Hiss and hum: Marshall headJcm2000 dsl100. Doesn't seem as loud as it should be, and over the top hiss and hum when I crank up the volume. The amp is a floor model; about three-four years old. Could it be a tube issue?
Music - Marshall - Mg100dfx 100-Watt Combo Guitar Amplifier
Answers & Comments
More than likely you have a power issue. Look closely at the main filter caps. These are the 2 larger than the other caps. They are usually about 4700uf at 63v (generic values but yours should be close). Check them for swelling, if no signs of that then you will need to due a capacitance check on them. Sometimes but not always, they will show bad on an esr meter also.