MK47 PCB tube mic kit - build thread

[kante1603]

looks very good mate (although photos are now down!)
i have also bought a t bone 700 for this purpose. do you have any hints/particular issues i should look out for? Did you use the psu case that comes with the t bone?

Hello Joe,
thanks for the compliment.I´m really sorry that the photos are gone,I´ll try to upluad them as soon as possible (having an issue at imageshack at the moment-I´ve lost all(!!!) of my photographs there and I don´t know why.But they are all here on my drives so I can bring them back again,piece by piece which will be a lot of work and waiting :'(

O.K.,about the t-bone:There´s less space inside than for example in skylars mic body but it works pretty well.Max´s guide for assembly is very good and I did it the same way.
You will have to be carefull with the small screws-these are weak,so use a very good fitting screwdriver and take some patience.
The big cap I had was fitted with holders having mounting holes at its sides-it is easy to remove them and just file them.
Also I had to slightly widen up the mounting holes on the pcb (with a small drill)-easy job.
I especially like the tube because it is made of steel and easy to sand and laquer.It´s a good conductor from bottom to top and shielding is super-fine.
Don´t know what capsule you will use,I have a Thiersch.I had to use the smallest holder I was able to get;after that the position was nearly exactly as in the original-cool!
About the psu:I used a modushop case;the model is called "Galaxy  Maggiorato",the type I used is "GX-187".Here some links:
http://www.modu.it/frontale_nero.jpg
http://www.modushop.biz/ecommerce/cat037_l2.php?n=1#3
the t-bone housing is much too small thinking about putting in a pcb,a potentiometer,a choke (i used the Triad) and a torroid and taking care of good ventilation (parts on the pcb get pretty hot!).
Apart from all of that I needed a certain amount of super-glue to fix the "flightcase" aluminium-profiles;now it´s fine.
The included shockmount is pretty good,but the cable is bull***t;mine was soldered very bad and had partly missing isolation/shrink tubes.
So I built new ones because the connectors where very cheap ones too.Now I have neutriks.

Conclusio:The t-bone set contains a lot of usefull things and is absolutely worth the money (it´s 149,-Euros here including shipping),getting a case plus shockmount is fantastic...therefore i started to build a second of those babies-putting in a "real" microphone is a lot of fun;the result is an awesome sounding mic.

Well,i think that was all for the moment,hope to have helped,

best regards from germany,

Udo.

P.S.:Here some pics again:










Edit:Case-type corrected to "GX-187".Pics added.

 

[JoeMorris]

Thanks for your info Udo,
Should be most useful for my own build, which I hope is as successful as yours! I havent built the psu innards yet but imagined theyd probably be too big for that little psu case, would have been handy though! I am due to have the Beez-neez capsule from the groupbuy (if it ever arrives!) so am a little concerned about the capsule mount I'll get with it now, as I doubt it will be a small one...

 

[idylldon]

I thought I'd share some pics of my finished build.  Needless to say, I'm ecstatic about how this mic sounds and looks.  I'm debating about building another one because this one sounds so great.







The PS case has a nice lid that covers the switches, test points, and voltage adjust knob.  When on, the PS is damn near bulletproof.  I love finding these old cases and putting them back in to use.

BTW, my mic has the Bees Neez group-buy capsule and it was well worth the wait.

Cheers,
--
Don

 

[mrcase]

Uhhh. Nice build. Love it. great idea putting the test points for the voltage on the panel. what kind of connectors are those?

cheers
martin

 

[idylldon]

Uhhh. Nice build. Love it. great idea putting the test points for the voltage on the panel. what kind of connectors are those?

cheers
martin

Thanks!  They're actually test jacks that I got from my father-in-law when he was cleaning out his garage.  He was a physicist at Hughes and had collected a lot of electronic stuff over the years.  When he moved, I inherited all of it.  These hold the regular diameter probe tips tightly and have a bit of a retro look to them because . . . well . . . they are old.  I used some on my PM670 build as well to make those voltage adjustments easier.

Cheers,
--
Don

 

[kante1603]

Hi Don,

congrats to your build-very well done,I love this very robust style.
Good idea putting testing pot and measuring points to the outside with the ability to cover it.

