I haven't watched the one on cabs yet but that one about guitar amps totally nails it. The design of the tone section, the gain stages and most importantly, the speakers, make up 50% of the tone, with the guitar pickups and the player's actual style making the other 50%.

There seems to be no shortage of snake-oil salesmen out there. He needs to do one on pickups soon. (stupid quack pickup makers are one of my pet peeves) There's so much misinformation when it comes to pickups and so much bogus crap being sold with misinformed, non-scientific marketing, it's ridiculous! Definitely subscribed to his channel.

That's a nice explanation of the cab-sim. I'd always thought they were only for recording or plugging direct into a sound board. Now it's making more sense.

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.

How did I not notice this sooner? Yeah, I read that interview. Those amps have now jumped a 'decade' in price all over ebay, craigslist, etc. I remember my sweetheart was doing opening sets at a lot of metal shows about 10-12 years ago. A lot of the junior shredders were showing up with low-end Peavey amps like these. They get great sound when they're mic'd.

This reminds me of that Jimmy Page interview many years ago, when he revealed that he did the entire first Zep album with a Tele and a 22-watt Supro amp. Little Supro amps of every description skyrocketed in price afterwards. They do sound great though, as do those little Peavey Decades.

What I want to see is a pedal based on the Heathkit TA-16. Now there's a unique sound.

Great thread! Thank you for sharing your progress. I hadn't realized that the Pathfinder 10 was such a simple circuit and  all thru-hole to boot. Wishing I'd kept mine now. Eliminating that ridiculous 'Boost' section is a great idea. I never found it to be realistically useable. I'd thought about re-homing mine in a new cabinet with a decent speaker (8"or 10") but never got around to it.

At 18 watts you've got the perfect amp for small club gigs. Currently, that's mostly what there is around here. (besides some occasional busking) Hipsters in our neighborhood want wallpaper music to hang out to so little amps like this are really useful. I hope you'll have some sound samples for us in the near future.

At this point I'm switching to building something for guitar. (and maybe vocals) Going to put the TDA2003 board to good use, I hope.

Still haven't made progress with this project yet due to being sidetracked with other problems. I've decided that building a busking amp for just the guitar or maybe guitar and vocals would be a better approach for now.

I was considering using this Blues Breaker pedal kit as a guitar preamp. (I like the sound)

https://www.musikding.de/docs/musikding/breaker/breakerschalt.pdf

I already have a premade TDA2003 board around that I could use for a power amp.

https://www.jameco.com/z/VM114-Velleman-7W-Amplifier-Kit-Assembled_2151881.html

Or I could go with this TPA3122 kit to have a channel for guitar and a channel for a mic. 

https://www.parts-express.com/Sure-AA-AK32151-2x15W-Class-D-Stereo-Power-Amp-Kit-TPA3122-320-322

I was just wondering if I would need a buffer between the Blues Breaker and the power amp board?

Thanks for the advice on the TPA3116D2 and the TPA3122D2N. I will definitely look into those. If I use it with a trimpot controlling output I should be able to conserve battery life and avoid ugly clipping as well, no? I will probably use the TDA2003 module I have here for just a guitar amp. 4 watts with a good speaker and a good preamp should be enough for guitar alone.

Thanks for the advice. I'll definitely keep searching for ideas. I would just go out and buy a ready made system but I'm not liking the look of most of what's out there. Speakers are always too small (for bass) and usually too few inputs. A mixer section is definitely something I'm thinking of. Possibly adding a reverb for vocals as well. As for power tool batteries, I've got a couple around here but I'm doubtful of their current capacity. They've been sitting unused for some time. Might just go the gel-cell route.

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.

Nice stuff! That is a very unique and original look you've got going on there. Not an easy thing to achieve, nowadays. I like how it looks almost Cold War Industrial. Your labeling technique is clever. Very cool!

Well, I finally got my hands on one! A Gretsch Gadabout. Canada Customs or somebody in handling had managed to destroy the Jensen C8-R that was in there. Coil had been completely torn from the magnet and the cone was mangled. Had to have happened when the package was opened and "inspected" by some overpaid goon. 

Anyways, tried it out with an Eminence 12" I had around. Sounds great! Flat, but nice, like an old Standel or something. Breaks up nicely when the volume is full. Will post a sound sample when a replacement speaker arrives.

I will also post some gut shots. I've only used it on AC mode so far. The battery leads are cut, and now I'm not sure of the correct polarity. Standard grounded chassis would make sense, but this thing is from the Germanium era, so could it possibly be reverse? I definitely want to get this puppy running on batteries if possible!

For speaker efficiency, have a look at some decent quality ceramic speakers. The "vintage-tone"snobs seem to love alnico, but those speakers are seldom as efficient. If you can find the full specs (including the all-important SPL rating and frequency range) then you can get some idea.

Eminence make really efficient speakers, full specs available. So do Weber. (but they don't publish their full specs) Also, decide on which speaker size works best for you, tone-wise. The larger the speaker, the better chance of it being more efficient. Lots of loud 15-inch, 12-inch and even 10-inch speakers out there. 8-inch or smaller and you're starting to lose out.

Read lots of the reviews online. They may seem subjective, but they've usually steered me right. Anyways, Eminence and Weber both make great sounding, loud speakers.

Well, eventually I will come across one of these at a reasonable price. (the smaller Gadabout model usually goes for $100 - $150 on EvilBay or Craigslist) I really liked the sounds I heard from these amps. Very Vox-like. If there is no schematic paper pasted in the amp, then I will probably be posting gutshots.