I just got my brand new marshall sv20h, but I notice there is noticeable noise when I plugin to treble holes. (both jumping cable or use treble individually) but the normal channel is dead quiet. I use 2 greenback speakers, 25 watt each. 1, when I unplug-in any cable, it is silent. 2, when I just use normal channel, it is quiet. 3, when I plug into treble channel, the hiss (white noise) starts at volume 1.5, increases with the volume up to 4 and then will not increase much when volume is over 4. 4, Treble, mid, presence can affect the noise level a little bit. here is the video link: So, the question would be, is it a common situation on this amp? If not, how can I solve it?