Microphone level patchbays earth question

[Paul Maybury]

Hi, I am about to install patch bays for my mic feeds and pre amp inputs so that I can have three rooms instead of one connected to my control room.
I have purchased TRS patchbays for this job. I am aware of the issues of having phantom on while patching, and fingers crossed nobody does anything stupid...Of course, eventually they will. But that's not the question.
How should I run the ground in these TRS bays? Should I ground everything together back to the console chassis, or only have grounds connected per channel? Should I avoid any normalling?
Everything else connected to the control room has ground connected only at the console end.

Anyone?
Cheers,
Paul Maybury

[Hookemeister]

Hi Paul, thought I might chime in as it doesn't look like anyone's offering you any advice.

I'd stay away from patchbays for low level signals such as mics. My advice would be to bring the mic feeds from the 3 rooms into the control room and terminate them on a Male XLR patch panels and the console mic inputs on a Female XLR patch panel. You can get pre-punched 1RU XLR panels that will take 16 Neutric XLRs. Wire up some short male to female XLR patch cables and your ready to go..

If you insist on using a TRS patchbay I'd highly recommend that you do not run the mic signal via the normaling springs, that's just asking for trouble.

Running +4 thru a patchbay that goes high resistance or one leg goes open circuit will give you a bit of static and hum, but the same situation with a ribbon mic into a preamp with 60db of gain... that static will take out your monitors... those precious 604's!

I've had a lot of experience with TRS patchbays from telecommunications thru to broadcast and I can tell you they need to be used. If lines are left permanently patched for any extended period of time then there's a good chance of the the earth connection, via the sleeve of the plug to the barrel of the bay, going HR.

As to the grounding issue, the patchbays are no different to running another mic extension cable. Everything is grounded from the console back to the mic.

Usual rules apply: Good quality, low capacitance cable, good quality connectors and excellent soldering skills.

Preventative maintenance: Regular cleaning of patchbays and patch cables. Regularly check mic cables with a multimeter for low ohms continuity.

Hope this helps.

Greg

[Paul Maybury]

Thanks a lot Greg. I would rather use XLR panels, however, space is an issue as I will be bringing in three rooms on the patchbay, 24 channels each.
I'm quite nervous about this.
Any other suggestions out there about how to run a multi room facility without the mic level patchbay woes?
Cheers,
Paul

[Hookemeister]

Male Mini XLR Chassis Mount. Like they use on lavalier mic transmitter packs.

You'll get 24 of those on a 1RU frame.

[Paul Maybury]

Thanks Greg, never thought of that!
Paul

[dave01.cooper]

Hey Paul,

Slightly relevant but take a look at a thread I put up a while ago about some bantam bays I revived and integrated into our system.

viewtopic.php?f=5&t=8586

Basically bay 1:
top = 24 ties from main live room, 4 ties from kitchen, 4 ties from iso.
bottom = soundtracs mic ins (24 live room ties normal to these). The other 4 & 4 are isolated.

I've never had problems patching these into my external pre's via bantam bays. There is noise but it sounds like any other microphone noise floor, nothing exaggerated. I understand the reasoning for using XLR patchbays for mic -> pre patching but space wise just wouldn't fit with our setup unfortunately...


Anywhom, food for thought.

[Paul Maybury]

Thanks Dave. I have had a rethink about all of this and I'm going with XLR patchbays. I'm sure TRS or bantam can be fine, but finding these was the clincher,

http://artproaudio.com/art_products/aud ... oduct/p16/
as I need to have 96 patch points for mic level stuff, space is a factor and these ART bays are 16 way so that adds up compared to all the other xlr bays I've seen which are 12 way.

They make it very simple and not too costly to set up a completely separate xlr bay.
That said, I now have a whole lot of xlr-trs looms and a couple of 48 point trs patchbays that I will never use....
Cheers,
Paul

[Hookemeister]

Hi Paul,

A word of warning.

Be carefull with with any kind of connector that direct solders to a PCB.

Over the years I've seen many intermittent faults in jack sockets, RCA's and TT jacks that connect directly to a PCB.

Constant movement from plugs being inserted and removed cause hairline solder cracks where the terminal is soldered to the PCB pad.

If the XLR pins are mouded into the casing and firmly supported by the casing of the XLR then it shouldn't be a problem.

Open up one of those ART bays and check the quality of the connectors and the soldering to the PCB before you purchase a stack of them.

If it were me, I'd be getting a prepunched 16 XLR frame with a lacing bar, load it up with Neutric chassis mount XLR's and solder the cable directly to the pins.

Hope this helps.

[Paul Maybury]

Hi Greg, thanks for your insight. The ART's appear to have the connectors screwed to the panels, so hopefully they don't fail for a good while.
Unfortunately I don't have time anymore for big soldering jobs like a 96 point patchbay, these ART's look like the best and most cost effective plug and play solution. Hope they don't bite me in the arse down the track sometime. Of course they are sure to wear out eventually.
In any case, it's gotta be better than a TRS or TT solution.
Cheers, Paul

[dave01.cooper]

16 ch per 1RU frame, nice. That's better than the 12 usual that's for sure!

On another note - mini XLR is a bloody good idea... Any idea if you can get panel mount mini XLR male & female connectors? And if so, where from?

Cheers

[Hookemeister]

Unfortunately I don't have time anymore for big soldering jobs like a 96 point patchbay

Won't you have to wire & solder 96 XLR plugs onto the tails of multicores coming from each room???

If the answer is yes, then it would be a lot quicker to wire the back of chassis mount XLR's than XLR line plugs.

Anyhow here's some info if you need it or for anybody else looking in that area.

http://cdn.madisontech.com.au/pdfs/Madison_BAV_Catalogue_Vr3_for_email.pdf

Download the catalogue and go to Page 28.

XLR Patch Panels - Madison Broadcast AV Catalogue.JPG

Hope this helps.

[Paul Maybury]

Hi Greg, I am using xlr multicores with stage boxes to run mic lines and cue returns. All wired and ready to go. So the tails just plug into the backs of the ART bays and I patch at the front. The stage boxes can be wall mounted in the live rooms.
It's not very "pro" of me, but I am quite happy to not have to solder all of that....
This way also allows me to very easily re use or even re purpose the cabling and patchbays if I have to move my studio (touch wood this doesn't happen for a loooong time). If it was hard wired, it would be much more difficult.
Cheers,
Paul

[Hookemeister]

Any idea if you can get panel mount mini XLR male & female connectors? And if so, where from?

Hi Dave, yes you can... but unfortunately the male comes in the form of a nut & and washer affair and the female is more akin to a standard panel mount XLR... see below.

Mini XLR Male -Chassis Mount Size.JPG

Mini XLR Female -Chassis Mount Sizes.jpg

You can easily fit 24 across a 1RU frame.

Where do get 'em? Anywhere from eBay thu to Farnrel/RS Components, depending on quality and price.

Try Wagner Electronics.

Hope this helps.

[Hookemeister]

This way also allows me to very easily re use or even re purpose the cabling and patchbays if I have to move my studio (touch wood this doesn't happen for a loooong time). If it was hard wired, it would be much more difficult.

Good thinking 99.

Plug & Play... I like it. Less time to plug & more time to play.

Cheers