Having built only pedals before, my first venture into something that could be called a solid state "amp" was the Ruby from RunOffGroove. It is one of a family of related little 9V or 12V chip amps - Little Gem, Smokey, Noisy Cricket, etc. - all built around an LMN386 or similar. The Ruby differs from the Little Gem by having a buffer & some other minor tweaks.
I found the instructions helpful; they included some minor mods, a few of which I tried out. Also since at one point I was contemplating an 18V version of the LMN386, I started wondering whether the bias for the buffer transistor's gate would need improving rather than just having the bias resistor go to ground. I know nothing at all about this but a lucky Google brought me to AMZ's page on simple buffers, and I added the "reference voltage" tweak at the top of that page to the Ruby's buffer. Along with that I raised the value of the bias resistor to 10M, again as suggested by AMZ. I ended up staying w/12VDC, but even then the changes to the buffer circuit seemed to make the amp sound moderately better to my ear.
And that's about all I can find to really like about the Ruby - the slight improvement in sound from fiddling with the buffer. While tweaking, I have been running it on a breadboard with a 12" speaker from a Yamaha combo. The circuit is not noisy at low gain despite all the jumpers. But the amp suffers from what I would consider a rather crude breakup (if that's the right term) - it sounds similar to but not quite as appealing as the AMZ dirty boost pedal I built some time ago. The buffer moderates this breakup making it a bit more constant and fizzy, with which low gain at 12VDC is OK; but it is still very inconsistent, e.g. more breakup the higher up the neck you go, which is frankly weird.
The next step in my various little projects has always been to build a finished version - and I was all set to do that, when I stopped & asked myself, why? This amp is anything but versatile. If the tone could be moderated with pedals that might help a bit, but the Ruby doesn't seem to like pedals much: RunOffGrove warn you in their FAQ that anything but unity out of a pedal will overdrive a 386-based amp, and I can tell you from experiment that the result is unpleasant. Putting a passive tone pedal on, followed by just enough boost to get back to unity, didn't work work at all. A reverb pedal worked OK so long as I kept the volume low to minimize breakup.
So probably I will not build it, but disassemble it. I am starting to accumulate so many parts that at this point I really need to organize them better - right now I have "big box of caps" and "big box of resistors" plus "other box of resistors" plus "bigger boxes here & there that I just throw hardware into," etc. You get the picture. But with as many parts as I've got, it is becoming slowly easier for me to build small circuits here or there without having to order absolutely everything fresh. Just a question of what circuits.
I didn't have super high hopes but after reading the glowing descriptions at RunOffGroove for the Ruby and elsewhere for the Noisy Cricket, it seems apparent that some guitarists are able to take pleasure from a simple amp more easily than I can. My only consolation is that from what I read, should I keep muddling my way along w/ SS, apparently this is the lowest level of circuit, and other amps and preamps can sound a lot better.
Crude schematic below with my minor changes from stock Ruby - also I included polarity protection w/parallel diode plus fuse in main branch.
I found the instructions helpful; they included some minor mods, a few of which I tried out. Also since at one point I was contemplating an 18V version of the LMN386, I started wondering whether the bias for the buffer transistor's gate would need improving rather than just having the bias resistor go to ground. I know nothing at all about this but a lucky Google brought me to AMZ's page on simple buffers, and I added the "reference voltage" tweak at the top of that page to the Ruby's buffer. Along with that I raised the value of the bias resistor to 10M, again as suggested by AMZ. I ended up staying w/12VDC, but even then the changes to the buffer circuit seemed to make the amp sound moderately better to my ear.
And that's about all I can find to really like about the Ruby - the slight improvement in sound from fiddling with the buffer. While tweaking, I have been running it on a breadboard with a 12" speaker from a Yamaha combo. The circuit is not noisy at low gain despite all the jumpers. But the amp suffers from what I would consider a rather crude breakup (if that's the right term) - it sounds similar to but not quite as appealing as the AMZ dirty boost pedal I built some time ago. The buffer moderates this breakup making it a bit more constant and fizzy, with which low gain at 12VDC is OK; but it is still very inconsistent, e.g. more breakup the higher up the neck you go, which is frankly weird.
The next step in my various little projects has always been to build a finished version - and I was all set to do that, when I stopped & asked myself, why? This amp is anything but versatile. If the tone could be moderated with pedals that might help a bit, but the Ruby doesn't seem to like pedals much: RunOffGrove warn you in their FAQ that anything but unity out of a pedal will overdrive a 386-based amp, and I can tell you from experiment that the result is unpleasant. Putting a passive tone pedal on, followed by just enough boost to get back to unity, didn't work work at all. A reverb pedal worked OK so long as I kept the volume low to minimize breakup.
So probably I will not build it, but disassemble it. I am starting to accumulate so many parts that at this point I really need to organize them better - right now I have "big box of caps" and "big box of resistors" plus "other box of resistors" plus "bigger boxes here & there that I just throw hardware into," etc. You get the picture. But with as many parts as I've got, it is becoming slowly easier for me to build small circuits here or there without having to order absolutely everything fresh. Just a question of what circuits.
I didn't have super high hopes but after reading the glowing descriptions at RunOffGroove for the Ruby and elsewhere for the Noisy Cricket, it seems apparent that some guitarists are able to take pleasure from a simple amp more easily than I can. My only consolation is that from what I read, should I keep muddling my way along w/ SS, apparently this is the lowest level of circuit, and other amps and preamps can sound a lot better.
Crude schematic below with my minor changes from stock Ruby - also I included polarity protection w/parallel diode plus fuse in main branch.