Tt-phone patchbay and 48V phantom power

[g-slam]

Hi,

right now I am soldering 3 Bantam patchbays.

First one is connected to the recording rooms wallbox. The Outs are normalized and go to the inputs of my Metric Halo interfaces which have MIC Preamps included.

The second patchbay is for the Metric Halo Outputs, going to a summing amp.

The 3rd patchbay is connected to my outboard gear, so I can switch a Mic to an outboard preamp and go back to the DAW-Interface, or I can insert a compressor for mixing.

My question:

If 48V is powered and i change the Mic to another preamp, is the 48v short circuited?
How can I prevent this?

JOnathan

[Aaronw]

Hi Jonathan,

I must have missed this post.

Phantom can be run through a patchbay, but you want to be aware of what you're plugging in when you do.

Example would be, maybe plug / unplug your microphones before patching, etc. Also, don't accidently run a patchcord into the wrong insert to an outboard piece of equipment, etc. (you'll fry an input or output possibly).

Several consoles over the years, have that normalled in their patchbays w/ phantom running through them. Also, if the mic pre has a phantom switch, you can turn it off before patching.

[EK Sound]

I personally never use anything but XLR for mic patch. Yes, it takes more rack realestate, but the patch is rock solid and there is no mistaking which patch is which. One studio I worked at had bantam bays for mic patch built into one wing of the console. Every time we cranked up the mains, we would get these little crackles in the audio. We finally traced the problem to the bay vibrating (Urie 813C mains). It became common practice to put a roll of 2" tape over the cables to weigh them down so they didn't move.

Dave.

[franktree]

Sorry to revive an old thread, but I'm new here and trying to get my head around this particular question. I would like to have the ability to have the preamp inputs to my console, and inputs to various outboard preamps come into a patchbay alongside mic signal outputs from my wall box, so that I can easily patch any output from the wall box to any preamp without needing to rewire.

Is the idea here that I need to use XLR patch panels for both the console preamp inputs and external preamp inputs, and then I just need to manually connect the mic tie line outputs to these XLR patch panel inputs to avoid this phantom power issue? There's no way to run it via a patchbay so I can just patch, for instance, Mic Line 4 into console channel 10, and then quick change so Mic Line 4 is now running into external preamp 2, without needing to plug and unplug XLR cables?

[DanDan]

Patchbays are trouble. Go XLR.

[franktree]

What does going XLR entail exactly? Having XLR patch panels that go to the console and outboard preamps, and then needing to plug into each manually each time you want to plug a mic in? Is there any better/more efficient way to do it?

[gullfo]

using an XLR panel to connect (especially phantom power) mics is generally a safer bet than a normal patch panel where mistakes with phantom power can lead to heartbreak... so you would have a row or two of XLR connects which have terminations for the snakes and pre-amps. then short XLR patches to connect. you could also use neutrik connectors which have both XLR and 1/4" TRS and keep phantom power connections to the XLR pins, and leverage the TRS for non-power IO. this preserves the rack panel space and routing options open.

[owenj7920]

Hi there, dilemma here - some people avoid and or say it's bad to run mic signal through a patchbay as if there will be some loss of quality or something. I was initially going to run my mic lines from the live room directly to pres, but that makes it a bit of a pain to patch in a mic or a DI'd synth or whatever into the preamps from the control room via an XLR to TT.

Is there a formal conclusion on where it degrades signal? These are high-quality Switchraft 9625 patchbays btw.

If I were to have mic lines in the patch bay, I'd have them normally or half-normalled to the pres.

Yes, specifically it's like this:

The shield/ground that runs between a single microphone and its pre-amp is one of the most critical interfaces in the whole studio, and it must be isolated from other microphone shields/grounds. I also wants it to attach automated payroll software, but I am unable to do that properly. If the patch bay in question is "buss-grounded", or does not keep each microphone shield isolated until it hits preamp circuitry, then that invites problems.

Usually, when you do happen to see TT mic patching, it is a specially designed or modified bay to keep the mic grounds isolated from patch-bay chassis, and from each other, etc.

I use an MCI console that does have built-in TT mic patching, but that part of the bay is isolated. Also, mishaps DO happen occasionally with TT mic patching and phantom. Engineers have blown ribbon mics in my studio by not handling the TT patching with extreme care, but we also have switchable phantom.

[gullfo]

at any point in the analog signal chain (and perhaps sometimes in the digital paths) your interconnections can cause issues with the signal, as well as mixing different possible ground (and badly - chassis grounds) levels. and as you noted people make mistakes through TT and TRS patches with phantom power. one way to remind people to do it is to have sprint loaded caps which require someone to move it in order to patch - hopefully reminding them to turn off phantom power. or having separate power for mics.
however, investing in good quality connectors will help with retaining signal quality as will minimizing the # of interconnects. so use soldered lines from the XLR patch (for example) to the preamps XLR inputs. removing 1 interconnect.