Paul J. Morstad's Mesa-Boogie Adventure 3/'01

*... a retro mod to a modernized tube amp ...*

Pictures and Text 2003(c)JC Maillet

Mesa "Son-Of-Boogie" Schematic

... when Paul contacted me about his Mesa SOB 2x6L6 amp he didn't like the sound and unresponsive feel of the amp ... he inquired about getting his amp modded so I asked him to send me a schematic and further inquired about his tastes in players and experience with amps and guitars ... turns out Paul likes Jimmy Page's classic middle-periode tone, which is not an over the top distorted tone ... of course, Page was and is a Marshall amplifier player mostly - so the possibility came about reconfiguring his Mesa chassis into a 50watt Marshall MkII replica of some sort ...

... after settling on configuration options, we agreed to give it a go ... even though I'd never seen one of these before, the work went ahead and I used my Dremmel to carve out new trace arrangements on the existing pcb board ... the surgery took a week and it went well ... out came this sweet and responsive amplifier with good note definition and natural tone ... also with more power and a higher aggression level ...

... the mod features : (i) a Fender style power supply for a lively-er amp, (ii) EL34 power tubes, installing EL34's in a made-for-6L6 output transformer produces richer harmonics in the output stage, (iii) dual mode, Master Volume control - both Standard Configuration (with added ground lift) and Ken Fischer style Master Volume Controls for subtle variation a, (iV) a true single-channel front end ... in many ways it's still a conservative amplifier, but IMAO the tone with a Paul is *very much* worth the effort in the end - I strongly recommend going retro with EL34's on this chassis ... more info to follow ...

"... the Marshall metal face comparison; that was based on some messing around I did with a 50w head that belonged to a friend. It was a bass amp model for American export (powered by 2x6550's?), circa ~'72 or '73 as I recall -I'm fuzzy here, it might have had 2x6L6's in it, I don't remember. Anyway, there's a certain similarity between that amp and your retro mod to the Boogie..."

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