mentioned at one point that you could use two chokes in series since they were affordable. The alternate resistor shown on the schematic is 1000 ohms.

If using only one choke, should I add a 500 ohm 5w resistor in series? Or does it matter if I can adjust the voltage later in the circuit?

Thanks! 
 
bobine said:
If using only one choke, should I add a 500 ohm 5w resistor in series? Or does it matter if I can adjust the voltage later in the circuit?

Depends of what your transformer puts out.

Mine gives a little less than 200 Volts and I had to use 500Ohms all the way.
 
Success!  Stable.

This is the large Hammond case 513-0900
The Triad VPT230-110 transformer

The test load is a little low, so my test output voltage should run about 108.5 if the mic load is actually 2300.

Thanks to all who've contributed!

 

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Is there an ideal or a standard pinout recommended for 7-pin connectors on this project?  Should there be?

thx


 
Kingston said:
7 pins? You only need 5... Might be able to even gamble with just 4 if you skip shield wire.

True.  But many will be using Skylar's EQU47 body, which is fitted with a 7-pin Binder connector.

This post suggests there are no pinout conventions for tube microphone cables.
http://www.groupdiy.com/index.php?topic=41399.0

Looking at the U47 schematic (6-pin):
1,2  audio
5  105v
3,4,6  0V ground
http://www.gyraf.dk/gy_pd/g7/gic_s.gif

In one of Gyraf's mics (7-pin):
1  0v ground
2  +v
3,4  +/- audio
5 pattern
http://www.gyraf.dk/gy_pd/g7/gic_s.gif

Any interest in having standard pinouts for this mic with 7-pin connectors?

Any advantages to one config over another?  Maybe it would be nice to have a published standard for interchangability or if one of the White Market shops wants to supply a PSU or cable. Maybe it doesn't matter. 

 
 
There so many options and connectors that there cannot be an 'official' standard.

I guess the best bet is to follow the Neumann way... Binder 7-pin are compatible with the old Tuchell connectors used in U67, M249, and the likes...

1-2 audio
3 ground
4 heater
5 B+
6 option (remote control pattern or measuring input)
7 chassis ground

Axel
 
bumping this thread up again
;D finished my mk47 (with a Dale M7 until the beezneez arrive)
no crackling or popping as described before.
pretty straight forward , turned it on and worked.
my 1K / 5 Watt resistors in the PS get rather fast quite hot though ,
i guess i'll change them to 10Watt ?
didn't use a pot in the PS . used a resistor with trial and error to get the 105Volt (at least in the evening , midday when everybody starts cooking , voltage drops to 103 , but that's 2% to 3% )
lost my camera so i'll  post pics when i can lend one.
for the start 2 pics of the bottom with the resistor mounted , and the rails
DSCN0087.jpg

DSCN0084.jpg
 
nashkato said:
bumping this thread up again
;D finished my mk47 (with a Dale M7 until the beezneez arrive)
no crackling or popping as described before.
pretty straight forward , turned it on and worked.
my 1K / 5 Watt resistors in the PS get rather fast quite hot though ,
i guess i'll change them to 10Watt ?
didn't use a pot in the PS . used a resistor with trial and error to get the 105Volt (at least in the evening , midday when everybody starts cooking , voltage drops to 103 , but that's 2% to 3% )
lost my camera so i'll  post pics when i can lend one.
for the start 2 pics of the bottom with the resistor mounted , and the rails
DSCN0087.jpg

DSCN0084.jpg

Cool, congrats on the build, sound good?  Need I ask?  ;D
 
PSU related question......This maybe silly question .....Can voltage regulator tubes be used in mic psu ? did I read to add noise ?.....I have some transformers with 250VAC output was thinking of using VR105 regulator

If this is silly idea let me know so I can learn thanks.....
 
many ways to build the PSU - passive with/out choke, aktive with tip pass transistors, tl783 + additional filter, a tube regulated version would be a nice addition :)

BTW, FIY - new batch is ready to ship and a few kits are still available, pls check the white market section.

-max
 
Thanks Max  take you have got my payment now cheers, looking forward to my kit cant wait....
i'll look into the Tube regulators for PSU....i'll have to go read n learn and ask questions....

Max yr PSU looks great and easy to make its just I have couple larger transformers and chokes & tube regulators laying around here and would like to put them to good use (if workable) and so save a little money for a lovely capsule.

Cheers.
 
For the AC transformer, will the one from Edcor for the MK7 work?

120V 60HZ primary
Dual secondary
160VAC @10MA
12VAC @500MA

Also, are Thiersch and Beezneez the only places to get a capsule mount from?
 
Received my kit yesterday and built immediately!
Thanks Max, all the parts and board seem of the highest quality - a pleasure to work with and a great design all-round.
Desperately awaiting my Beez-neez order now, guess I can get a PSU together in the meantime...
(apologies for bad cameraphone photo - also dont worry I havent soldered the big resistor)
mk472.jpg
 
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