You see, I bought a Sunn amp thinking I could get that Leslie West tone, and he got it out of a 4 or 5 knob Sunn amp, maybe modified yes, but I thought if he could do it with a Sunn amp, then I would like to get that tone too. I didn't realise until I got my Sceptre that it was vastly a clean sounding amp.
Anyway, I took the casing off the attenuator, and underneath the slider switch, there is a label, and it states for each position; 2x, 4x, 8x and 16x. The 16x I am sure refers to 16 ohms, which aligns with the X. Oops! Looks like I had the attenuator set for 16 ohms, instead of 8. So the amp was being worked twice as hard! Ah well. We all make mistakes, I'm just glad I didn't leave it on for much longer and burn out the input transformer, it only overheated.