| With an ordinary linear class AB amp you won't be getting a lot of headroom with just a 9V power supply. At cleans, expect about equivalent volume of loudly strummed acoustic guitar. If overdriven things can go louder but heavily overdriven tones generally aren't something you'd use with bass or acoustic.
So, I think all that will not work too well with bass or acoustic guitar. Those typically require some pretty good headroom.
So... assuming you really just want to use 9V supply, I would aim for bridged output section, not to mention designing for a 2-ohm load. Since it's battery-powered I'd also go for class-D output. Otherwise you end up with a low power amp (and in the case of not using class-D output, an amp that eats batteries on a good pace).
And you need a good set of speakers, suitable for the job. Those small ones you generally pair to this sort of stuff will ensure your amp just sounds like a soapbox with a weak, tiny speaker. Basically like a toy. You need good speakers to make the amp any good or useful.
So you'll be loosing all the weight/size advantages as well. There's reason why popular amps that work on gigs are big, heavy and (at least moderately) powerful, more so when amplifying acoustic instruments and bass. Those two are not equivalent to electric guitars that tolerate gobs and gobs of distortion. Instead they will need plenty of headroom and you can't get enough headroom with low power. You can't have your cake and eat it too.
If you seriously need a good tool for gigs I'd suggest buying one and wandering off the battery-powered designs to begin with. If you want something light, small and meh then building stuff is a nice adventure. It can likely also sound kickass with guitars, on bedrooms and on records. On bass and acoustic guitar... well... no.
Oh, one thing more: You won't gain anything special with discrete designs. Pretty much the contrary.
Last edited by teemuk : 11-19-2011 at 10:00 AM.
| 
