Topic: My "homemade" AKG CK91 actives, work with AT8531 phantom adapter!

[poorlyconditioned]

I'm been fluffing my AKG CK91 "homemade" actives several places in this forum.  (www.cs.uwaterloo.ca/~mannr/AKG)  The main reason I did this was stealth, but also for cost reasons.  I don't buy the bodies, just the caps.  Right now I've got two pairs of caps, CK91 (cards) and CK93 (hypers).

Since these are electret capsules and the FETs are right inside the capsule, these are really easy to build.  Just solder three wires inside the capsule and ran a cable out to a 3-pin miniXLR plug.  Then I started building battery boxes for these following the suggestions from AKG tech support.  (The schematics are in the URL above.)

Well, I just discovered that the Audio Technica power modules (AT8531, etc) will power these mics.  I just plug an XLR connector to my preamp, my miniXLR connector into the AT8531 and turn on phantom power.  Works great!  Just make sure to wire the capsules correctly to the miniXLR.

  Richard

[willndmb]

i still am lost as to how you do this, and where to begin
but i am impressed +t

[cybermansrev]

Yet again you come through with another exciting project!
Now I can see another use for the 3 wire BBox I made to your design.
Here's the very first ticket I can give. +T

PS Does the CK-61 sound as good with the 3 wire battery box as with AKG bodies?

[jeromejello]

PS Does the CK-61 sound as good with the 3 wire battery box as with AKG bodies?

fwiw, these are the ck91's for the 39x blue line series.

[cybermansrev]

Oops sorry had CK61's on my mind for some reason, yes CK91

[rowjimmytour]

Could ya wire a normal XLR cable and plug into UA5 with out any thing in the middle?
+t for the project
Peace
 

[poorlyconditioned]

Could ya wire a normal XLR cable and plug into UA5 with out any thing in the middle?
+t for the project
Peace
 

There are two ways to power the CK91/2/3 capsules:

poorlyconditioned 3-wire battery box (miniXLRM socket) > (miniXLRF plug) cable to CK91
UA5 (XLRF socket) > (XLRM socket) AT8531 power adapter (miniXLRM socket) > (miniXLRF plug) cable to CK91

My guess is that the original SE300 body is better than the AT8531 power adapter.  I would use the body if I had it, but I didn't want to pay for it.

  Richard

[JasonR]

Just as an aside, the Sonosax SX-M2/LS is said to power these caps as well, at least in the French version of the owners manual.  Makes me wonder how hard it would be to setup something similar to what you've done for the Schoeps or Neumann 100 series caps.

- Jason

[poorlyconditioned]

Just as an aside, the Sonosax SX-M2/LS is said to power these caps as well, at least in the French version of the owners manual.  Makes me wonder how hard it would be to setup something similar to what you've done for the Schoeps or Neumann 100 series caps.

- Jason

I'm pretty sure the Schoeps and Neumann are externally polarized.  Like the AKG CK6x series, these need 62V to the capsule.  From the Scheops documentation it looks like the active heads actually have four wires going to them: ground, +62V (polarize the cap), +9V or so (for the FET), and audio return.   All are inside that active cable!

To drive these the system would need a 62V generator in the box, and an additional FET, *right at the capsule* (built into the connector).  As far as I know, this is what the "Nbox", "Rbox", "jk_labs", etc all do.  But I'm happy to see pictures of the guts if anyone has them!

I'm thinking about building a set of actives, but not right away.  I hope someone will get to it before me.  My next project is to build some more preamps.  Oh yeah, I'm going to go to some more shows and drink some beer too

Hey, while we all ponder this, does anyone out there have any mechanical expertise?  In particular, could you tell me what thread is on the AKG CK6x caps?  Half of the battle is getting a good connection to the capsule, just an inch or so of aluminum or copper pipe with the exact thread on it to mate with the AKG caps.  Then figure out some spring-type mechanism to reliably contact with the center pin.  Perhaps mimic what is in the 460/480 body.  The second half of the battle is to get a reliable battery operated 62V power source (oscillator/voltage multiplier/charge pump).  After this is very easy to build the appropriate circuit.

  Richard

[JasonR]

Here's a rough schematic of the Schoeps KC5 active cables.  The 3-pin (plus shield) Lemo connectors are added for compatibility with the Sonosax SX-M2/LS.

Is that circuitry (on the left) the additional FET?  If so, I wonder if you have any idea how I'd wire these to work with a simple battery box.  Might be a nice stealthier alternative.

Thanks!
- Jason

[poorlyconditioned]

Here's a rough schematic of the Schoeps KC5 active cables.  The 3-pin (plus shield) Lemo connectors are added for compatibility with the Sonosax SX-M2/LS.

Is that circuitry (on the left) the additional FET?  If so, I wonder if you have any idea how I'd wire these to work with a simple battery box.  Might be a nice stealthier alternative.

Thanks!
- Jason

Thanks (and plusT) for the Scheops doc.  I've seen that before (micbuilders group on Yahoo, I think).

CORRECTED.  I better get a look at the Scheops gear before making claims.

I *think* the FET is at the end of the "active cable", and the capsule is just a bare element.  But I'm not sure.  Can anyone confirm this?

I know that AKG CK61/2/3 are caps are just bare elements (without the FET).

Anyway, time for bed now...

 Richard

[JasonR]

If I'm reading the schematic correctly, Q1 is a FET on the capsule end of the active cable.  I'm fairly confident that this information is accurate since the evaluation was done by Bill Drucklieb on my equipment so he could properly modify my KC5 cables for the SX-M2/LS.

- Jason

[thegreatgumbino]

Hey, while we all ponder this, does anyone out there have any mechanical expertise?  In particular, could you tell me what thread is on the AKG CK6x caps? 

Isn't this info listed on the product sheets as m19 x 0.75 thread?

[Laurent]

Would an AT8533 or a Samson PM-4 power the caps also? I thought it was quite the same as the AT8531...

[poorlyconditioned]

Would an AT8533 or a Samson PM-4 power the caps also? I thought it was quite the same as the AT8531...

Probably.  But you'll have to try it and see...

  Richard