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Well, since I'm getting my Marshall soon I've been thinking about getting a new instrument cable, because my old amp hums ALOT, and I suspect it to be the cable, because when the cable is disconnected there's almost no hum at all, and I don't want that with my new amp.

So, is this a quality product (I've heard that they are, but I don't know)?.
The model I've been looking at is either the PW-G-30 or PW-G-20 (the same cable, just difference in length). The plugs are with gold, and the cable is double insulated/double shielded.

Any decent cable will do you, but if you want to spend the money, get the Palnet Waves. I suspect this hum has to so with something other than your cable though.

Maybe, I don't know, I could of course always try with this cable first and see if there's a problem.

planet waves are good quality cables, very reliable in my experiece too, go for it, always good to have a spare anyway.