11 Feb
2015
11 Feb
'15
3:58 a.m.
On 02/10/2015 05:43 PM, Len Ovens wrote:
As an aside... I don't think I will need it at
this point, The isolation
boxes that are easy to get are "DI" boxes tha go from high impedance
unball to low impedance bal. Would these still work to go from a
ballanced output to an unballanced input?
DI boxes are designed to connect an unbalanced output to a balanced
input. I've also pondered running DI boxes "backwards". From a
technical view, I'd need to study the schematics of the driving
equipment, the DI box, and the driven equipment to convince myself that
it could work and not damage anything. I might try calling technical
support. From a execution view, I'd need the right adapter cables (such
as XLR-F to XLR-F). But from a conservative/ safety view, I'd rather
hook everything up the way the equipment manufacturers tell me to and
not have to worry about it.
Or do I need a one to one
isolator? Or does it depend on the powered monitor?
I'd look in the monitor manual and follow the manufacturer's
instructions. If you don't have a manual and can't get direction from
the manufacturer, I'd use an isolation transformer with suitable
connectors and cables.
How does this one look:
http://www.rolls.com/pdf/M_HE18.pdf
That looks useful.
Having "solved" my problem with a single
power source, would it still be
worth while isolating all stage amps from the mixer?
If the mixer has balanced outputs, the stage amplifiers have balanced
inputs, and both are powered from the same supply, isolation
transformers should not be necessary. I'd run balanced cables from the
mixer to the amps and call it good. That said, good isolation
transformers will cause a small lose of signal and fidelity, but they
might provide protection for certain equipment failures or operator errors.
I think I will run
ballanced audio through the snake and do the cable adapting at the stage
end anyway.
It is best to keep balanced signals in balanced cables for as far as
practical.
Right now there is a TS plugged directly into a TRS
mixer
output which means the signal minus is grounded.
I wouldn't plug a TS cable into an balanced TRS output. First, you are
shorting one half of the balanced driver output circuit. Second, you
are injecting chassis ground noise into the audio circuits.
There are two unused
(unusable) snake lines I could use where we have the DVD and computer
plugged in as line level.
Hmm, more thought required, the DVD/computer may need changes too.
I assume the DVD and computer are unbalanced. If those are next to the
mixer, cables alone might do. Check your mixer manual. If the runs
aren't local and/or you can't find an authoritative wiring diagram, I'd
use DI boxes.
David