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A low frequency hum is probably 60 cycle hum from the AC. If the
place had any dimmers on their lights, that alone would explain
it. Flourescents lights also transmit lots of 60 cycle hum, which
is tough to eliminate. You can experience this problem regardless
of how many outlets are provided. It is understandable when you
go into an old hall. Years ago, the most a band needed was a place
to plug in the accordian, and maybe one amp. Any new hall should
have plenty of power on stage, however, bear in mind that these
buildings are built by contractors who could care less about
any special requirements. They put one duplex outlet every so many
feet, period. If the hall doesn't make it a point to have extra
power put in, you get what you get.
My cousin uses some large spot lights in his stage act. One
place he played in had such a poor power setup, that the stage outlets
were on the same circuit as some of the kitchen outlets. At one point
the lights dimmed down, then came back blairing for a second, and he
blew out 3 bulbs in one shot. The bulbs cost around $15-$20/each, so
this set him back quite a few bucks. It turned out they had a
refrigerator plugged into the same circuit in the kitchen. When the
frig turned on, the lights dimmed, and then when it kicked off, the
surge caused the bulbs to burn out. At my suggestion, he purchased a
line conditioning transforer (also makes a good space heater/boat
anchor). He found that not only did this fix the problem of lights
dimming, but he noticed right away, that the lights seemed brighter
than ever, and stayed at one intensity all night. Think of a
transformer as a tank. If you pump water into a tank, and then pump
it out the bottom, the tank will eliminate any dips or surges in water
pressure.
As for 60 cycle hum, it is very tough to eliminate. Flourescent
light don't send 60 cycle hum back through the ac lines, they transmit
it like radio signals. The cords you use to connect guitars, effects,
etc. all act as antennas. The 60 cycle hum gets picked up by these
antennas and are send right into the input preamp of your amplifier.
The power supply in your amp works hard to filter out 60 cycle,
as well as any ripple, however, when you inject noise right into
a preamp input, it is gonna get amplified, period. A noise gate
placed right before your amp input is the only way of eliminating
this annoying problem.
Lately, I have seen a lot of line conditioning power supplies (rack
mountable type) in many music stores. They are great for protecting
equipment from line surges, However, if you want to eliminate 60hz
hum, you need a noise gate. Most noise gates have a threshold, and
effect your sound because they are constantly kicking on and off
depending on the level going into them. This creates an annoying
(breathing) effect which many people dislike. Some of the better
noise gates have a very minimal breathing effect. Look around.
Noise gates are a very good investment for a musician who finds
himself in a lot of older halls, or places where noise is a big
problem.
I won't get into single coil pickup vs humbuckers, even though
it makes a big difference in noise immunity, because I know that
both of your guitars are equipped with humbuckers.
Good Luck !
Mark
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| Other hum reduction tricks:
All cables are somewhat sensitive to 60 Hz hum, but better cables
(more shielding/foil shields) are less so.
Try changing the routing. It's bad to run parallel to an AC cord,
better to run perpendicular. Experiment, sometimes moving the cables
a few feet to the left can help. Othertimes, move three feet to the
right and sling it over the water-cooler.
Don't rip out that annoying little ground pin in your three-prong plugs.
Get an 3 to 2 prong adaptor (with the little wire for ground) and tie the
wire to the screw on the outlet.
Get plug strips with line filters ($7.98 at Spags).
Make a ~4" coil of two or three turns in the cable at the input (for a
guitar cord - at the amp, for a speaker cord - at the speaker, for an
AC cord - where it enters the equipment). This can help reduce common-
mode noise. I have to do this to the cable on the reverb pedal on my
Ampeg cause the cord picks up some radio station.
Disconnect everything except the mixer and amp. Try reversing the
polarity of the mixer two-prong plug. Is there more hum? Change it
back. Less or the same? Go on. Hook up the next item (the DDL, say)
and find the 'correct' polarity for it. Repeat until all the stuff is
in. This will help find the source of the hum, and may reduce it.
Enjoy,
Dave
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| Finding any outlets is usually a chore, as we often play outdoors,
or in someones home. There are a number of cures, some mentioned,
others are:
1) Carry long extension cords (I have 2 50 footers, and have
changed the 6 foot power cord on my Twin Reverb with a
16 gauge, 25 foot cable).
2) Put transient filters on all of your lines (they are cheap
& available from radio shack).
3) Find out what else is on your line. Recently when everything
was sounding like absolute cr*p, We found that the line
voltage was nowhere near 120 volts (the Mechanical HAMMOND
was the clue, it wasn't even close to being in tune). Always
try to find open power lines.
4) Don't use dimmers if you can avoid it. In my lighting system,
I use 12 amp/400volt stud mounted diodes (cut the voltage
in half when you select the DIM position). This takes care
of transients, and doesn't screw up the AC lines going into
your equipment.
5) Sheild everything. Don't use plastic covers on the 1/4" phone
jacks that you use (the metal ones can take being stepped
on - saves you money in the long run). My guitars have thier
insides sheilded thru either copper tubing, or copper plates
fitted into the cavities (I make my own guitars).
6) Carry a VOM (Volt Ohm Meter) around with you & if you get
your lips char-broiled, find out which amp is doing it.
7) Avoid ground loops. My power distribution box (for my effects
boxes) has a switch selectable ground for each effect. Since
my cables always provide signal ground, there is no need
to have the power supply add additional connections:
+----------+
| 9.5 Volt |----------+-----+-----+-----+--- + 9V
| 1 Amp DC | / / / /
| Wall Bug |---+ \10 \10 \10 \10 ohm 1/2 Watt
+----------+ | / / / / Resistors
| | | | |
| +--+ +--+ +--+ +--+
The O is the + 9 V out | | | | | | | | |
| +| O +| O +| O +| O
| =10 =10 =10 =10 uf 35v caps
| | | | |
+---+-----+-----+-----+------ - (ground)
Put in an on/off switch to connect the
ground to each connector.
Radio Shack has had the high power wall bug for $4.95 for some
time now & it has plenty of power for my stomp boxes (I have
8 9 Volt outputs on mine, as well as an LED POWER indicator)
Jens
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| I doubt if two speaker cabs would interact with each other, especially
if they are producing sounds in different frequency ranges (ie one
bass, the other guitar). I have never heard of two cabinets cancelling
each other frequencies out.
As far as electro-magnetic interference, again I doubt if it
could be a problem. Some companies make what they call Video Speakers
for home use. I asked someone once what was the difference between
video speakers and regular stereo speakers. The explanation I got
was that if you plan to place a speaker on either side of you TV
set, the high voltage operation of the TV could effect the speaker,
therefore, video speakers (suppossedly) have highly shielded cabinets
to block the effects of the high voltage. Who knows how valid this
theory is. Could be just another marketing ploy. I can't see how
two speakers could interact with each other and produce a low freq
noise problem.
Again, just my 2c worth, and I don't know if it is even worth
2c since the devaluation of the dollar.
Mark J.
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