Topic: Experimental 'umbilical cable' for C460 to CKxx capsules

[groovon]

This might be an off-the-wall idea, but I've collected and/or made the parts to make 'umbilicals' for a couple of my C460s, as an experiment. (And of course without irreversably changing my beloved mics.)

But will it work?

And if so, how long a cable do you think I can get away with? It will of course be carrying a super low-level, unbalanced signal. Shielded, but will probably be quite high in capacitance, as it will be of small diameter. I'm thinking three, maybe four feet might be OK.

Whaddya reckon?

Dave

[groovon]

Right, of course. I will not go too small dia., or too long. Even a couple of feet extension would be useful.

[groovon]

CATV coax? Yeah, but try hiding a length of that in your hat!!

You're probably right though, I'm already thinking that even a foot or so would probably play havoc with the freq response.

Well, even a few inches of flexible extension gives the possibility of mounting the caps at an angle to the bodies, and I'm still interested in it as an experiment. (I've actually got a pair of A61 angle adaptors, but they're in storage at the moment and not accessible.)

Dave

[groovon]

Sorry to say (but as I might have guessed), this experiment was a dead loss. S/n ratio went out the window even with a short length of RG-58 RF cable. The small amount of cable capacitance was enough to suck the life out of the cap's output.

I have to put a hold on this project until I have time to make buffers or preamps and find suitable hardware. Maybe it exists somewhere. I know I'm not the only AGKer with this fantasy.

I'd welcome any other ideas, or anything you find relating to this topic. Especially of the DIY sort. Please post links(!)

PS - Ha-ha! I wrote this before I ever heard of the 'AKG Active Project'. All I can say is, Good Luck y'all!

Cheers
Dave

[Walstib62]

What parts did you get? Are you using threaded tubing to attach to the caps?

[groovon]

No, apart from the 1mm gold-plated pins it's all pretty makeshift so far. First experiment I tried 2 feet of RG-58 coax through ground-down plastic wine corks, the shield sandwiched against the cap threads by the corks. Lost most of the cap's signal through cable capacitance! Verdict: naked mic capsules need a buffer/impedance converter to drive a cable. But we already knew that, right? 

Dave

[Walstib62]

Yep. Gotta have the FET circuit right there at the cap. Theoretically, any condensor mic could have this type of cable.

[groovon]

Yes, 'theoretically'!

There is much wishful thinking going on on this subject! "Just stick an FET in there and Bob's yer uncle!"

Right. 'Easy' to make a CK6x cap sound like a $20 Radio Shack lapel mic.

Schoeps, AKG spend millions on R & D and have reputations to consider. They don't allow anything out that will sound like crap. So maybe there's a reason why AKG C460B/ULS system mics are the way they are, without 'active (true condenser) caps'. I'm just sayin'.

The reality is, even from a skilled amateur's workbench, it will not happen without some loss of signal-to-noise ratio and degradation or change in quality. Even the high-end R&D'd-up-the-wazoo remote/active caps can't be as good or as quiet as the same company's best all-of-a-piece studio mics.

It's fun trying, though... long as the wishful thinking lasts(!)

Dave  8>)

[Walstib62]

Yes, 'theoretically'!

There is much wishful thinking going on on this subject! "Just stick an FET in there and Bob's yer uncle!"

Right. 'Easy' to make a CK6x cap sound like a $20 Radio Shack lapel mic.

Schoeps, AKG spend millions on R & D and have reputations to consider. They don't allow anything out that will sound like crap. So maybe there's a reason why AKG C460B/ULS system mics are the way they are, without 'active (true condenser) caps'. I'm just sayin'.

The reality is, even from a skilled amateur's workbench, it will not happen without some loss of signal-to-noise ratio and degradation or change in quality. Even the high-end R&D'd-up-the-wazoo remote/active caps can't be as good or as quiet as the same company's best all-of-a-piece studio mics.

