Topic: Using vr-61 ext tubes for 480 into "Actives"

[IowaClint]

Just wondering if anybody has done this.  I have searched the archive and found nothing.  Be pretty sweet to hack the ends off of these and and put 15' of silver clad on them.   
~Clint

[jeromejello]

i belive that the vr-61 is only able to be used with the 460s... just like the other actives... something about an extra contact in the body.

i know nothing..

+t for the idea though... since i imagine 460s could benifit from that idea.

[TNJazz]

There was a post along these lines at one time.  Someone on this board took Schoeps podium mounts and made them into custom actives.  Seems like there were some noise issues that never got resolved?

Anyway, I had this exact idea for a pair of 451's last year, and I got the VR1 tubes and everything.  Called AKG and they told me it couldn't be done but wouldn't tell me why.  Talked to an electrical engineer friend of mine and he looked at it and said it probably wouldn't work either and cited something about noise, distance from the capsule, polarizing voltage, yadda, yadda, yadda.  Wish I knew more about this stuff, but at that point it wasn't worth the effort to continue.

Incidentally, those tubes are VERY solid metal, so it's not as easy as "hacking off the ends".  I couldn't even bend one with brute force.

Dirk

[thegreatgumbino]

http://taperssection.com/index.php?topic=16107.0

[IowaClint]

I am thinking that one of the Hardware /RF engineers at work could help me Isolate the problem.  I am sure it has to be related to the cable type, soldering,  etc....  I think I am going to give it the olde college try. 
~Clint

[thegreatgumbino]

+T for your efforts.  It'd be sweet if it works out.

[johnw]

Here's why it doesn't work:

http://www.akg.com/akg_structuretree/forum/topics//powerslave,_detail,1,id,1196,_language,ENUS,nodeid,4,mynodeid,149.html

Edit: I think someone at SonicSense tried it and got static. But it seems like adding a capacitor might be the solution if all the metal tube does is add capacity. But I am no engineer.  But if someone can make cables for 460s, they will be my hero!

Oh and freelunch tried this with the similar schoeps tubes and has working active cables for his schoeps mics. Maybe he could give it a try?

[TNJazz]

I wonder if this means the capacitor would have to be added on the capsule side though?  Karl mentions the noise being amplified from the cap through the cable.  Seems like adding a capacitor in the body wouldn't have much of an effect.  Then you run into the question of whether or not that's feasible based on the capsule design...

Of course I'm not an engineer so I have no idea.  Sure would be nice though.

Dirk

[it-goes-to-eleven]

Oh and freelunch tried this with the similar schoeps tubes and has working active cables for his schoeps mics. Maybe he could give it a try?

My schoeps actives are working perfectly.. Way on the back burner is an active MG project. But I really like to record more than futz with circuits.  And who wants to screw up a pair pristine $2k matched mics?  So I'm not sure that will happen. Especially once spring hits.

These projects are very time consuming and their is risk.  If you buy one gooseneck for $350 and can't make it work, you have blown the money.  Or if you short the body and mess it up, etc. Then, if you get it working, maybe there are hours of testing and tuning of the circuit for sound quality.

It sounds like some folks are thinking they can just attach the cap to the body with an extension cable.  Nice thought but it won't work.  You need a powered buffer circuit at each end. It is my impression that some AKGs have a FET in the capsule which is capable of driving the cable. It sounds like this series of caps does not.  So that would need to be a part of the design.

[poorlyconditioned]

Oh and freelunch tried this with the similar schoeps tubes and has working active cables for his schoeps mics. Maybe he could give it a try?

My schoeps actives are working perfectly.. Way on the back burner is an active MG project. But I really like to record more than futz with circuits.  And who wants to screw up a pair pristine $2k matched mics?  So I'm not sure that will happen. Especially once spring hits.

These projects are very time consuming and their is risk.  If you buy one gooseneck for $350 and can't make it work, you have blown the money.  Or if you short the body and mess it up, etc. Then, if you get it working, maybe there are hours of testing and tuning of the circuit for sound quality.

It sounds like some folks are thinking they can just attach the cap to the body with an extension cable.  Nice thought but it won't work.  You need a powered buffer circuit at each end. It is my impression that some AKGs have a FET in the capsule which is capable of driving the cable. It sounds like this series of caps does not.  So that would need to be a part of the design.

