Studio / Patchbay grounding methods - help needed

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mig27

Well-known member
Joined
Jun 10, 2004
Messages
118
Location
Berlin
hi folks,

I'm about to reorganize my patchbay since I can't seem to get rid of various hum problems.

here's what my set-up looks like:
  • studer 189 mk II console
    => transformer balanced, constant 48V phantom on the inputs
    the console has a massive ground lug on the rear, not used right now

    various electronically and transformer balanced 19" units in the rack

    various unbalanced rack units (mostly FX boxes)

    various transformer balanced telefunken modules that are not integrated to the 19" rack

I'm planning on using separate parts of the patchbay for balanced and unbalanced gear respectively.
Also I'll take a heavy gauge wire and link the console's ground lug to the metal frames of my racks and common chassis of the telefunken modules.

Is there anything else I may need to take into account?
Any insight on general trouble shooting for hum problems?

thanks heaps.


michael
 
Michael,

There's a lot to take into account here- let me take a shot at it when I've got more time!!

Have a read of some of these to help for now:

From Rane website:

Rane sound sys interconn. Note 110:

http://www.rane.com/note110.html

http://www.rane.com/pdf/note110.pdf


considerations in gnding and shlding audio devices

http://www.rane.com/note151.html

http://www.rane.com/pdf/note151.pdf


system problems and equip manuf.

http://www.rane.com/pdf/whitlock.pdf


grounding and shielding with computers

http://www.rane.com/pdf/compgrou.pdf




From Jensen website:


Interconn bal and unbal AN003

http://www.jensen-transformers.com/an/an003.pdf


Hum and buzz in unbal interconns an004

http://www.jensen-transformers.com/an/an004.pdf


AS032 Build the Hummer to find Pin 1 Problems

http://www.jensen-transformers.com/as/as032.pdf


AS085 Proper grounding inside equipment

http://www.jensen-transformers.com/as/as085.pdf

It can be very complicated getting a patchbay working in a balanced/unbalanced environment. The first thing to do is to work out how many points you need, and then add a bunch more (you won't regret it!) And allow more cable than you think you'll need. And more patch cords. Then draw out the actual physical layout- where you want the console inputs, inserts, buss outs buss inserts, outboard, recorders etc. I'm not sure I'd be happy bringing "always on" phantom to a patchbay either, unless it was an XLR bay. Accidents can happen.

The main problem with unbalanced equipment is the level problems- most gear runs at the lower -10dBv rather than +4dBm, which means a level difference of nearly 12dB. This means overdrive and clipping going bal>unbal, and noise and low levels going unbal>bal. If you really want a trouble free life, I'd build some active balanced>unbalanced and unbal>balanced converters and hardwire or patch it into the unbalanced gear.

It sounds like the majority of your gear is balanced, and I like to keep a studio as balanced as I can (especially in this age of external noise :roll: ) and then balance any unbal gear. But that's just my experience. I know sismofyt and Jaakko have both gone the unbalanced route. But having everything balanced means that you can hire in other pro gear and guarantee a working studio.

Anyway, here's a start- I've said more than I was going to say- I could talk balanced/unbalanced/patchbays/grounding/tie-lines all day...but I've got stuff to do!!

:guinness:

Mark
 
wow i've been reading that and it very informative, thanks!

however, this brings up a question i have been pondering.. how to *properly* hook up mixer inserts through an unbalanced(balanced?) patchbay to various (un)balanced equipment.

right now, my inserts go to the patchbay so that the top rows of each box are sends(from mixer) and the bottom rows are the returns(to mixer) so that i can chain them if needed.. now this seems to work fine for me with no real problems. my noise floor rides around -75db( all faders/trims @unity) which i know isn't the greatest but is not humming or picking up strange noise(other than normal white static).
 
My gear is an unbalanced / balanced mixture, and I have no hum or trouble with my patchbay, so I just tell you how I've done the cabeling:

all balanced I/Os are conected balanced (2:2, 3:3, 1:1)
all unbalanced Inputs are connected tip:2, ring:3&1
all unbalanced Outputs are conected tip:2, ring:3&1, 1 left open at the patchbay

may be not everyone will like this, but it works well ...
never had any hum problems with this, neither at work nor at home

try it :grin:
 
I'm riding my rack unbalanced as well and have a very low noisefloor (like 80-85dB from the synths thru effect thru mixer thru mastering effects thru a "mixermixer" thru master limiter to AD) maintaining "pro"-level from the first mixer on.
After reading the jensen article about balancing solutions i'm searching for free space in cases...
(my "pimped up" cheap 1993 and 1994 spl vitalizers even have an upgradeable pcb / no docs required...definately worth a step to balancing my mastering section...)
Very informative and easy to understand...nearly "simple".

thanks alot for the links. essential.
 
best read concerning this subject is Philip Giddings: Audio Systems Design and Installation. More than 500 pages about power, grounding, interconnection, cables, connectors, wiring and housing. This book is worth every cent.
:guinness:
Jens
 
Yes,

Scenaria mentioned this book on TT, so I picked up a copy and has been a constant source of reference (and bedtime reading :shock: )

:thumb:

Mark
 
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