Marshall DSL50 Valve Biasing.
When replacing or changing power valves in this amp or others like it, it is important to purchase a matched pair of power valves from your supplier. The power valves in the DSL50 are a `matched pair of EL34`s`. Which make you choose, is a matter of price and tone preference.
Then to see visually how simple the job is to do, log on to `Eurotubes` an American website where this kind gent has actually provided a video of the job being done. He also biases power valves in other makes of amp where the amp chasis must be removed.
Note : Valve amplifiers do produce high voltages (circa 500volts) within the internal chasis area. Marshall DSL`s thankfully have external reading/biasing pins at the external rear of the chasis which saves having to remove the chasis from its housing.
JUST WATCH THE VIDEO FROM `EUROTUBES` and you WILL learn a lot about valve amp tone, valves and correct biasing. It may be helpful for you to know that Marshall themselves set bias at 45mv (millivolts) for each power tube in the DSL50. They consider this the optimum `tone` setting for a Marshall DSL50 using currently Svetlana EL34`s.
I hope this pointer to Eurotubes will help you, as much as it did me. Regards, Taffy Strumitalot.