- 1). Remove all out-board effects and processors from your signal chain. Sometimes effects pedals can have a detrimental effect to the quality of the guitar signal, even when switched off. The best way to inspect the quality of your amplifier is to test it with a guitar going directly into the input jack. This approach immediately eliminates out-board equipment from your inspection.
- 2). Change guitar cables. A faulty guitar cable may be the cause of your pulsing problem. If the wire is slightly damaged, it can carry a signal but may intermittently fail. This may create a pulsing sound as the amplifier receives a strong signal then a weak signal.
- 3). Turn down any on-board effects. Many of the modern Fender Twin amps feature on-board tremolo and vibrato effects. These effects are used to create volume swells in the guitar signal, similar to rotary speakers. If the amplifier is turned up loud, the normal hum from the amp may swell. Turn down the effects and listen for any pulsing. If the pulsing goes away, you'll know that the pulsing is a natural side-effect of using the effects. If it remains, further investigation is required.
- 4). Use the amplifier in another property. Often the cause of unwanted sounds in guitar amps comes from poor wiring in the home. Light switches and other currents can interfere with the operation of an amplifier. Take your amp to a friend's house and monitor the pulsing.
- 5). Remove the rear panel of the amplifier and vacuum clean the interior. Dust particles that collect inside the amplifier can conduct current from the tremolo unit's low frequency oscillator into the audio path.
- 6). Remove the amp chassis from the cabinet and inspect the insulation on the wiring. According to electronics engineer and guitar effects expert R.G Keen, the problem could be linked to the wires. On certain models the ground wire shares a terminal with the wire that runs to the vibrato unit. Damaged or broken insulation can cause the signal from the vibrato unit to leak into the signal path, causing a pulsing sound even when the vibrato is set to zero.
- 7). Check for solder blobs. Poorly executed soldering can create solder bridges between two parts that should not be connected. If a solder blob is touching another part of the amplifier, it may create a buzz. If the solder blob is intermittently connecting the two parts, for example when the speaker vibrates, this can create a pulsing buzz sound.
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