Rather than reinvent the wheel, and end up with a flat on one side, take the advice of people on this page. The PRRI is a Princeton Reverb. It just has PCBs instead of a hand soldered tagboard, but the circuit is the same. A PR is a Princeton with reverb. A Princeton is a smaller Brown Deluxe with 10" speaker and tremolo. A Brown Deluxe is a Tweed with fixed grid bias instead of cathode bias. So if you build a 5E3 it's the simplest and.lightest 6V6 push-pull amp that's very easy to build because it's cathode biased. Once you have built a 5E3 you can progressively turn it into a Princeton - the 6G2 Princeton is probably the most revered small Fender. Even more so amongst cognoscenti than the PR. Fender builds a $3000 handwired version of this, the Chris Stapleton. And it has a direct lineage to a Tweed Deluxe. The Tweed Deluxe power and output transformer are straight into the ballpark for a 6G2. So if you build the 5E3 and get it working - and it's a great amp, built two myself - it's about a dozen components and half a dozen circuit changes. It has the right number of tubes, too You can build a 5E3:with a single input in a small chassis. Very easy. Someone posted a link to Rob's version. If you build a PR with no reverb or trem, you have a Princeton with no balls, because the PR uses a tube to push gain up because the reverb tank and circuit pulls it down.