Mesa Rosette 300 Two:Eight, Owner'S Manual

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SYMPTOM
NOISE (LOW FREQUENCY HUM) IN AUDIO
1. Defective instrument cable or problem with instrument wiring (unplug instrument cable from amplifier, if hum goes away, this
means that the noise is entering from outside the amplifier. Try known good instrument cable and/or instrument)
2. Power source wiring is not grounded/earthed (check all wiring for missing grounding/earthing pins, have qualified electrician
check building power wiring for missing ground/earth connections and correct as necessary.)
3. External stray magnetic field present coupling into the pickups, especially single coils (one clue that this may be the cause is when
the volume level of the hum changes with position of the instrument. Possible causes are large power transformers 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)
SYMPTOM
NOISE (HIGH FREQUENCY HISS AND HASH) IN AUDIO
1. If the noise goes away when the instrument cable into the amp is unplugged, the cause of the noise is external to the amp (pos-
sibly an active preamp with the TREBLE turned all the way up, a failing battery, defective on board preamp)
2. If your amp model contains a tube/valve in the preamp, it’s possible that you are experiencing the beginning of a tube/valve
failure (replace tube/valve)
3. Power source wiring is not grounded/earthed (check all wiring for missing grounding/earthing pins, have qualified electrician
check building power wiring for missing ground/earth connections and correct as necessary.)
4. Problem with wiring or a device in the effects loop (remove send and receive wiring from the amp’s effects loop to identify the
source of the noise, correct as necessary.)
5. Tweeter turned all the way up in a quiet room (may need to turn tweeter down under such conditions, especially if the sensitivity
of the tweeter greatly exceeds that of the low frequency drivers with tweeter turned up)
SYMPTOM
PROTECT LED TURNS ON
1. Disconnect all cables except power cable, if the amp is no longer in protect, try plugging in just the speaker cable. If the amp
goes immediately into protect, one possible cause is a defective or damaged crossover that is presenting an illegal load to the
amplifier and the protection circuit is working correctly.
2. Protect circuit shuts down amp while playing at low to moderate volumes (possible shorted speaker cable, try known good speaker
cable, possible low AC power source voltage, amplifier is protecting itself from damage)
3. Protect circuit shuts down amp at moderate to high volumes (possible low AC power source voltage, amplifier is protecting itself
from damage
4. Power source voltage falling dangerously low due to improper wiring or extension cable that is too long for its wire size. (correct
problems as needed with the help of a qualified electrician)
5. There is indeed a problem with your amp, call our customer service department and we will help you get this resolved.
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