Exactly.  CK9x series are electrets with the FET built in.  Just run three wires out to a battery box.  You don't even need the bodies!  I've built two sets, one CK91 and one CK93.  Now all I need is CK92

The CK6x are just bare *externally polarized* capsules, so they need: 1) polarization voltage (62V), 2) FET near the capsule.  Both these come from the 460/480 body, or from an "active" connector.

  Richard

[TNJazz]

I've got to think that if it were really just as easy as that someone would have done it by now.  There has to be something else in the equation that would prevent it.  Why would AKG say it's not possible?  They explained to me on the phone a while back why 460's could be used with extension cables and 451's and 480's could not (I didn't understand a word the tech was saying though) so if they would tell me that then why would they not concede that 480's *could possibly* be made to work with a cable system?

I think I've read repeatedly that the 480's lack something to allow for remote powering of capsules.  Maybe therein lies the major limitation?

Dirk

[bluegrass_brad]

the "active" cable for the 460 isnt really active.  It was just an extension cable for the x series capsules, which had the electronics built in and uses an electret style capsule. The 460 body has something that the 450,480's do not which allows them to be used with those cables and capsules. Dont remember the exact details.

[TNJazz]

Right.  A second ring or something in the body that provided that polarizing voltage or something like that.

The CKx series capsules appear to be simply CK1, CK2 and CK3 capsules with an attachment (likely the FET).  I popped the top off one, but I did not dig under the attachment to see what was inside (I only looked at the capsule and the electronics) that were "topside".  They are smaller in diameter than the CK ULS capsules (and the body of the mic too, of course).

The extension cable appears to have a pin that makes contact with the ring in the body (someone told me that's what provides the power) - not sure what's inside this piece either, but it's probably the other half of the equation.

Dirk

[bluegrass_brad]

I may be wrong on this, but if you have the X series capsules supposedly they can be easily powered with a battery box.  This is just something I was told and have never tried it myself. But theoretically it should work since the capsules are the back electret type.

[johnw]

Oh and freelunch tried this with the similar schoeps tubes and has working active cables for his schoeps mics. Maybe he could give it a try?

My schoeps actives are working perfectly.. Way on the back burner is an active MG project. But I really like to record more than futz with circuits.  And who wants to screw up a pair pristine $2k matched mics?  So I'm not sure that will happen. Especially once spring hits.

These projects are very time consuming and their is risk.  If you buy one gooseneck for $350 and can't make it work, you have blown the money.  Or if you short the body and mess it up, etc. Then, if you get it working, maybe there are hours of testing and tuning of the circuit for sound quality.

It sounds like some folks are thinking they can just attach the cap to the body with an extension cable.  Nice thought but it won't work.  You need a powered buffer circuit at each end. It is my impression that some AKGs have a FET in the capsule which is capable of driving the cable. It sounds like this series of caps does not.  So that would need to be a part of the design.

Exactly.  CK9x series are electrets with the FET built in.  Just run three wires out to a battery box.  You don't even need the bodies!  I've built two sets, one CK91 and one CK93.  Now all I need is CK92

The CK6x are just bare *externally polarized* capsules, so they need: 1) polarization voltage (62V), 2) FET near the capsule.  Both these come from the 460/480 body, or from an "active" connector.

  Richard

To be clear, the VR61 and VR62 work with either the 460 or 480 bodies. The VR61 is discontinued and is 12" long. The VR62 is still made and is 3 feet long. The bodies are presumably providing the polzrization voltage the caps need and the tube must have a FET somewhere along the 3 feet.

Why does the tube need to be rigid? Whatever electrical purpose the metal tube is serving should be able to be replaced in the design by something else. For me, even a 3 foot length of flexible material would be great! What is the maximum distance to separate the body from the cap? My A61 angle adapters have no room for electronics, but perhaps they don't need any because the distance the cap is separated from the body is only an inch. I would be willing to chip in money to buy a used 460 body, capsule and tube if someone with the proper background can answer these questions. The VR61 tubes come up all the time on Ebay - a pair just sold for around $100 a week ago. They guy I bought my mics from in 2004 had a ton of VR61s that he was trying to get rid of for $75. I've seen body + cap go for less than $250. In fact there is one on ebay right now that probably won't bring $200 given the cosmetic condition. I'd guess plenty of AKG owners would be interested in finding an answer that explains why you can separate the ck61/62/63 capsule from the 460/480 body with a rigid tube by up to 3 feet, but not with the exact same components in the tube and flexible wiring.