Mesa/Boogie Three Channel Dual & Triple Rectifier Solo Heads, Руководство пользователя, Страница: 11 / 18

SYMPTOM
NOISE (LOW FREQUENCY HUM) IN AUDIO
1. Defective instrument cable or problem with bass wiring. Plug a very short instrument cable into the instrument input (to turn the
DI-PREAMP on), if hum is greatly reduced or eliminated, this means that the noise is entering from outside the DI-PREAMP. Try
a known good instrument cable and/or bass).
2. If using the XLR outs, try switching the ground lift switch on those in use to eliminate any inadvertent ground loops between
connected devices.
3. Disconnect audio feeds from the DI-PREAMP to the noisy equipment and see if the noise goes away. If it does not, the noise is
being generated or introduced external to the DI-PREAMP.
4. If the volume level of the hum changes with position of the bass (rotating or general movement), the problem may be external
stray magnetic field present that is coupling into the pickups, especially single coils. Possible causes are large power transform-
ers located near the performance area. If this occurs when you get close to another instrument amp it may be due to stray field
from its power supply. Moving the offending amp further from your pickups is a possible solution as the pickups and the offending
amp’s field is the issue, not your DI-PREAMP.
SYMPTOM
NOISE (HIGH FREQUENCY HISS AND HASH) IN AUDIO
1. Defective instrument cable or problem with bass wiring. Plug a very short instrument cable into the instrument input (to turn the
DI-PREAMP on), if hum is greatly reduced or eliminated, this means that the noise is entering from outside the DI-PREAMP. Try
a known good instrument cable and/or bass).
2. Defective battery in active bass or DI-PREAMP causing excessive noise (replace battery).
3. If there is neon or fluorescent lighting close by, it’s possible that EMI (electromagnetic interference) is radiating into the pick-up
wiring. Arcing secondary wire on neon lighting or a failing ballast or tube on fluorescent lighting may be radiating EMI into instru-
ment pick-up. Try turning off such lighting to see if noise goes away.
4. Disconnect audio feeds from the DI-PREAMP to the noisy equipment and see if the noise goes away. If it does not, the noise is
being generated or introduced external to the DI-PREAMP.
5. Tweeter turned all the way up in a quiet room, especially if the sensitivity of the tweeter greatly exceeds that of the low frequency
drivers. Turn tweeter down is these conditions.
SYMPTOM
NOISE (POPPING) IN AUDIO
1. Popping while playing, especially one string. Check bass set-up to be sure there is adequate clearances between the string and
pickup pole pieces.
2. Popping while just sitting there, or when touched. Under dry environmental conditions, it’s possible that electrostatic discharge
is the cause. Try antistatic mat on floor or a humidifier in room.
3. Popping while moving cables or connectors indicates that there might be a defect in those cables or connectors. Replace cabling
with known good and working cabling.
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