DIY Portable Amp <120$ - Page 2

AMB's parts pages usually have a gain section to indicate which resistors to change to adjust the gain.

The issue with batteries fitting is some 9v are a little fatter than others, and even normal sized ones sit basically flush with the lid on the hammond.  So if you use a battery a little out of spec you may have trouble squeezing it into the normal enclosure.

If you are dropping the charging circuit and planning to swap the battery often you probably don't want a hammond case.  Even if you got thumb screws it is still usually 6 screws to undo and then slide the top out on hammond cases.   You may want to look at the Serpac cases used in PIMETA builds.  You will need to look at internal dimensions to make sure you get one that fits the PCB and component heights (use the internal dimensions of the recommended hammond as guide).  Serpac should make something that fits.  The Serpac cases can have a battery compartment with a door and whatnot to easily pop a battery in/out.

The H65 is recommended for PIMETA's and has a 9v battery compartment option.  Don't know which case the Mini3 PCB will fit, but they make a veriety, so poke around the datasheets.  http://www.serpac.com/Products/Hseries/H65.aspx  

The Mini³ PCB was designed to fit the Hammond 1455C80x case perfectly and elegantly, with board-mounted connectors/volume pot/battery contacts/LEDs and no wires.  The board has no mounting screw holes, because it was intended to slide into the Hammond case slot.  If you use a different enclosure, even if it fits, securing the board will be a problem and you'll have to air-wire some connectors and the battery.  The wires will flex each time you open the case to change the battery, and eventually break from fatigue at the solder joints.

I also don't like the Serpac H65 case.  The original Mini³ prototype was made for the H65, but I found that the screw threads wear out if you open/close the case often, and the plastic just feels cheap and flimsy compared to the Hammond's aluminum extrusion.  The H65 is also significantly larger than the 1455C80x.  For these and other reasons I redesigned the production Mini³ to use the Hammond instead.