Thumbs,

Udo.

 

[Winetree]

Got some new tubes. Finally got a pair to work and have  both mics working. Sound Great.
Still having problems with the patterns. Have wired the switch  2 ways and still no true omni.
Only switches front sides of capsule. Omni should turn on both sides. I know I've asked this question 2 times before but what is the correct way to wire up the Pattern switch.
A diagram using the schematic would be best.
Also,  I notice a little difference in gain and sound. Because I don't have a tube tester, I picked any 2-6028's tubes for the two mics.  Would it make a difference to purchase 4 matched tubes for the 2 mics to sound the same.

 

[idylldon]

A diagram using the schematic would be best.

Basically, you just want to be able to switch from the end of the 14K resistor to either the 12K resistor or the pattern terminal.

Cheers,
--
Don

 

[Winetree]

Thanks, I'm sure the diagram will help many. That's the way I have it hooked up.
When I flip the switch, I just changes the dominate side to the back side.
Shouldn't both sides be almost equal in volume when in omni?

 

[crackerzot]

Shouldn't both sides be almost equal in volume when in omni?

No, later U47's addressed this issue, but the earlier U47's  had a discernible drop in overall level when splitting to both sides of the diaphragm.  A level drop is normal operation with these kits when in omni mode.

 

[Sredna]

What´s the difference in circuit between early and late U47´s?

 

[etiefenthaler]

Hi,
could you recommend a spdt switch for pattern control and test switch?

thanks a lot
Erich

 

[crackerzot]

What´s the difference in circuit between early and late U47´s?

Sorry for the tardy reply...  I can't recall with specificity what Neumann did, but something was added to the circuit so that the gain would be brought back to the same level in omni as it was in cardio.  I remember reading about this in a fairly in depth article about U47's not too long ago.

As a small aside, and a shameless plug, I thought some might be interested to know that the M47 kit is being used in a worldwide theatrical promotion campaign right now for the new Disney film "Winnie The Pooh", on commercials now airing worldwide.  I voiced all the commercials that are being aired on radio and TV with my new mic. 

 

[androidtube]

Sorry guys, is surely already been said, the transformer may be good that you can see the link for the PSU power? Thanks 

http://www.tube-town.net/ttstore/product_info.php/info/p2192_Ringkern-Netztrafo-30VA-Preamp.html

Best

Anthony

 

[kante1603]

Sorry guys, is surely already been said, the transformer may be good that you can see the link for the PSU power? Thanks 

http://www.tube-town.net/ttstore/product_info.php/info/p2192_Ringkern-Netztrafo-30VA-Preamp.html

Best

Anthony

Hello Anthony,

yes-it´s a perfect match.I used them on my builds taking the 230v primary (we´re in germany) and the 200v secondary so you can build it right after max´s schematics.Also there´s an 6.3v secondary;I took it to drive a very nice Fender jewellamp for "power on".

Hope to have helped,

have fun,

Udo

 

[androidtube]

Hi Udo, thanks for your answer, I is been very helpful. 

 

[EEMO1]

how do I find out which alternative choke to triad would be usable?

i've been looking at this Hammond 157J choke (10H, 65mA, 205ohm, Max oper. voltage 400V).

the resistance is different to the triad and so I need to calculate a series resistor to match the resistance of the choke-resistor in parallel on the scematic?

right?

 

[Kingston]

that choke will work fine. all you need to do is add the difference of resistance to the next 1k resistor. triad is 500 ohm, hammond is 200. That makes the next resistor in line 1k3. or thereabouts.

 

[rascalseven]

Any USA sources for a 200vac 100mA power transformer for this psu?

I'm talking with Edcor about a simple, open frame psu transformer with these specs, and they can do, but I'm not gonna hassle with them if there is something off-the-shelf somewhere else (unless it's prohibitively expensive).

If there isn't something immediately available, then how about a group buy?  If interested in organizing a group buy please email me at r7fm (at) tx (dot) rr (dot) com, and let me know.  If there's interest, I may move forward.

Peace,

JC

 

[rascalseven]

Just answered my own question 

http://www.antekinc.com/details.php?p=603

Has 6.3v taps, but they can just be ignored.  The current rating and price are quite good.

JC