It's fun trying, though... long as the wishful thinking lasts(!)

Dave  8>)

I'm not sure that is totally accurate. Why would a properly designed and built active cable be inferior to a stock mic?

[Colin Liston]

Why not just buy these?

http://cgi.ebay.com/ws/eBayISAPI.dll?ViewItem&item=330445464761

AKG – 2 mk46 cables and 2 ck1x cardioid capsules

[groovon]

I have already detailed the potential limitations of such a system in the other thread, so for a person who four days ago didn't understand the effect of cable capacitance on a condenser microphone capsule to lecture me as a "skilled amateur" is, to say the least, rather insulting 

Good for you. But no need to get your panties in a knot.

I don't know you from a bar of soap, and my comments weren't directed at you personally, anyway.

I've designed and built stuff from mic preamps to tube guitar amps for damn near 40 years. I doubt you could teach me much I don't/didn't already know about high-impedance circuits (unless I've forgotten it!)

Good luck
Dave (proud 'skilled amateur' audio tech for 40 years)

[groovon]

Why not just buy these?

http://cgi.ebay.com/ws/eBayISAPI.dll?ViewItem&item=330445464761

AKG – 2 mk46 cables and 2 ck1x cardioid capsules

Colin - $800? Too steep for me. Aren't they electrets? Powered off the 13.5V on the contact ring in the 460 preamp, I think. I'm happy enough for now with my 460s and A61 swivels. Thanks, though.

Dave

[groovon]

No, you suggested why the experiment might not work (shunt capacitance of the cable), which I was quite well aware of else I wouldn't have been restricting the cable length to a mere ONE OR TWO FEET(!) 

Cheers!

[groovon]

Yes, 'theoretically'!

There is much wishful thinking going on on this subject! "Just stick an FET in there and Bob's yer uncle!"

Right. 'Easy' to make a CK6x cap sound like a $20 Radio Shack lapel mic.

Schoeps, AKG spend millions on R & D and have reputations to consider. They don't allow anything out that will sound like crap. So maybe there's a reason why AKG C460B/ULS system mics are the way they are, without 'active (true condenser) caps'. I'm just sayin'.

The reality is, even from a skilled amateur's workbench, it will not happen without some loss of signal-to-noise ratio and degradation or change in quality. Even the high-end R&D'd-up-the-wazoo remote/active caps can't be as good or as quiet as the same company's best all-of-a-piece studio mics.

It's fun trying, though... long as the wishful thinking lasts(!)

Dave  8>)

I'm not sure that is totally accurate. Why would a properly designed and built active cable be inferior to a stock mic?

I just meant that, all other things being equal, the best performance will be with the cap and amp as close together as possible. Schoeps himself says exactly that in his patent papers, but then adds, "in the recording of sound, it is frequently necessary to keep the use of the microphone as inconspicuous as possible", thus his remote cap idea (link below). It isn't to increase audio fidelity that we want this, it's purely for convenience. Not that it isn't worthwhile to try and get the best performance you can from this setup, just that it won't be as easy as some might think.

http://www.wikipatents.com/US-Patent-4002859/multi-mode-electrostatic-microphone-construction/Page-5

(thanks to mshilarious, I believe, for the link.)

Cheers
Dave

[groovon]

You're still telling me what I more or less already knew, and insisting I didn't know it. One can know things in theory, and still wonder what would happen in practice, perhaps bending the rules. Or maybe you're above that. The experiment was casual at best - RG-58 was what I had on hand, and another type of cable wouldn't have made the experiment 'successful'.

Please don't insult me, I'm well aware of the theory and importance of impedance matching, and have been since I was about 16 years old. This particular case is an extreme one though, and quite possibly you have more experience with Gigohm-range circuits than I've had. There you go, happy now?

Good luck with the project

(BTW, I did not 'forecast doom and gloom' on the project, I just noted that a lot of people posting on it had too-simplistic ideas about how easy it would be to accomplish.)

Dave