"U-CDK_CHARLES
Patrick Dunford

Every sound system manual I have ever seen recommends strongly you have
dimmers on a separate phase from the sound system.

The problem with this is, most dimmer packs are three phase.

Short of not using 1/3 of your channels, what can be done about the
noise
problems?

The manuals are talking about studio installs, whereas dimmer packs are
"luggable" in that context.


** The manuals are talking about sound systems - not studios of any kind.


When I was doing theatre, they'd bring in 200+ channels of dimmers.
These would be wired direct very close to the service entrance with the
ground lead doubled, making a very robust earth connection.

The sound equipment would then be effectively "separate" . . a much
smaller load usually a service panel or two removed from the lighting.


** AS recommended in the manuals Patrick is reading.


The "dimmer problem" is most often encountered in a residential or
commercial space that's retrofitted into a studio.


** Is anyone so dumb they have triac dimmed lights installed in a
recording studio ????


Residential dimmers have to meet emmission standards sufficient for TV
viewing,


** AM and short wave bands are covered too - just not the AUDIO band !!



If the power distribution is well-planned and the dimmers are of better
quality (variacs, hopefully), this is less of a problem.



** Variac and variable inductance dimming went out decades ago.

For critical applications, where no audible buzz can be accepted there are
modern "Sine Wave" dimmers - using either mosfets ot IGBTs to "chop" the AC
at supersonic high frequency and scale it to any desired value.


http://www.stld.org.uk/php/index.php...&contentid=176




.............. Phil