Technical Earthing in a studio

is it possible we can start a discussion on technical earthing and good earthing procedures? some of the papers out there are confusing or not thorough enough. it would be nice if we could outline the main principles and give a step by step procedure for the average joe who runs a studio.

some of the discrepencies I have noticed are:
one paper said the technical earth must be bonded with the buildings AC Earth - another said the opposite.
one paper stated that the PSU earth should not be connected to the technical earth and then goes on to suggest taking the studio circuitbreaker earths to the technical earth. Is that not the same thing?
very confusing stuff

Hi,

Yes it is very confusing stuff, and you've got to keep in mind electrical safety as #1 priority, whilst ensuring a sensible audio grounding system.

I think the best book I've read on this was reccomended to me by Scenaria:

"Audio Systems- Design and Installation" by Philip Giddings (Focal Press)

To give you an idea of its scope- pages 1 to 113 is all about mains power distribution/technical earthing/earth connections :shock:

...an awesome book!

Mark

Studio AC ground run to one common point tied to earth grouding rod...

circuitbreaker ground/neutral tied to same earth grounding rod...


tech ground... such as a busbar in each rack tied to chassis ran back to a distributution bus that is tied to a tech earth grounding rod... not the AC mains rod...

I think thats what I got from the book

essentially keeping the tech ground and ac ground sepparate until they hit their own earth grounding rods

im sure someone can correct any of my interpretations....

ooh and that book rocks... worth every penny and then some!

Codes will differ from state to state if you have to get inspected.
If not, a copper rod 6 feet into the earth use to be the standard.
Now, it's gotten all weird where that is not used as much, as well as the cold water pipe. (hot water pipes tend to have more of a corrosion problem)
Thats the bulk of my miniscule grounding knowleged, but hey, I'm workin cheap!
:guinness:

down here the rods need to be 120 feet into the ground :green:

:razz:

[quote author="Mark Burnley"]Hi,

Yes it is very confusing stuff, and you've got to keep in mind electrical safety as #1 priority, whilst ensuring a sensible audio grounding system.

Mark[/quote]


Just to connect big SI antiparallel diodes in the safety ground in the
mains input.
In the standard state this diodes are closed and ground loop broken.


xvlk

[quote author="cjenrick"]Now, it's gotten all weird where that is not used as much, as well as the cold water pipe. (hot water pipes tend to have more of a corrosion problem)[/quote] My understanding was always that the hot water pipe was connected thru the hot water heater to the cold water pipe...so maybe a higher resistance connection?
The cold water pipe is always grounded as it runs thru the ground to the building.
But now...most cold water pipes are plastic!

Just some thoughts...Gonna have to get that book!!
Peace!
Charlie

headsup.. the book is a little expensive because its hardback... but it makes great reading!

I don't know about you guys, but my hot and cold water grounds are connected at the spout :roll: ... my building was built in the 20's and has been retrofitted with grounded outlets which was grounded to the kitchen. I have a home run to ground in the bathroom though without any fridge voltage on it. :roll: I want to put my "studio" on that ground. I don't have to be at commercial code...for now...thank god...

-from Winston-Salem...the only city with TWO cigarette brands named after it and with very few other cities in North America with an included hyphen in its name...

tie all AC grounds on circuits to the same busbar to the same earthing rod?
but surely there are still potential differences at different points on the mains circuit.
I am still not very clear on all this.
Is technical ground just for the chassis of the equipment? but AC ground is always connected to the chassis aswell/.

Phoenix Audio say to tie all circuit breaker grounds to the technical earth.
but then go on to say do not connect the console PSU AC ground to the tech ground.

I presume an important thing to do is bond all chassis of studio equipment together at one point.
can someone propose a checklist that might ensure rational progress
thanks all[/quote]

My understanding is that the neutral is your problem. Neutral is hung off the lug on the nearest step down transformer. I usually condition the neutral with not too expensive tripp-lite style boxes. With the neutral conditioned you are free to ground the studio system anywhere you want. There can be a difference of potential if you have a technical in addition to the building ground, but conditioning the neutral seems to keep it from being a problem. Depending on how far along you are in the building/renovation you may also want to consider balanced power. There is balanced power in the form of very expensive, lights up the neutral with 1/2 of the mains voltage and sends the other half high, dedicated boxes. These seem useless unless you are ready to commit to the expensive proposition of doing the whole studio with them, and they tend to creep out inspectors so don't even mention it to them. There is also balanced as in three phase from the pole to the building mains, quiet, much headroom, potentially more expensive than the former if you don't already have three phase service, and ground can still be a problem, but when it isn't, darn a three phase balanced system can be some kinda quiet.<%insert appropriate emoticon%>.
Power has been one of the most fun things for me, I'm looking forward to reading that book and finding out about all the things I have been doing wrong.

