Note: We now have a new, superior solution to Marshall JCM2000 hum, noise, and bias drift issues. Find the details here.   Marshall JCM2000 DSL100 Hum after warmup fix   There are a couple of key problems with the Marshall DSL can TSL series printed circuit boards.  One is the drifting bias due to board leaking current.  This causes the EL34 output valves to overheat,We sell  Stable bias board kits for  the DSL and the