Patchbay Normaling Question

[Siegfried Meier]

Hey guys,

I've been wiring up a few TT solder bays the last few days and had a quick question.  We've got snake lines on the bay half-normaled to the mic preamp inputs, and a buss bar is connecting all the grounds together for all of those.

Now, I'm wiring the mic preamp outputs to the inputs of the Digi converters, also half normaled, but I'm not sure if the grounds should be joined in a similar manner, or if each top TT connector (Mic Pre output) should just be grounded to each bottom (Pro Tools Input) via the normal cable.

http://www.caneaudiosystems.com/TL_theassemplyPT_2.html

I've used punchblock style in my studio, and I can't recall if the grounds are internally connected on those, which is quite common on some of those ADC's.

Any info much appreciated.
Thanks!
Sig

 

[pucho812]

the tie line snakes to mic pre inputs should have a full normal not a half normal. I would change that.


Now as far as bussing grounds I have yet to see any console manufacture do anything else other then bussing grounds, bussing the grounds at the patchbay allows the patchbay to be nominated as a central point in a star grounding system. In other words the wa your other patchbay is wired with a buss bar connecting all the grounds together is a good way to go.

 

[JohnRoberts]

I dislike patch bays... momentary shorts on phantom powered mic inputs can put 50V spikes on mic inputs.

Optimal treatment of grounds shouldn't be that difficult for properly engineered balanced/differential wiring. In the real world with legacy gear, YMMV.

If you determine that you have some oddball gear that needs special ground treatment, it may be possible to add a few patch points with ground lifts or whatever that you can path in series for different treatment.

Or not...

JR

 

[Siegfried Meier]

Most studios I've worked in are bridge out/break in for snake panel/mic pre ins.  Plus the fact that you can mult snake outs to multiple preamps for either comparison or a different style of processing.  But I think I know where you're coming from here - if phantom is on, then that will hit the snake line as well as it travelling to whatever other preamp you plug that into.

As far as the shorts, yes those can happen.  The buss bar is supposed to alleviate this issue BUT, you still gotta pay attention and normalize the gear at the end of a session (biggest thing being turning off +48v).  Goes with the territory of engineering, I think.

Regarding the bussing - I will buss bar all the preamp outs to PT inputs then, yes?  Thanks dudes!

 

[jplebre]

most patchbays will short the ground anyway through the front chassis.
Our G4000 only has 1 ground wire connected, nothing else - because the front panel is conductive.

You should change your mic line -> preamp input section to fully normalled. This is actually easier to do as you connect the hook-up wire for the normalling on the normal pad.

 

[Siegfried Meier]

I know what you're saying...but I won't be changing it now haha.  I actually prefer it this way, and so does the client.  I was speaking with Bob (aka Mr. Patchbay) and he also gave me some good info on why half-normal is better in many situations.  You must just exercise caution, that's all.

Thanks guys!
Sig

 

[joaquins]

From mic I'd go with the full 3 connection wire to the preamp, no other place connected the ground.
Everithing else balanced line output or input wire ground connection only to the patchbay buss bar, the other end ground not connected, chassis/ground of all other equipments connected to a nice star point in the room. This way you don't have current on the cable sheild and your safety ground is solid, If something is unbalanced then you need this ground to get the signal in, you can use here the other signal wire as ground signal and the shield as any other, so in the patchbay you have sleve to shield, ring to ground of the other end (the unbal equipment) and tip as the hot signal.

JS

 

[pucho812]

I know what you're saying...but I won't be changing it now haha.  I actually prefer it this way, and so does the client.  I was speaking with Bob (aka Mr. Patchbay) and he also gave me some good info on why half-normal is better in many situations.  You must just exercise caution, that's all.

Thanks guys!
Sig

typical normal connections are usually full normal between mic panel and mic pre then they rest of the patchbays(line in's, busses, inserts, etx) are half normal. The outboard gear is usually wired with no normal aka open. Outside of that there maybe one or to stray full normals, half normals and open depending on a consoles master section.


I do not understand the need to have a half normal on the mic panel to mic pre input as an attempt to split mic signals. That kind of action is best done with transformers.

 

[Dreams]

I was under the impression that a Y-cable type splitter on a mic was a no-no. Do people audition mic pres this way? Won't that just mess with impedance/loading/etc and make it sound different anyway?

In what situations would a half-normaled mic patch point be preferred?

 

[jplebre]

Do people audition mic pres this way?

no

Won't that just mess with impedance/loading/etc and make it sound different anyway?

it willl

In what situations would a half-normaled mic patch point be preferred?

when you have no other choice, or - never

it may lead to other problems - eg. adjusting one pre changing the level/tone in the other, etc.

Also, I'm not quite sure what will happen if you feed +48 from 2 channels.
Most large format pro desks, specially the ones from the 80's till early 2000 will most likely not have phantom power LED. The VR case comes to mind where the mic pre gain is pushed in for ON and is barely visible

 

[pucho812]

ON the VR desk, the pot also has a switch that is push pull action. Pushing down engages the switch which turns phantom power on. The console silk screen reads pull up for PH off but most noobs stop reading after PH so they will pull up and turn phantom on.. They often do not 100% normal the console so often times the phantom is left on.

 

[jplebre]

exactly my point

They often do not 100% normal the console so often times the phantom is left on.

and good bye your very expensive vintage ribbon

 

[pucho812]

exactly my point

They often do not 100% normal the console so often times the phantom is left on.

and good bye your very expensive vintage ribbon

I just realized I should have used zero out instead of normal as to not confuse the young ones.

As for ribbon  mics and phntom although not a good practice you can have phantom on a ribbon and all will be o.k. as under regular conditions of plugging in an XLR it gets equal tension on both sides of the ribbon motor and no damage occurs.  So what damages a ribbon in relation to adding phantom power? It's when you cross patch on a patchbay tt, 1/4, or b-gauge the mic lines with phantom on as you short one side to ground as your plugging in on the patchbay.

watch this video
http://www.youtube.com/watch?v=YmHgPbSqhAE

 

[mikeyB]

I dislike patch bays... momentary shorts on phantom powered mic inputs can put 50V spikes on mic inputs.

Optimal treatment of grounds shouldn't be that difficult for properly engineered balanced/differential wiring. In the real world with legacy gear, YMMV.

If you determine that you have some oddball gear that needs special ground treatment, it may be possible to add a few patch points with ground lifts or whatever that you can path in series for different treatment.

Or not...

JR

exactly my point

They often do not 100% normal the console so often times the phantom is left on.

and good bye your very expensive vintage ribbon

exactly my point +BIG 1!

I used to maintain a big console in a teaching establishment and boy - did i maintain it regularly!!
Patcbay was full normalled but the studio tied to numerous live rooms.
I'd spend a good few hours lifting each channel and replacing protection zeners on the desks mic inputs (or replacing tweeters!!)
It got a bit disheartening watching the students start to swap the patch leads with phantom power applied - felt like whipping them with the patchleads! - wouldn't have thought twice about it had it been my private studio!!!
But if it's a must - then make it fully normalled - i've seen some desks "take off" and oscillate where 2 mic pres are tied together on a semi normalled patchbay.

 

[jplebre]

But if it's a must - then make it fully normalled - i've seen some desks "take off" and oscillate where 2 mic pres are tied together on a semi normalled patchbay.

Yes!
And why didn't you beat those students? I think I have for way less.

In fact, pull a VR module out and chase them out of campus. I'm sure they will not forget to turn phantom off before patching anything next time