amplifier hum question.
Tim
play at various venues around a tri-county area. OK, so I went up town
to hear them Sat. and one member and I got to tlaking on their break
and he asked me so i thought I'd try to get some ideas here.
One place they play is an older brick building with everything that
can plague an older brick building.
I'm sure the wiring is sub-standard and I dont' know if it has
fluorescent lights causing fits or not. But all the amps and PH have a
"hummmmmm" that they can't get rid of. The guitards amp hums the
worst. Not totally obnoxious, but really annoying.
It seems that today's equipment(for the most part) doesn't have any
provisions for a "reverse" switch on the amps, and with three-prong
plugs it's kind of hard to do the old "turn-the-plug-around" trick.
Even with a reverse switch, I've seen instances where when flipped the
hum only got louder.
The manager says all the bar/ kitchen equipment is in good order, ,
but that's left to be seen.
So my question is, does anyone here know of any type of device/ power
bar etc, that can help compensate for this type of a problem?
it's a good gig for them but event the patrons come and ask them
"what's the hum?" They don't know, I don't know.
Any ideas?
Thanks!
Golem
.
>
> I'm sure the wiring is sub-standard and I dont' know if it has
> fluorescent lights causing fits or not. But all the amps and PH have a
> "hummmmmm" that they can't get rid of. The guitards amp hums the
> worst. Not totally obnoxious, but really annoying.
>
The geetard may be the hint. GT's are addicted to
single coils. It may be an airborn signal causing
the hum ... generated somewhere in the building,
but NOT entering the amps thru their AC cords.
An airborn hum can be picked up directly by the
circuit wiring or the PCB tracks within the amp
but most often it's picked up by the stuff attached
to the input jack [instrument and input cord]. Not
only are geetards addicted to SC PU's but pedals,
all that extra crap attached to the input jack of the
amp will likely act as an antenna for airborn hum.
You are a basser [your read this board ... ]. Test
each amp with a tioadally humbucking, preferably
full active bass. Unstrung would be a bonus. If the
bass makes less hum than the instrument usually
on that amp, it's airborn hum.
Also, if the geetard can increase or decrease his
hum level by orienting his neck/strings in various
directions/angles, then he's steering or aiming his
antenna, and proving that it's airborn hum.
Golem
for that. At least one SC-addicted, hum-plagued
"tone purist" is grateful for this:
Geetards usually learn that their strings are the
antenna, and that they can aim the antenna to
somewhat reduce airborn hum. I even recall a
tune that got titled "West" cuz in the studio, the
guitar had to be aimed to the west or the hum
was too much for recording.
- - - - - - - - - - - - - - - - - - - - - -
OK. Important info follows here:
Always test direction with the neck lifted up to
your usual playing angle, and then be sure to
maintain that angle while playing.
- - - - - - - - - - - - - - - - - - - - - -
Explanation [if you care ... ]:
Geetards tend to hold a neck VERY horizontal
when seeking the least objectionable direction,
as if taking care to get accurate data. It SEEMS
to make sense, since if held fully vertically, the
neck/antenna would be omnidirectional with no
lesser or greater hum from any direction. But
since no one plays vertically, they do their hum
direction checking dead horizontal.
Well, horizontal is about 60 to 90 degrees off,
compass-wise, for a player who keeps the neck
at a fairly high angle. At a 45 degree angle it's a
full 90 compass degrees wrong [relative to the
test result with the neck held horizontally].
A straight antenna [like your strings] has three
basic 'receptive postures':
VERTICAL: Nondirectional, omnidirectional.
FULL HORIZONTAL: Maximum directional effect,
strongest at right angle to the antenna.
45 DEGREE: ["half horizontal"]: Only about half
as directional as full horzontal, but directional
effect is NOT at right angle to antenna. It is now
shifted 90 degrees from there, and so effect is
strongest WITHIN the plane of the antenna [NOT
perpendicular as with full horizonatal].
As you can see, hum testing at horizontal, but
then playing with the neck at a 35 to 45 degr of
lift, is not gonna work out too well, hum-wise.
Tim
Thanks for the replies Golem. I also wrote a friend of mine who is a
player and an electrical engineer and here's what he wrote back to
me...
--------------------
You may need to experiment at the venue and with the owner's help to
identify the source of the problem. Tell him that patrons are
complaining and you want to see if you can cure it.
I think it depends on the source of the hum or 60 hertz noise.
If it's RFI radiating from lighting fixtures like florensent lights
or
other ballast type devices, you should be able to tell by simply
turning the lights off temporarily. Older equipment in the place
could
also be introducing it either via RFI or on the AC line.
With the owner's permission and help, set up an amp with a guitar
plugged in, turn up the volume until the hum is very noticeable and
then, one by one, have someone turn off each circuit breaker in the
power distribution box. See if any of them dramatically reduces the
hum and then see what electrical device is powered from that breaker.
Older electrical appliances and equipment can actually introduce 60
hertz hum in the power lines, particularly if they draw high currents
when running.
http://www.federalpacific.com/literature/drytrans/10transformernoise.pdf
Another possible solution is to power the band's amps through one or
two devices called an "Electrostatically Shielded Isolation
Transformer". These transformers do not step the voltage up or down.
