Samson Wireless - Boss

GT-X Setup Manual

Turn the amp volumes down (or switch to standby on amps
like the Mesa Boogie MKIV), and bring the foot volume
back to minimum. Connect up the stuff. Turn your amp
back up again. There will be a small amount of hiss coming
from the GT-3/5. I'm afraid to say that the noise you hear is
that of the GT-3/5 itself. There isn't much you can do about
this.
Now rock forward on the GT-3/5's pedal. Glug. A lot of
noise arrives in the form of hiss. Turn on the noise
suppressor—the hiss should return to the same level with
the foot volume down. Turn the NS off again. This level of
hiss you are now hearing will only be present on patches
that use extreme high gain and I personally wouldn't
recommend that. Bring the volume pedal back to zero. Turn
the guitar volume to zero—make sure it really is.
Then plug the guitar into the GT-3/5. Now bring the volume
pedal back up again. The noise you get should be precisely
the same. If so, then that's good. If it isn't then you need to
work out if it is your guitar, the cable or the GT-3/5 itself.
Try another guitar, try a different cable and so on. My GT-3
sounds the same. If anyone gets a different result from this
then please let me know. Bring the foot volume back to
zero. OK now don't play anything and turn up the volume
on the guitar. Gently bring up the foot volume. I don't
recommend bringing it up too far as you will start to
feedback—I get about half way before I give up. There
should be no more noise than was individually generated by
the GT-3/5 or your guitar straight into the amp. Great.
Things are shaping up.
OK, I am fairly happy the Guitar -> GT-3/5 -> Amp set-up
is now OK. So I'll press on with the rest of my equipment.
Volumes down and unplug the GT-3/5 including from the
power supply. Keep the equipment down to just the Amp
plus whatever we are testing at the moment.

Samson Wireless

My Samson Wireless is rated at better than 100dB below
full volume. i.e. -100dB so I am not expecting any new
noise from it. The Samson wireless has two outputs one
XLR one 1/4inch jack. If I use a balanced XLR -> 0.25"
jack cable to the input on the GT-3, the input level drops by
12.5-25%. The sound is also a lot thinner. Just be wary of
such set-ups and try to avoid them.
OK, all volumes down. Power off and unplug the GT-3/5. I
have the wireless transmitter off. I plug the receiver straight
into the amp. Volumes up again. Argh! I get a mains hum.
Instantly suspecting a ground loop with no evidence I try a
broken shield cable. No difference.
Hmm. So now I decide to go through the GT-3/5. Again
volumes down in between checks. Plug the GT-3/5 in with
'Noise Check' dialed in. Nothing in the input. Amps up.
Foot Volume forward to remind ourselves of the noise we
© Copyright 2000-2002 Barry S. Pearce et al.
Section 9
expect with no volumes up. Plug in the wireless and feed
the output signal to the GT-3/5. Volumes up—should be no
change. Any problems here might indicate a problem
between the GT-3/5 and the wireless. Well. There is no
change—the hum is still there! (you get the idea anyway). I
now replace the GT-3/5 to amp cable with a broken shield
cable (broken at the amp end). Wow. The humming has
gone. I've had a ground loop somewhere.
What had happened here was I hadn't yet come up with the
advice I gave about drawing a diagram to help identify
ground loops. I hadn't realised the rack would be acting as
one giant ground! Even though the wireless system has a 2
wire power lead, it was being earthed through the rack.
Thus if I disconnected the Samson and put a cable direct
from the guitar -> GT-3 the noise came back! I did say
funny things can happen with electronics. The basic rule I
found was that with the guitar directly cabled to my GT-3 I
require full normal cables to the amp. But if the Samson is
plugged in I require broken shield cables to the amp.
The solution is insulating the equipment from the rack.
There are two parts to solve here. Firstly to stop the front
panels of the units touching the rack, and secondly to avoid
the fixings (the screws) from defeating the first part's
solution.
This is how I did it.
To solve the first part I purchased a bicycle inner tube, and
cut out two pieces. Each piece's length was the height of the
rack. I then split each piece down 1 side. Each piece was
then wrapped around one-side of the rack sub-frame (where
the screw 'pods' are). This was then Superglue'd to the rack
along the outside front edge. Looking down from above the
rack, the vertical profile of what I have done looks like this:
_____ —inner Tube
/
| {{}} —screw 'pod' which the screws go into.
|OOOOOO—rack sub-frame (
\_____^—Super glued on this edge!
Front of Rack
I then cut holes for each of the screw points on the rack.
These holes were square and were roughly the size of the
screw pod opening. If you just slit the tube, rather than
create a hole, then when you put the screw in and tighten it
up it snags the rubber. So make sure the holes are a little
larger than the screw. Part one of the problem solved. As
the front facia of the rack equipment are fitted in front of
the inner tube you don't even notice that its there. Being,
black the inner tube is quite hard to see. BTW, inner tubes
are chalked inside. Remove this chalk dust with a damp rag
before putting it *anywhere* near your equipment.
Noise Elimination
51