i'll have those mics w/swivels come mid month. then we'll move forward
Are you looking at building cables, or are you trying to immitate the schoeps ortf bar?
I think the ortf bar would be a much better option than building passive cables of a very short length. It wouldn't be too hard to mount the electronics from the inside of the 480s inside a tube, then wire the xlrs from the bodies to a 5 pin xlr socket.
As far as making active cables, does the buffer circuit function to keep the bias accross the cap at a constant value? and how do the other brands of active cables power this circuit?, do they pull power from the signal? every analog circuit we ever talked about in school had an external power supply.
The "active" cables have a FET (field effect transistor) in the collette, right behind the capsule. This is necessary to buffer the *very* low current signal from the mic element. You may get a few feet without the FET, but it is then highly dependent of the extension cable.
So, the proper circuit will have a FET very close to the capsule. You will need two additional signals: a low voltage (eg., 5-10V) source to power the FET, and a high voltage (eg., 50-60V) to polarize the capsule. The polarization voltage is high, but very low current (theoretically zero current in fact). So you can make this out of a bunch of alkaline batteries in series. A voltage invertor could be used (that is what is in the 480 body), but is more complex and IMO not needed, at least in the first version.
I've built these circuits on my workbench (look for photos in the previous Actives thread), but have not yet built a prototype. The reason is a *mechanical* one. I need "collettes" to screw the capsules into, to connect to the center pin reliably, and to shield the small circuit (a FET and a few resistors).
My offer is the following: if someone is willing to send me (to keep!) a set of machined collettes, or a set of swivels, or anything else that will solve the mechanical problems, I will build a prototype and disclose all information I discover and allow anyone to copy/build/sell the design to others. If I succeed, I will keep the system. If I fail, I will return the parts to the donor. I have already bought the capsules (a pair of CK63) and they are sitting idle on my bench, so I have contributed enough money, I don't want to buy more parts.
In the meantime, I have since decided to buy a set of Beyerdynamic actives (see the Team Beyer thread), but I am still willing to contribute to this project *in exchange for gear*. If anyone wants to step up and donate their parts, the project will move forward. I am also happy to help anyone else who actually builds something on their own.
No offense to others, but we don't need any more questions about this topic. We need someone to either donate parts, or to build something.
Thanks for listening folks...
Richard