They are used to isolate the load side from the primary voltage
source. I'd check with a local electrician regarding the use of them.
They need to be sized appropriately for your equipment's current
draw.
Another possible solution may be to use a power conditioning unit.
"Monster" and others build units that have both active and passive
filters in them. They are typically used in higher end home theater
or
audio gear applications.
Here's some info on isolation transformers:
http://www.audioholics.com/tweaks/connec....em-hum-and-buzz
and here's some info for those of us that like screwing around with
old, vintage guitar amps and have lived to talk about it:
http://www.instructables.com/id/Isolatio....ld-guitar-amps/
Benj
> On Jan 3, 8:55 pm, Tim <tschna...@gmail.com> wrote:
> > I'm sure the wiring is sub-standard and I dont' know if it has
> > fluorescent lights causing fits or not. But all the amps and PH have a
> > "hummmmmm" that they can't get rid of. The guitards amp hums the
> > worst. Not totally obnoxious, but really annoying.
This could very well be a bad wiring/bad grounding problem. Start by
trying one of those line ground testers. They are cheap and if it
doesn't read 100% OK, raise hell with the owner! A miswired ground
can KILL YOU! Don't fool around with one. If there is still hum you
might rent/borrow a large line conditioner just to see what it does.
> The geetard may be the hint. GT's are addicted to
> single coils. It may be an airborn signal causing
> the hum ... generated somewhere in the building,
> but NOT entering the amps thru their AC cords.
If it's single coil problems try both pickups on full with your J bass
or have the geetard flip his Strat to a position using two pickups. If
the hum disappears (or gets much less) then it's single coil hum
pickup. If that's the problem look around for large transformers and
magnetic devices like ballasts. Often there may be some electrical
gear like that which is there to run the kitchen equipment. If that's
the problem, try to find the source by turning things off one at a
time. Correcting the problem is not so simple since you may have to
move the sensitive instruments (geetard, J bass) to some other part of
the stage or play in a weird orientation. Could be a nifty gimmick for
a rock band, though! :)
Steve Freides
> Start by trying one of those line ground testers. They are cheap and
> if it
> doesn't read 100% OK, raise hell with the owner! A miswired ground
> can KILL YOU! Don't fool around with one. If there is still hum you
> might rent/borrow a large line conditioner just to see what it does.
Post a link to one, please, and thanks.
-S-
Benj
That thing in front of you is a computer. Try Google to find things.
By the way, you want a true "conditioner" as I've shown not the cheapo
"surge protectors" that really amount to little more than MOVs
connected across the sockets. They will do little to kill spikey hum.
Andre Majorel
> I'm sure the wiring is sub-standard and I dont' know if it has
> fluorescent lights causing fits or not. But all the amps and
> PH have a "hummmmmm" that they can't get rid of. The guitards
> amp hums the worst.
Another possibility is that the mains voltage is really low for
some reason, so low that some 100/120 Hz ripple makes it
through. Easy to diagnose (AC voltmeter on the wall plug), not
so easy to fix.
If the amps don't hum when no cord is plugged in, the hum is
probably radiated by a fluorescent light, a dimmer or some such.
--
Andr� Majorel <URL:http://www.teaser.fr/~amajorel/>
"Marque nouvelle. Dans le stock. Les navires de FL, les
Etats-Unis. Service de client exceptionnel garanti."
Steve Freides
I was looking for a link to a tester, not a conditioner, which you said
were cheap. The things I find with Google are testers but they aren't
cheap, an "entry level kit" for $1200.
-S-
Benj
> I was looking for a link to a tester, not a conditioner, which you said
> were cheap. The things I find with Google are testers but they aren't
> cheap, an "entry level kit" for $1200.
Oh! Sorry. {one minute please] OK. Here are the kind of things I was
talking about. Cheap and excellent to flip one in the bass case.
These testers are to detect errors in ground wiring. (which make the
circuits potentially dangerous). The expensive testers are for
measuring the resistance to the ground stake. Those would be for
someone actually repairing a problem. What a musician needs is one of
these cheapies to plug into the wall to give some kind of warning as
to whether you are going to be electrocuted if you touch your guitar
and some ground (mic stand, metal supports, etc) conductor.
Steve Freides
Well, those are a _lot_ cheaper, that's for sure. I had just googled
exactly what you said, "line ground tester" and at least the first
several entires were the expensive stuff.
I played guitar for a show at the local high school this past summer,
and the bass player and I both got shocked if we touched each other's
instruments - not good, and especially not good at a public high school.
(They simply didn't have a guitar player up to playing the chart for
Sweet Charity so my son "volunteered" me.)
I think I'll look for something like this at the local hardware store.
-S-
Steve Freides
This, BTW, was the first Google hit I got for "line ground tester" - it
shows on the main page as "entry level kit" and then here is the link to
the actual product - _everything_ at this site, and a few others, was
$800 or more, some several times that.
http://www.groundtesterstore.com/p3500/aemc_3620_(150ft_kit).php
-S-
Misifus
An inexpensive device such as this one,
is useful in determining if there is a wiring fault in the outlet to be
used. I use one ever since some friends fried several amplifiers,
including a prototype.
-Raf
--
Misifus-
Rafael Seibert
Photos: http://www.flickr.com/photos/rafiii
home: http://www.rafandsioux.com