Topic: What are "active" cables? What good are they?

[evilchris]

I've seen this around here for a while, and even googled a bit, but I'm still bewildered.

thx in advance.

[stevetoney]

Elaborating a little bit...by separating the capsule from the mic body, it allows a smaller package at the receiving end.  For example, a mic capsule can be clipped to someone's lapel and make for an unobtrusive package.  For us in the taper world, they're used largely as a convenience and to add flexibility in recording setup options.  For example, you have the option of running with the microphone body attached directly to the capsule or put the active cable between the body and the capsule and run the capsules remotely from the body.  Whether one considers this added flexibility to be 'worth it' is a subjective thing.

Technically, the term 'active cables' can be somewhat misleading.  In our world, we generally use that term to refer to ANY cables that are used to allow mic capsules to be run remotely from the pre-amp body.  However, there are a couple of different types of cables.  First is a set of cables that has electronics integrated with the cables.  In that case, at either end of the cables there are some permanently installed modules...their purpose is to boost and condition the signal between the mic capsule and the pre-amp body.  In other setups (like MBHO 603a) that circuitry is integrated with the mic capsule, so the cables are literally just cables with mini-XLR connectors and there's nothing special about them.   

Hope this answers your question.

[morst]

In other setups (like MBHO 603a) that circuitry is integrated with the mic capsule, so the cables are literally just cables with mini-XLR connectors and there's nothing special about them.

Neumann's KM100 system has cables like this. If I wanted to be precise, I would call them something like "balanced cables for remote capsule operation"

I didn't realize that some cables actually contained active (powered) electronics! Y'learn new stuff round these here parts all the time!!?!

+t for the info, guys!

[Nick's Picks]

no, the neumann cables are active.  they have circuitry in the ends (both ends) on the non-lemo version

[DSatz]

We had a full discussion of this topic just a few months ago. See http://taperssection.com/index.php/topic,93937.html .

Let me point out, though, that Neumann's extension cables for the KM 100 series are neither active nor balanced. The first stage of the microphone's circuitry (the FET plus biasing resistors) is contained in the "active capsule" while the cable simply has one lead for the unbalanced audio signal, one for the FET's operating current, and one to carry the 60 Volt output of the DC converter in the KM 100 body to polarize the capsule.

All Neumann "active capsules" consist of two separable parts: a short barrel piece containing the FET circuit--the same replaceable subunit is used for all capsules of this series--plus the capsule itself. See the attached photo.

(In fairness to Neumann: Schoeps' active cables aren't balanced, either.)

--best regards

[morst]

Let me point out, though, that Neumann's extension cables for the KM 100 series are neither active nor balanced. The first stage of the microphone's circuitry (the FET plus biasing resistors) is contained in the "active capsule" while the cable simply has one lead for the unbalanced audio signal, one for the FET's operating current, and one to carry the 60 Volt output of the DC converter in the KM 100 body to polarize the capsule.

Awesome to know that! The other thread was helpful too. I guess the LC3 is short enough that there is not much signal loss from the unbalanced remote operation. I had no idea that the three conductors were unbalanced signal and power! I actually find that pretty funny!

Just goes to show that one need not understand the function of gear to operate it effectively. Like cars. If I had to understand how a car worked to drive it, I would probably have to go back to school, or just ride a bike! (I think I understand most of how my bike works!!?!)

[DSatz]

morst, the fact is that when this technology was developed in the 1970s, it was before the great proliferation of consumer devices operating in the GHz range. Nowadays in any venue where you or I record, there is likely to be quite a number UHF transmitters near our microphones. This was not the case back in the 70s.

(As I've mentioned in another thread, I'm currently listening to the complete set of sessions from this past October's Audio Engineering Society convention--and at least a dozen of these recordings contain perfectly audible pickup of Blackberry signals. A random instance that I just came across is attached.)

The upshot is that in situations with severe electromagnetic interference, it is indeed best to have balanced signal sources--and above all, balanced inputs in the devices to which those sources are connected. That is simply a better arrangement technically.

Best of all is when the connections from the cable shield to the chassis of the equipment on both ends is absolutely as short and direct as possible--unfortunately in low-cost portable equipment, this last point is often overlooked, making the equipment far more vulnerable to interference than it would otherwise need to be. Sorry to say, much "conventional wisdom" about shielding and grounding is seriously outdated by now or in some cases, was never right to begin with.

--best regards