I've been looking at these 14-Watt amp kits from Nightfire for a while. They have a few different versions but only the PT2399 Delay version has schematics available.
https://vakits.com/guitar-echo-effects-kit
I'm assuming the other versions are similar, minus the delay circuit. The designer was thoughtful enough to include a buffered input. Nice to see a small SS amp kit that actually appears to be designed with a guitar in mind.

I heard one clip of one of these cranked up high and it sounded pretty good. I liked the few sound samples I was able to find but I'm wondering about adding in another gain stage or two so the amp could get a little bit of light breakup a little sooner. Could I do this using FETs maybe? Would it be best to add a stage or two before the tone stack or after?

I suppose it would be nice to mod the delay section a bit as well. It appears to have most of its control options bypassed.

I've been building pedals for years now and built several guitars over the last few decades but I've never built anything amp-wise other than a very dirty sounding little LM386 amp.

My sweetheart and I were trying out and admiring our neighbors' Yorkville portable/rechargeable PA. It's the ultimate thing for busking. Can handle a guitar, bass and microphone all at once. (while disturbing the entire neighborhood for a 3 block radius) Runs for at least 4 hours on a charge. Wonderful thing, but the $700 price tag is just out of our range for something that would only get used for a handful of gigs per year.

I'm sure I've got at least one or two TDA2003 power amp kits around here somewhere. Rated at 10 watts or something. I was going to use a FET based amp-sim kit as a preamp along with an 8"/25-watt guitar speaker. (there are some nice, efficient ones available now) That would take care of my guitar well enough for busking.

I have a 2x/bridged TDA2003 kit here as well. Claims to be 20 watts. If I used that, with preamps on two separate inputs, would that be enough for bass and vocals? I was thinking of using a 10" bass speaker (Eminence has some nice ones) and maybe a smaller speaker with a crossover as well. (I know nothing about crossovers but it would be a good thing to learn) Would I need more power for busking with bass?

Would I be better off using the 2xTDA2003 amp as the guitar amp? Would I be in danger of blowing the 25-watt speaker?

Also concerned about current consumption. There are 12-volt gel-cell options and there are now plenty of lithium-ion options thanks to 10+ years of e-bikes everywhere.

http://www.ebay.ca/itm/1971-ELECTRO-HARMONIX-MIKE-MATTHEWS-FREEDOM-AMP-VINTAGE-ELECTRIC-GUITAR-AMP-FX-/310835229061?pt=Guitar&hash=item485f393185&_uhb=1

Electro Harmonix actually had a portable amp in the early 70s. Looks like it would stomp all over a Pignose.

Back in the `60s there were a couple of small SS amps made for Gretsch that could run off either mains power or batteries. Not sure who actually built them, as Gretsch didn't actually build their own amps. There was the Gadabout, which was just a small, super basic amp, with only a volume control. There was also the Safari, which was also small, like the Gadabout, but also featured a unique sort of tremolo circuit. I see these pop up on ebay sometimes, but they are always either selling for way too much, or else they are not available to buyers outside the US.

These were reputed to be actually quite nice sounding little amps. Producer Daniel Lanois has used them during recording sessions.

I've tried searching for schematics for them but no luck at all. Lots of stuff on the Gretsch tube amps, (all Valco made ones) but nothing on these. Anybody know if there are any schematics floating around for either the Gadabout or the Safari? If I can't buy one, I'd love to give a shot at cloning one.