I just uploaded a profile of my Marshall Studio 15.
Its an amp I used in the mid to late 1980,s.
It uses 6V6 output tubes and has a unique sound.
I remember the filaments or heaters of the tubes had their own DC supply to reduce hum.
It was designed for studio use and that is just how I used it.
Its up on Rig Exchange now.
[Blocked Image: http://www.amparchives.com/Amp%20Archives/Marshall/Miscellaneous%20%20Valve%20Combos/4001%20Studio%2015%2015W%201x12%20Combo/85%204001%20Studio%2015%2015W%201x12%20Combo%20SN%20T37001/87b5_3.jpg]