Wiring Your Studio with Audio Over Cat5 (AES72/QTP/RJ45)

[aidanknight]

Only if you remove the 48V at source. Or you could fit some isolating capacitors. However, ribbon mics are perfectly safe on phantom power...IF you had a really old mic worth a 5 figure sum you might avoid spook juice but even designs as old as the Coles (orig STC) 4038 are regularly connected to phantom lines at the BBC, millyons of times, for years!

I will draw you something up the morrow.

Dave.

I've seen too many ribbons blown up when someone starts patchbay swapping with +48v running. Happened to an RCA 77 on a session I was playing on. The control room got real quiet and the house engineer walked over the assistant and asked to "see him outside for a moment". They never returned.

 

[ecc83]

I've seen too many ribbons blown up when someone starts patchbay swapping with +48v running. Happened to an RCA 77 on a session I was playing on. The control room got real quiet and the house engineer walked over the assistant and asked to "see him outside for a moment". They never returned.

I don't say it could not happen and the RCA77 is a near $3000 microphone of exactly the type I said you should be careful of. Yours is the first actual report I have read of a ribbon being damaged and I have never seen a documented case with a post mortem of the mic showing the damage.

I also do not condone the presence of phantom power on a TRS patch bay. Not only can ribbons be damaged but the 'sequential' connection of the plugs leads to pops and bangs in the system with potential damage to speakers. Ears don't like it either! The presence of 48V on a TRS jack is an accident waiting to happen, for sure someone will plug in a device that is not protected and that means most things.

Keep mic circuits on XLRs and all others on TRS and the risks are minimal. Even better, have some mic outlets with internal 47uF caps in them.

Dave.

 

[rob aylestone]

I too have never seen a microphone die from accidental application of phantom - even though a jack is a terrible connector for phantom as the plug makes contact with the three wipers sequentially, not at the same time as in an XLR, and even XLRs can be wiggled on insertion so 2 and 3 make contact at different times. However - you can see a ribbon twitch when it's plugged in with phantom applied, or the phantom is switched on. There is a teeny movement. I've never seen it kill a mic. I thought I'd done it to an STC commentators mic that I bought second hand. I plugged it in, with phantom on and the level up and got the usual unpleasant crack. The mic sounded thin and weedy, and I figured I'd ruined it, and never used it. I bought only last year, a new one for a project and discovered the sound is exactly the same - thin and weedy and only gets the well known characteristic sound when the commentator ups the voice and gets excited. I hadn't damaged the other at all.