I have an '85 model 4210 1X12 50 watt combo, channel switcher with reverb and effects loop. My on-line research of this model told me that my amp has the un-desireable "diode clipping circuit" that Marshall introduced in the 80's. Some would say this circuit produces a fuzzy, thin distortion. When I took my amp to my tech today and had him convert it from 6550 power tubes to EL34 he checked it out and said my amp does not have this diode clipping circuit. How cool is that !!! Could my amp have been one of the earlier model 4210's that was produced without this diode circuit ? Researching on-line pretty much says all model 4210's (combo version of 2205 head) had this circuit. Is there anyone out there who would know enough about Marshall amps produced 22 years ago who could tell me if it is possible to have a model 4210/2205 without the diode clipping circuit, or is my technician full of it ? Thanks man !