All rights reserved. Design rights claimed. Moral rights asserted. Revised March 2010
Page 14
9. TheGigRig Pro-8s Isolated Output
Isolated output… Output 2
Let’s cut through the jargon, like earth loops and earth impedance and get right
down to the source of Hum.
If you have one Guitar into one effects pedal into one amp, you won’t get hum.
Although your power supply is connected to the mains, it won’t be connected to the
mains earth. Therefore, your precious guitar signal has just one path to ground;
through the screen of your leads into your amp and through to the mains ground.
The hum problem occurs when you have more than one path to ground for your
signal. Using two amplifiers has always been an issue, because they both MUST be
connected to mains ground; however, you only want one signal ground for your
audio!
TheGigRig Pro-8 has a very special output for your second amplifier, or any other
earthed equipment you need to feed with your signal.
Only use output 2 when you have already used output 1, that’s the golden rule.
Output 1 will provide your signal ground.
Phase Switch.
Phase switch with the same sound going to two amplifiers of different models. The
amplifier speaker cones could be either, moving forward at the same time (in phase)
or, one may be moving forward whilst the other is moving backwards (out of phase).
If this occurs then, when the sounds mix, the sound waves will cancel, giving a
reduced tone at a distance from the speakers.
To Change the Phase to match your amplifiers:
You will find a small button next to the isolated output (see 5 in Fig1). When this
button is pressed ‘in’, Out 2 will stay in phase with Out 1 and when this button is out,
yes you guest it, Out 2 is then out of phase with Out 1.
When you have set the phase correctly, you can then swap your two amplifiers
between out 1 and out 2, without causing a phasing problem.
For three or more amplifiers, please see our web site for a cost-effective humdinger
of a solution.
