level signals. (Try unplugging effects from effects loop, if the distortion disappears, try the effects between the bass and the
input of the amp.)
4. Slightly intermittent cable in system (this can be an instrument cable, patch cable or loose screw in SpeakOn plug)
5. Defective or blown speaker(s) in cabinet (test with known good cabinet, repair cabinet as needed)
6. Possible failing tube/valve in preamp. V1 is common to both preamps, V2 is exclusive to the Boogie channel, V3 is exclusive
to the Subway channel. (substitute with known good 12AT7 or 12AU7)
7. Possible incorrect tube/valve installed in preamp. These circuits are designed for use with 12AT7/12AU7 tube types. 12AX7
tubes do not have enough drive capability to work well in these circuits and will result in decreased levels, dynamic range and
increased distortion. (replace any incorrect tubes with 12AT7/12AU7 types)
8. There is indeed a problem with the amp, call our customer service department and we will help you get this resolved.
SYMPTOM: Noise (low frequency hum) in audio:
1. Defective instrument cable or problem with bass 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 bass)
2. 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.)
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. 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 bass. 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)
5. Some cell (mobile) phones can emit strong bursts of RF energy as it communicates with the towers. This is a potential source
of randomly appearing noise. (locate the phone farther away from the bass and/or amp, switch the phone to airplane mode
or shut it off entirely.
6. This amp model contains tubes/valves in the preamp, it’s possible that you are experiencing the beginning of a tube/valve
failure (replace tube/valve one at a time with a known good tube/valve to see if this resolves the problem)
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
(possibly an active preamp with the treble turned all the way up, a failing battery, defective on board preamp)
2. This amp model contains tubes/valves in the preamp, it’s possible that you are experiencing the beginning of a tube/valve
failure (replace tube/valve one at a time with a known good tube/valve to see if this resolves the problem)
3. If there neon or fluorescent lighting close by, it’s possible that EMI is radiating into the pick-up wiring (try turning off such light-
ing to see if noise goes away. If so, it could be arcing secondary wire on neon lighting, failing ballast or tube on fluorescent
lighting, radiated EMI getting into instrument pick-up)
4. Some cell (mobile) phones can emit strong bursts of RF energy as it communicates with the towers. This is a potential source
of randomly appearing noise. (locate the phone farther away from the bass and/or amp, switch the phone to airplane mode
or shut it off entirely.
5. 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.)
6. 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.)
7. Tweeter turned all the way up in a quiet room (may need to turn tweeter down under such conditions, especially if the sen-
sitivity of the tweeter greatly exceeds that of the low frequency drivers with tweeter turned up)
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