mics to a patchbay - best way?

[lilcapn]

i'm on the verge of entering patchbay world, and i'm trying to figure out the best routing for what i've got (VS-1680, soundcraft spirit board, soon a TSR-8 tape machine, a few pre's and minimal outboard gear -- RNC, Space Echo, Effectron, etc).

the situation that i've gotten mixed advice on is, how to run the Mics themselves into this situation so that i have the flexibility to use either the board pres or other mic pres in the Rack.

-- an XLR-1/4"tsr snake to the back of a balanced patchbay, normalled to the board, so that i could break the normal by patching in a mic pre seems logical to me, but i've read that this could create problems in regards to phantom power that's being applied, etc.

-- an XLR patchbay? are these common?

thanks for any advice!

mac

 

[skippy]

Well, I'm one of those folks who believes that you really don't want to put phantom power through a TRS patchbay. My claim is that you don't even want to put mic level signals through a TRS patchbay at all, if you can avoid it.

There was a long thread on this topic going over in the "Studio Building and Display" forum some time back, and I posted some photos of my rig over there. The pointer is https://homerecording.com/bbs/showthread.php?threadid=25365&pagenumber=1

The bottom line for me is "they don't go there": my TRS patchbay is all line-level-signals only. All the mic patching I handle separately on an XLR bay.

TRS jacks momentarily short tip, ring, and sleeve as they are disconnected. That makes for an easy way to blow up both mics (NEVER hotpatch a ribbon mic...) and phantom supplies, not to mention the damage to the monitors if the gain is up when you hotpatch: the resulting 48v-fullscale-pop can and will put your cones in orbit. Hotpatching mics is a crime against nature, but in the heat of the moment, it's going to happen. With XLR hotpatching, at least ground is the first signal to be connected and the last to be disconnected, which means you don't run a 48v square wave into your mic preamp.

One other issue: It also ain't much fun to mistakenly patch a mic input with +48v phantom onto an unsuspecting line input with raw opamp inputs powered by say, +-15v. The input protection diodes go, and you just killed that input... Not good. So I eliminate that hazard by not *allowing* it to happen, except in very limited extreme situations.

This doesn't mean that you absolutely should never run mic lines through TRS bays: I do it when I have to, and so do most professional rooms. However, you should probably work really hard to avoid doing it as part of a normal day's recording.

I built a separate strip with XLRs to do the small amount of mic patching I need to do: most mic positions are hardpatched directly to mic ins on the board, since I almost always use my room in one specific configuration. There's a picture of my little mic/access strip late in that thread. Anyway, I ran cables from several loose mic inputs to the XLR strip, so that I can then just plug an XLR mic cable directly into the front of the rack on an as- needed basis.

There are several companies that sell rack panels prepunched for XLRs (for example: http://www.markertek.com/MTStore/product.CFM?BaseItem=SFXLP-1 ), or with a drill press you can make your own quite quickly. The thing you give up with an XLR panel is normalling: in order to make that work, you have to put in a cable from here to there. But for mic use, I find that extensive normalling really isn't that useful. Mic assignment is pretty fluid in most setups...

Your mileage may vary, of course. Hope that helps!

 

[h kuhn]

I have had my mp20 blown by some guy hotpatching it, just because of connecting a condenser mic that draws a lot of current with the phantom set. Never ever patch it through a trs patch bay.
If you are totally religious about switching off phantom before connecting or disconnecting a mic you might not run into problems, though.

 

[lilcapn]

thanks skippy

thanks for all the info -- i had actually read those earlier posts as well -- lots of great info there, more than my brain can handle actually!

but everyone seems to have a point about not risking blowing shit up with the 48V, so having the mics going into an XLR patchbay and into the board seems like a good idea.

what i'm still having trouble envisioning (and maybe this is because i'm picturing the XLR patchbay incorrectly) is how i'd then insert an outboard mic pre into the chain if i didn't want to use the pre on the board...you wouldn't have a mic pre patched into a regular patchbay and use it as an "insert" would you? i don't even know if that would work, seems kinda backwards.

thanks!
mac

 

[skippy]

If you use external pres, consider doing it this way:

1. Set up your XLR patch bay to have one female XLR per preamp input. Wire from the back of that to a male XLR to lug into the pre itself.

2. Set up a *separate* 1/4" TRS bay to have 1 jack per preamp output. From there, you can then patch the pre's output to the jack that connects to a line input, or an effect input, or whatnot.

You can really think of an external mic preamp as an XLR-to-TRS converter with gain, in that case (;-). I very much like doing things this way: if it's on a TRS jack, it's line level. If it's on an XLR, it's mic level. Makes it easy to keep straight...

I've seen some folks make a mic pre patch panel with the female XLR for the input right next to (or above) the TRS jack for the output. Tidy, and easy to get a mental picture of the signal flow in a complex setup...

And yes, in fact a lot of people do use external preamps and EQ, and inject the result into their boards *through the insert return* (after converting from balanced TRS to single-ended TS, of course). This completely bypasses all the internal electronics in the channel on the board, and simply stuffs the external signal directly into the fader, channel route switching matrix, and summing amps.

For boards with noisy preamps and/or nasty EQ design (but decent summing amps!), theis technique can extend the usability quite a long ways... This lets you take some fairly cheap and nasty boards, and still get remarkably good results- by simply chopping a lot of the board's electronics out of the path. This is one good application for those all-in-one "channel strip" products: they do all the work, and the board truly "just mixes" at that point...

If you are doing seriously high-quality recording work, getting as many stages of electronics out of your signal path as you possibly can is a _very_ good technique. So you'd really prefer not to use an external channel strip, and then run the signal through the board's preamp and eq, even if they are set for unity gain and no boost or cut...