The Fender Twin Reverb she’s referring to is the one Rachel fixed in this comic.

Also, for those of you who do not know, guitar pickups are the part of an electric guitar that “pick up” the vibration of the strings and convert it into an electrical signal.  As such, they are pretty fundamental.  In fact, they are what makes an “electric” guitar “electric”.

After drawing that JCM800 a few days ago, I really got the hankerin’ to get back to working on amplifier projects.  I’m purposely delaying my big 50W project I posted photos of earlier (until I figure out exactly what kind of preamp I want to put in it), but in the meantime I’ve been inspired to put together a JCM800 like the one featured in that comic, but with only about 5W of output power instead of the usual 50W or even 100W.

I still plan on doing a class-AB push-pull power amp, but I’ll use smaller pentodes (6AU6 tubes, to be exact) instead of the big beam power tubes used in the big amps.  That accomplishes two things.  First, having a class-AB power section (as opposed to class-A) means that there is the potential to have some “tube sag” in the power supply when big transients appear in the signal (if I design my power supply right).  Second, and more importantly, I can use this smaller, simpler power amp as a design exercise to prep for actually finishing that 50W monster I started earlier.

This amp should be small enough that I can fit it all on a single PCB, which I’ll probably etch at home.  It isn’t going to be a terribly complicated circuit, but PCBs are a lot easier to assemble than point-to-point, and though point-to-point is technically better for signal integrity in a lot of cases, it doesn’t make much of a difference at audio frequencies.

Anyway, I’ll post the design as I work it out.  The preamp will basically be the same as the standard 2204 JCM800 lead, but the power amp is going to require some work (and math!), so that’s where the fun happens.  Nobody really uses these tubes for power tubes (except for a few hobbyists I’ve found on forums – apparently they work, so that’s good), so I can’t “cheat” and copy a standard design like I can for an EL34 or 6L6 design.  I have to do all the calculations and design myself.  It is going to be fun.  I haven’t done any real, math-intensive circuit design since school.

Anyway, enough of my yakkin’.  See y’all on Tuesday!