Howdy!
Been a bit quiet on my side, thought I'd share my latest amp build. Pace was very slow on this one, have been working on it since July grabbing the odd hour or two whenever we got a break from the home renovations.
Anyway, My 18 watt Lite IIb has not seen much use since I finished my Trinity Plexi Brown. And there was an unused phase inverter input and space for another triode. What to do! Starting from this:
Simple design, single volume and tone control, cathode bias EL84 no negative feedback
The biggest learning curve in each of my builds has been how critical layout is. My previous Plexi 6V6 had layout issues that resulted in unsolvable noise problems. So the first month was spent with pencil, paper schematic and blank chassis trying to figure out where to put everything. This also helped me choose the design eventually.
The chassis had space for 4 input holes, five pots, an indicator and a switch. Hmm. Not quite enough for a Plexi. Decided presence control would go on the back of the amp. Plus, this helped my layout as this chassis puts the speaker jacks off to the side, which can result in parasitic oscillation with poor NFB wire placement.
At this point was thinking of doing a variation of SDM's 2203/1959 mod. But more on that next...
