DIY U-47 from Cascade M20U

[fum]

CJ,

drop me a line at:

sales  at shinybox.com

ju

 

[kato]

I'm in on this just cuz it's stupid unique, cheap, and I have a pawn shop akg condenser that needs all the help it can get.  I just ordered the parts. $2.96, not including tube and transformer. It won't look as cool without all the vintage german parts. But it's a fun experiment.

you must use the 48 right off the supply, not after  5.11 k resistors

I was just gonna make a dedicated clean 60v external supply and do the same jugular tap you did.  But I suppose a straight 3 pin xlr setup would be more studio portable.  I'm not sure how to do it.

Dumb q coming. Bear with me.  With phantom 48v on pins 2 and 3, do I just pick one? 
Pin 1 as phantom ground, pin 3 for 48v, and nothing with pin 2?

 

[CJ]

if you only use one preamp with the mic, you can modify it for the mic,

but you have to make sure that there is no path to ground thru the transformer sec in the mic or preamp, in other words, balanced on both sides with no center-tap connection to ground,

that is why i use the pwr supply connector,

i save un racking and soldering a bunch of preamps,

i figure that this is a studio mic, not a road mic, so looks are not an issue,

 

[kato]

By "studio portable" I mean switching preamps and rooms without a tethered PSU. That'd be easier. But if it won't sound its best with an anemic 48.  47v... 46v... and not enough mA, then a dedicated PSU it is.

Thanks again CJ for sharing your design.  It's too cool.
I always wanted to try Analag's mic circuit, but I couldn't find a capsule that could handle the 80v so I'm glad to have a distinctive design I can make happen.

 

[kato]

I was all naively excited thinking I could build a PSU in one day. Ha!

Nevertheless, one week later, it's built.  In a spare, extra-large stompbox enclosure.
It's dialed in at 56v.  Good for about 0.3A I figure.
Time to start on the mic...  Anyone else in on this?  Pasarski?

 

[marcus4audio]

we need a BV-08, plus maybe some more bass, so we can wind 2600 turns and 400 turns on some 31 UI with a stack good for 750 henries instead of 150 like the stock version

Hi CJ, I really enjoyed reading this. BTW, you mentioned that original BV08 has 150H inductance. Did you measure the original or you just follow the info from AMI site? Also, 150H at 100, 200 or maybe 400 hz???

 

[shabtek]

where is that CJ?

 

[jackies]

I been waiting for him to continue his monumental 670 project...

 

[kato]

How or what is the "CJ?" 

 

[gyraf]

yes, indeed - what is it?

 

[CJ]

been doing a DIY tile job for the first time,

gotta know your mortar, your grout, your hardy backer board, your grout sealer, your tile saw,

but it came out great so back to transformers,

 

[okgb]

Georg ?

 

[kato]

I found a box among my unfinished projects labeled "Vacuum Brain CJ47."

Inside was a gutted AKG Perception, a home-etched board, a bunch of resistors, and a sub-mini Raytheon tube.

I think this is from 2013, still unfinished. I was such a newb then, (still am,) I'm not even sure this would work. But dang, at this point I might as well build it and see.

One thing for sure, I'd need a different body. There's no way a transformer will fit in there.



Thanks for letting me necrobump.

 

[kato]

Here's my overlay if anyone feels like checking my work.

There are pads around the middle for jacking in 48v from a separate supply.

CJ had an insulated turret at the butt end of R1 (not at the backplate connection where I'd expect.) Would that be necessary?

I'm thinking the 3w / 2w resistor designations got transferred over from the original Georg version, and probably aren't required in the 48v version.

Gurus? Anything drastically wrong here? Is CJ still around these parts?

What IS the CJ??