The AKG Actives Project

[Todd R]

Thanks, Richard!  That makes sense.

grider -- no, I've got no knobs on my ECMS.  As I said, no gain in our traditional sense.  It probably has the FET and line drivers Richard mentions (and it sends a balanced signal).

[willndmb]

thanks for the input todd and tim
i ment to say a large difference in sound would sway me one way or the other
with that said i have heard a decent amount of jklab akg recordings and can't tell much difference between them and ones with full bodies
i never really saw a box live and payed much attn to it, but from the looks of it with the AA Battery next to it, its much smaller then i imagined, which is a good thing

again huge props to richard for his work as well

[OFOTD]

Just a bit of caution here with this project as I know several folks working on several different options for the AKG capsules. 

If you are looking for an active solution that will sound just like your 480's it is not going to happen.  If you want something that has a familiar AKG sound then yes that is attainable but not an exact copy.   

[BJ]

Mic bodies don't provide gain in the typical sense.  They merely buffer/strengthen the existing signal so it can drive a balanced cable and a low impedance preamp input.  There are typically two buffers in the mic body.  The first is the FET (field effect transistor) right at the capsule.  This strengthens the extremely weak signal from the capsule.  The second is the a line driver transistor(s) or a transformer, or both.  This drives the balanced cable.

What I am doing is the former only, ie., the FET.  There is no line driver and certainly no preamp.  The output impedance will be high (eg., 10k), just like the battery boxes we all use for electret mics.

I'll leave it up to others if they want to add stuff, either a line driver or a preamp stage.

  Richard

Richard...rock on man....unbelievable work.

the bold part above....is that what the box is that tim linked?  and then the cap in the pictures is what richard has given the schematics too? 

thanx guys

[poorlyconditioned]

OK, I got a prototype working!!!

The "wooshing/scratching" noise was due to a poor connection to the mic capsule.  Now I can hear everything loud and clear and there is no hum or other noise.  Just a bit of self-noise, probably due to my preamp (my Minidisc!).

So, now I have the parts soldered to a (very small) circuit board and inside the collette.  Next I have to encase the whole thing in epoxy, and build a battery box on the other end.  I'll probably have to do some adjustments to make sure the FET is "centered" on the right voltage for optimal response.  But it is looking great so far.

I'll return to this next week...

  Richard

[Chuck]

OK, I got a prototype working!!!

The "wooshing/scratching" noise was due to a poor connection to the mic capsule.  Now I can hear everything loud and clear and there is no hum or other noise.  Just a bit of self-noise, probably due to my preamp (my Minidisc!).

So, now I have the parts soldered to a (very small) circuit board and inside the collette.  Next I have to encase the whole thing in epoxy, and build a battery box on the other end.  I'll probably have to do some adjustments to make sure the FET is "centered" on the right voltage for optimal response.  But it is looking great so far.

I'll return to this next week...

  Richard

I wonder about stuff like the way the capsules connect to the collettes. That connection could be difficult to make work correctly and present to be a problem. It seems most every mic manufacturer has their own way to ensure good contact. Also, is the capsule/ collette junction a part of the resonator or, is all that "tuning" done in the capsule?

I for one am psyched about this! Thanks a bunch Richard! +T

[fozzy]

OK, I got a prototype working!!!

The "wooshing/scratching" noise was due to a poor connection to the mic capsule.  Now I can hear everything loud and clear and there is no hum or other noise.  Just a bit of self-noise, probably due to my preamp (my Minidisc!).

So, now I have the parts soldered to a (very small) circuit board and inside the collette.  Next I have to encase the whole thing in epoxy, and build a battery box on the other end.  I'll probably have to do some adjustments to make sure the FET is "centered" on the right voltage for optimal response.  But it is looking great so far.

I'll return to this next week...

  Richard

Were you able to get it onto a single layer of a circuit board (even if you had to use both sides) rather than a couple of layers

[JNT]

Great work Richard.  +T

Joe

[F.O.Bean]

Great work Richard.  +T

Joe

agreed, awesome bro!

