Mismatching the the OT Secondary on an EL-34 Express

[Curbdog]

I am thinking now about EL-34s in my Express, using the 6.6K tap on the OT, and mismatching the secondary. Any reasons not to do this? I would set the impedance selector of the amp at 8 ohms, and using a 4 ohm cab, the tubes will see 3.3K. I understand that this should be safe for a 2 - EL-34 amp, and that 50W Marshall Plexi's can run at 3.3K. Any concerns with an Express? I for one am not worried about it being too loud ! Cheers

[Nigel Tufnel]

The higher than normal impedance of the ot is a big part of the sound with an express imo. Mismatching the load is certainly not needed for your output tubes to be happy, if I remember correctly the standard marshall ot impedance of around 3.4k was an error in the first place. Something like old el34 data sheets recommending a load in that range for el34's running in triode, can't remember where I read that but I think it was posted by Chris Merren and he knows a good bit more than me about ot's. The higher z helps to roll off highs and the express makes plenty throughout the gain stages, it may very well cut your head off with treble running a more marshall like load. But if it sounds better to you that way then that's all that really matters at the end of the day. The best thing boards like this can do is breed experimentation and ideas, have fun.