I recently bought an Electro Harmonix 22 Caliber micro amplifier on Ebay, mostly out of curiosity. Yes, this thing is incredibly small and from the video it looks like it works pretty well for guitar: http://www.youtube.com/watch?v=59f-nIupDzg But I wanted to know if it could be used as a bass "head". First of all this thing is TINY, even with the tabletop style power supply included. It has only a volume control and a bright switch; there is no on off on the unit or power supply. There are power on LED's on both the amp and its power supply. On the unit it says"8 to 16 ohm speaker only", the manual and on the video say 4 ohms is okay. I tested this using my ATK 750 which is an active bass capable of a pretty wide range of tones. For speakers I have a Fitzmaurice DR250 and Tuba24, also an EV 15" , part of a'70's B15. With the bass straight to the 22 Cal. through the DR250 alone, the sound was very thin and dry (like my first wife). I tried a bunch of different pedals in front of this amp to fatten things up. Unfortunately I have already traded my VT Bass away in anticipation of getting the VT Deluxe. Probably a VT Bass would be the best match. I tried these pedals and pre's: EHX Knockout, BBE Sonic Stomp, Aphex Bass Exciter, Ampeg SVP Pro, Sansamp BDDI and a Nathan East-Yamaha NE 1. Basically they all worked pretty good tonewise and it was just matter of taste which one to pick. Predictably, if the volume control on the 22 Cal. was too high things would start to get muddy and then distort on the low notes. Here is where it got interesting; when I connected the T24, this little amp actually got into pants flapping range. The single 15 had similar results to the DR250 by itself. Some conclusions: It sounds a lot better with a 4 ohm load. It needs some kind of eq to sound good. It never got above room temp no matter how hard I spanked it. It survived a complete smoke test due to my sloppiness hooking things up such as shorted output, no speaker connected, connect speaker while on. Every time I screwed up it went into the protect mode and reset safely on power down. Is it a cool little amp or a pricey toy? I don't know. Until I figure out how to build an inflatable speaker cab, no matter how small the amp is you are still stuck with a relatively large box to carry in order to take advantage of its surprising power. One last idea: given all that empty space in the 22 Caliber's case, it seems to be begging for a Flipster circuit to be shoehorned in there, which would make it a compete Pico bass head.