Recording studio wiring

[SirKit Breaker]

I did one a few years ago for Pye Hastings of Caravan (yes - still going). 6mm SWA from house, industrial combined class surge protection unit (absolutely essential), then standard 32A ring and 6A lighting circuits from a garage CU. Only problem was the dimmer for the CFL spotlights which started buzzing in B flat. Replaced that with a switch and everything has been fine since. As far as I know, the audio earth is well isolated from the mains earthing on good kit so no exceptional earthing measures are required. If it's good enough for a man with gold discs on his wall, it's probably good enough for your mate.

Cheers
Chris

You cant beat keeping it simple, nice one.

Cheers..........Howard

 

[UKMeterman]

Hi,
I would suggest taking a look at Tim Williams' book EMC for Systems and Installations I do not suggest single ended bonding of screens as this can cause more issues than it solves. The customer may be gettinng shocks because of lifted earths on equipments and so on. The correct way to solve these earth loops is to provide a parrell low impedance path to the signal wires, and also ensure that any supply cable has the current return in the same cable, so the loop size is kept down.

I would also suggest looking here EMC Information Centre and have a look at EMC for systems and installations. A lot of the noise can be reduced by proper selection of propper cables and connectors.

There has been mention of an AUDIO earth, what currents are you expecting down that particular rod? Why isn't that rod bonded to the mains safety earth?

Regards

UKMeterman

 

[chrishaworth]

Audio earth = DC 0V.
Cheers, Chris

 

[UKMeterman]

If it is at 0V then there is no currrent...... please take a look at the website pages above. It discusses what is true earth and what isnit..

 

[chrishaworth]

That's like saying a neutral at 0V relative to earth is taking no current. Electronics uses terminology in a different way to LV AC.
Cheers, Chris (ex Electronics Officer).

 

[UKMeterman]

Hi,
Yes I am aware of the difference, most pro audio equipment is designed for a signal to noise ratio of 120 db or more. The signal voltages may be a 1v or so in the respect of line connected equipment CDs and the suchlike and about a 0.0001 of a volt for a microphone, thus the noise voltage should be kept 120dB below these, or 1millionth down. The major issue is that the shield on single eneded connections is also connected to the mains safety earth at both ends, and touch currents and similar can try to flow through the shield. If say the shield of a poor cable had a resistance of say 0.5 ohm, and say 2ma tried to pass that way then there would be 1mV of noise. The trick is to get this common impedance down, use good quality cable with a good braided shield, Vandam cable and nutrix connetors would be good. If need be run another CPC in parrell with the signal cable if the 50Hz hum is a problem.

The audio equipment is only concerned about the voltage it sees at the inputs, if the shield is connected to a ground rod (which will have a significant impedance anyway) it is not releivant

Regards
UK Meterman BEng(Hons.) MSc MIET

 

[chrishaworth]

Now we've established that neither of us are first year apprentices, we can continue the discussion. My main contention is that professional recording equipment does not normally require specialist earthing arrangements etc. In fact the more you pay, the better the filters will be. Rather than paying out a fortune in dual CUs etc., the OP would be better off spending on sound insulation. If the equipment works fine when plugged in at the house, then it should work OK in the studio.
Cheers, Chris

 

[UKMeterman]

Hi,
My point exactly, you just need to think of some basic ohms law, and if there is a hum where could it come from. The main point is do not disconect any mains safety earth from any bit of kit. It may be an idea for some local equipotenial bonding with a nice large earth block and and some 4mm2 connected to each rack by the shortest route. If the OP wants any more ideas please drop me a line.

 

[chrishaworth]

I must have been incredibly lucky that the one I did worked with no problems.
Cheers, Chris