[poorlyconditioned]

OK, I'm still stuck on the mechanical issues.

In particular, I need a good way to connect to the center pin of the capsule.  Does anyone know how the JKlabs ones are done?  I tried a 1mm crimp, from a DB25 type computer cable, but this is not reliable.  I need something that I can embed in epoxy at the end of the collette.

I'm *almost* ready to just hard wire/solder/glue-tape my stuff right next to the cable.

Also, I'll probably be taking a break from this due to classes starting and also some more shows to tape in the fall.

So, any mechanical solutions, post here or PM.

Thanks,
  Richard

[Charlies]

I now have a digital camera and can take some pics of my JK box. If that would help, let me know. This is the box with adjustable gain versus fixed/no gain.

Charlie

[Todd R]

As I recall, the active head on my JKLabs setup has a very small metal tube attached upright to a round piece of circuit board material and permanently epoxied inside the head/colette.  The ck6x capsule pin inserts into the center of this small tube when the capsule is screwed on.

I'm pretty sure there are pictures of the inside of the active heads that were posted along with pics of the rest of my JKLabs system.  I think the links to the thread with these pics is somewhere earlier in this thread.

[grider]

I now have a digital camera and can take some pics of my JK box. If that would help, let me know. This is the box with adjustable gain versus fixed/no gain.

Charlie

I can do the same for my 460>ck1x equipment

[poorlyconditioned]

I now have a digital camera and can take some pics of my JK box. If that would help, let me know. This is the box with adjustable gain versus fixed/no gain.

Charlie

I can do the same for my 460>ck1x equipment

Thanks for the offers guys.  If you get a chance, I'd really like to understand how that center pin is fitted.  There seem to be two possibilities.  One is to have a socket to fit it, and push just a little bit up.  There is some spring in the pin.  Another way it to have a crimp of some sort in the socket.

Anyway, I got fed up last night and just hardwired to the capsule.  I guess it was the medication () I took, made me see things in a new light .  All I did was wedge a thin copper wire between the capsule metal and the plastic insert.  That connects to the body. I put another wire under the nut that holds the center pin.  In the process I clumsily dissassembled the capsule.  There is really not much there at all!  Just a gold (?) diaphragm, a backplate with holes, and some kind of opening in the back.  This is a single unit mounted on plastic, soldered to a spring, plus a metal sheet/grille in the front of the capsule, and a separator ring.

Anyway, all the parts near the capsule are worth $20 max, so I'm just going to glue-tape it up and cover wth copper foil.

I'll report with gruesome pics in a few weeks.

  Richard

[aberg]

I now have a digital camera and can take some pics of my JK box. If that would help, let me know. This is the box with adjustable gain versus fixed/no gain.

Charlie

I can do the same for my 460>ck1x equipment

Thanks for the offers guys.  If you get a chance, I'd really like to understand how that center pin is fitted.  There seem to be two possibilities.  One is to have a socket to fit it, and push just a little bit up.  There is some spring in the pin.  Another way it to have a crimp of some sort in the socket.

Anyway, I got fed up last night and just hardwired to the capsule.  I guess it was the medication () I took, made me see things in a new light .  All I did was wedge a thin copper wire between the capsule metal and the plastic insert.  That connects to the body. I put another wire under the nut that holds the center pin.  In the process I clumsily dissassembled the capsule.  There is really not much there at all!  Just a gold (?) diaphragm, a backplate with holes, and some kind of opening in the back.  This is a single unit mounted on plastic, soldered to a spring, plus a metal sheet/grille in the front of the capsule, and a separator ring.

Anyway, all the parts near the capsule are worth $20 max, so I'm just going to glue-tape it up and cover wth copper foil.

I'll report with gruesome pics in a few weeks.

  Richard

Wow, you've got balls man... taking apart a brand new cap like that.... good work!