This could be any of several things. IF the audio output of the mic is at a normal level then the first thing to check is the mic cable. I have several things to discuss so read all of this and then test.
First, I found six BRAND NEW XLR cables were wired wrong... the vendor had 13000 of them in stock and was going to have to check them all. The cables appear to work, but had the shield and one signal wire in the wrong place so the line was NOT a twisted pair balanced as required, but instead a plain coax. I had to repair these at a venue when I discovered the problem. Please google the correct XLR configuration. The pin numbering is NOT what one would expect. You cables (open the ends and look) should have the shield tied to pin 1 which is one of the side pins. Mine they had the shield on the middle pin or apex of the triangle.
Second, there are COUNTERFEIT Shure SM58's being sold. Read about that at google... If you unscrew the screen and find a label on the side of the element, the mic is a fake... Now there are two qualities of fakes... some perform ABOUT as good as the genuine, and others don't even have the balancing transformer.
If the hum is only there while handling the mic, the ground to the shell is not connected... this is mainly a mechanical connection. You can extract the XLR male plug from the bottom of the mic by removing the side screw and gently pull out by grabbing one of the pins. Also you can verify the wire colors as the fakes use the wrong color wires.
Noise problems are my specialty so if you need further help send a comment to me.
i just got one from ebay. The sound is so low it's unreal. the crappy mics i have are louder. I did a few checks like u said and the wires are green and black? There is a label with caution on the neck on the mic when u take the top off. I guess i've been sold a fake? as far as im concerned as the sound is so low it's faulty in my eyes so will attempt to send it back. let's see what happens.
I had low level hum - the cause was that the mic was too close to an active loudspeaker. Moving the mic away fixed the hum.
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Unplug your
receiver.. Split a wire and attach one of the splits to the receiver
where you will see the text, "ground" or something similar. Attach the
other end to something metal such as a pipe that goes into the ground.
Secure with electrical tape. Plug in.
connect the ground wire to a screw on the electrical
outlet.
There is a TSB for this problem. Here it is.
Bulletin No.: 04-06-02-007
Date: August 11, 2004
TECHNICAL
Subject:
Low Engine Coolant Level Indicator Always On (Diagnose Low Coolant Level System
Operation/Check Sensor for Oil Contamination)
Models:
2000-2002 Buick Century, Regal
2000-2001 Chevrolet Lumina
2000-2002 Chevrolet Impala, Monte Carlo
2000-2002 Pontiac Grand Prix
2000-2002 Oldsmobile Intrigue
Condition
Some customers may comment that the low engine coolant level
indicator is always illuminated.
Cause
The cause of this condition may be due to engine oil
contaminating the coolant. Possible sources of oil contamination are internal
engine leaks, improper service procedures, or the addition of some types of
anti-leak additives to the cooling system. Once in the coolant, the oil leaves
deposits on the level sensor creating an insulating film. This film results in
a false activation of the coolant level indicator.
Correction
Diagnose low coolant level system operation and check the sensor
for oil contamination using the procedure listed below.
Important: No coolant supplements should be used in GM cooling
systems, other than what is approved and recommended by GM. The use of
"aftermarket" over-the-counter sealing and cooling supplements may
affect the operation of the low coolant level sensor. Discoloration of the
coolant recovery bottle is normal and does not necessarily indicate that
coolant contamination is present. Flush cooling system only when instructed by
this bulletin.
1.
Verify that the coolant is at proper level in the radiator and
the coolant recovery bottle. If the coolant is low, add proper amount of 50/50
water and DEX-COOL(R) mixture. If the low coolant light operates properly,
diagnose the cooling system for loss of coolant as outlined in SI. DO NOT
proceed further with this bulletin.
2. Remove the low coolant level sensor. Refer to Coolant Level Module Replacement
in the Engine Cooling sub-section.
3. With the key on, the engine off and the coolant level sensor disconnected
from the vehicle wiring harness, observe the low coolant light:
^ Light is on - Chassis wiring or instrument cluster concern.
Follow the appropriate diagnostic information in SI.
^ Light is out - Proceed to Step 4.
4. With the key off, connect the coolant level sensor into the vehicle's wiring
harness. Connect a ground wire (1) to the battery negative terminal. Using a
sharp probe (3) attached to the ground wire, ground the coolant sensor probe
(2) as shown in the illustration. Make sure a good contact is made. With the
key on and the engine off, observe the low coolant light for at least 15
seconds.
^ Light is on - Replace the low coolant sensor and re-check
system operation.
^ Light is out - Proceed to Step 5.
5. Using a small wire brush or emery cloth, polish the low coolant level sensor
probe to remove any film or oxidation. The probe should be a bright brass color
when finished. Use Brake Parts Cleaner to flush removed deposits from the low
coolant sensor probe. Re-install the low coolant sensor into the vehicle and
proceed to Step 6.
6. Flush the cooling system and install new DEX-COOL(R) mixture as outlined in
the SI. Check the vehicle's warranty history to determine if any engine gasket
had recently been changed. If there has not been a recent gasket replacement,
locate and repair the source of the engine oil contamination.
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