my studio has three breaker legs. the lights and general outlets are on one leg straight to the breaker. the console, monitors and amp are on another and the outboard gear is on the 3rd. the only grounding i have is through the breaker panel. the patchbay isn't grounded except for through the grounds in the console on a plug for plug basis. the outboard stuff is grounded through it's AC plugs, the boxes are not grounded to the rack, nor to earth directly. I know this goes against all things we have "learned" to do to keep noise at a minimum but I have never had a problem with AC hum or external noise at all. I have a -75db noise floor with all channels un muted and faders @unity with all equipment set normally. this includes both pro and semi-pro equipment, balanced and unbalanced. the noisiest thing in my audio chain is my sound card! it picks up the fans and HDDs and has a noise floor of -60db. I used to study and test rack cases for EMI emissions in an effort to get a product to pass FCC (which it did) and a lot of our problems were ground loops created from holes of various sizes in the chassis. our solution was copper tape and foam with wires in it, and later a different chassis design.

our studies never once showed problems through earth grounds(even with large racks of these things and lots of testing gear on the same racks, some audio devices, some digital devices, some RF devices all running together side by side with no problems!). I believe that the earth grounding problem is more of a power supply problem with noise coming from the devices and being distributed evenly through the gear with everything hooked together via ground straps. If we(manufacturers) built the things right to begin with there would be no need to go to great lengths to quiet them down. I'll also add that most of my boxes are toroid PS based with filtering at the AC inputs, including the ground. Throwing a band-aid on it by giving the noise a less resistive way to ground may work but it shouldn't allow us as engineers to slack off and hope that our product won't be too noisy, we should still strive to design it right and perform well even in the worst case scenario. That is well within our power and ability.

just my .02$

My system is extremely quiet and hum free - apart from my Ampex 16 track tape machine - which when plugged in to the desk creates hum in the system.
seeing as I use this most it is a big problem.

The way I have it set up at the moment is the Ampex is on the same breaker as the console, monitors and amp.

anyone got any suggestions which I should try?

[quote author="tardishead"]My system is extremely quiet and hum free - apart from my Ampex 16 track tape machine - which when plugged in to the desk creates hum in the system.
seeing as I use this most it is a big problem.

The way I have it set up at the moment is the Ampex is on the same breaker as the console, monitors and amp.

anyone got any suggestions which I should try?[/quote]

If you ampex have playback cable and record cable, if I remember, at one cable ground(s) of all chanels must be broken. Look to tape machine docs, it must be here.

xvlk

First suggestion:
Telescope the grounds to the tape machine, electrons get into the desk but they don't get out. Lift pin one at the xlr male that goes INTO the deck, leave pin one on the output of the deck to the desk. That way you aren't carrying noise to the deck, but are carrying it away from it. One day when you have more time and energy than you know what to do with try this one by one with your outboard and leave pin one off of any piece of gear that this makes quieter.
Suggestion B,
Ground lug on the deck? Get it to the patchbay, from there to earth. If you are using the power supplys to the desk as your ground instead of the patchbay get the tape machine there.
Final suggestion,
Unmentioned above in my other post was the notion of balanced power as your electrician would discuss it with you, this is a little esoteric and is going a long way for what may solve your problem, probably lower your noise floor but just as likely do nothing perceptible at all. When the electrician balances a system he tries to put approx the same current draw on each leg. Assuming that you have a box that splits one 220 phase into two rails of 120. It can be very helpful if you put your console (outboard too) on one side of the box and your tape machine on the directly opposite side of the box.
I live to serve, hope any of this helps. I always found trial and error to be my best problem solver once my logical solutions were exhausted, just stop when you think you may be getting into something lethal. Electrical grounding can be wild and mysterious, I have heard stories of people proper grounded to a deep copper rod who have to keep the copper lubed (pour water on it) or else they would lose their earth and buzz and buzz and they wondered why forever until they finally accepted that what they thought was zero was nothing of the sort.
I always told my interns that the first question they should endeavor to answer when they walked into a new facility was "What's grounded, to where, and by whom?"

copper.org has a few articles re grounding and some of the newer specs
under power quality. Also John Risch has a web page with a few ac tricks
but I am still curious why if you stand a right angles to the natural gas pipe
line that goes overhead in my studio it quiets the noisiest guitars??