I have a Marshall DSL40CR. It came with EL34's as the title says. I decided I wanted to try 6ca7's and was told they are essentially drop in replacements for EL34's. I had the EL34's biased at 35-36mv. When I put the 6ca7s in, I was shocked because the bias was 70mv. I lowered them down to 35-36mv.

My question is: Should the 6ca7's be biased to the same number I had the EL34's at? Should I go higher or lower? The reason I'm asking is that most Marshall techs say 35mv is where you should be at with EL34's to sound their best. Is this the same for 6ca7's?

There is also a very slight burning smell in the rear of the amp. Don't know if this is just something about the new tubes or if it's cooking the amp....sounds fine though.