Oliver Archut U47-ish mic build

[scott_humphrey]

O.K. I'm sure that there are a million mics that are similar out there, but I couldn't resist showing my build of a U47-style mic.

The circuit is by Oliver Archut:

http://www.tab-funkenwerk.com/sitebuildercontent/sitebuilderfiles/AMIU47alttubeschematic.pdf

Metalwork and transformer are from Oliver. Windscreen is from Blue, obviously. Power supply chassis from eBay.


I've modified the circuit by removing the 29 ohm and the 100 ohm resistors at the cathode. Instead, two 1N4148 diodes are connected directly from the cathode to ground. I compared this to the original circuit and couldn't tell a difference, so I left the diodes since they were in there last. I did not do extensive testing to compare  ...just listened to my voice. The voltages are the same with either circuit. Who knows, maybe I like the "pleasant distortion" from the diodes.

Power Supply


EDIT: images show spam - Jakob E.
EDIT: images deleted - ARdE

 

[baadc0de]

Looking great, thanks for the pics. Russian PIOs at the bottom, no?

 

[scott_humphrey]

Yes, Russian PIO caps below the transformer. Polystyrene on top.

 

[plumsolly]

Looks good! What capsule is that?

Ben

 

[scott_humphrey]

Thanks for the kind words. It's a Neumann K47 capsule.

 

[Jim50hertz]

Very cool build, and nice psu case, can you post a link to it? 

 

[MagnetoSound]

Clever little pattern switching arrangement! 

 

[scott_humphrey]

Clever little pattern switching arrangement! 

Thanks. Coming up with that was the hardest part about building this. The metal piece holding the switch is aluminum roof flashing.

With this configuration the capsule can be easily removed so that it can be set aside in a safe place for changing the tube or repair work. The solder points for the capsule lead are easily accessible once the grill is removed

 

[scott_humphrey]

Very cool build, and nice psu case, can you post a link to it?  

Here ya go:

http://cgi.ebay.com/ws/eBayISAPI.dll?ViewItem&item=130403175420

A word of advice: the panels of this chassis do not make good ground contact with one another. I had to physically remove the paint and add lock washers to make that happen.

The handle on top of the PSU is an extra handle that I had left over from a Par Metal case.

 

[bezen4uk]

Hi,
It's cool realisation!
Diodes instead resistors in cathode network eliminates NFB and makes output impendance a bit lower. Although diode is noisier than resistor, its noise is lower than tube's nois itself.
What is the transformer ratio used for this mic?

 

[desol]

Thanks for the kind words. It's a Neumann K47 capsule.

Hey Scott.. did Neumann sell you the K47? Mind me asking the price?

Cheers.

 

[scott_humphrey]

Neumann will sell you a K47 through one of its distributors. The price may vary depending upon which distributor. In my case it was just less than $800 for the capsule, holder, and screws.

 

[desol]

Ouch, but it is worth it.

Thanks

 

[yoons]

Nice work!
How much did you pay for the body and transformer?

 

[tommypiper]

Thanks for showing us.  I've been eyeing Oliver's 47 bodies for a while, and his BV8s.... did it come with the shockmount?

Good looking, simple DIY PSU board.  What did you use for solder points, are those turrets that you put in the holes for soldering?  Can you tell us where you sourced them?

And that's a very simple easy looking PSU circuit.

 

[zebra50]

Very nice work. Now time to cut some killer tracks with it.

 

[yoons]

OK! I have found the link where you can find kits : http://www.tab-funkenwerk.com/id63.html
This could answer a lot of questions...

 

[scott_humphrey]

Thanks for showing us.  I've been eyeing Oliver's 47 bodies for a while, and his BV8s.... did it come with the shockmount?

Good looking, simple DIY PSU board.  What did you use for solder points, are those turrets that you put in the holes for soldering?  Can you tell us where you sourced them?

And that's a very simple easy looking PSU circuit.

The body did come with the capsule shockmount for the capsule, come to think of it. ...but the screws were not included. I ordered the screws from Neumann. In retrospect, Neumann did not charge me for the screws.

I bought the power supply boards and eyelets fromWatts Tube Audio - http://www.turretboards.com (don't forget to buy the eyelet tool if you decide to go this route).

I did not like the boards that came with Oliver's kit, so I made my own using with boards and eyelets from the Watts store.

The power supply is similar to the G7 power supply (http://www.gyraf.dk/gy_pd/g7/gic.htm), but I've added more RC filtering on the B+. You can see the transformer model numbers in the pictures. Depending on how you wire the B+ transformer you can get a B+ voltage of 105V, but the transformer can also be wired to deliver higher voltage. These same transformers are used on my Ela M251M style mic where the B+ voltage is 120V.

EDIT: deleted one pic - ARdE

 

[geekmacdaddy]

Gorgeous build and documentation. Thank you. I'm following Dany's photo's and I can't understand why he has 6 as ground to the input of the PS, and the cable has ground at 7. Help?
Thank you.