(Mods: I put this in Accessories yesterday, but I'm not sure if it should go there or here in Amps. You can delete whichever doesn't belong)
I have a 4-space rack case made by USA Case (Michigan). I don't think the company exists any more. I bought this rack case in '93. I housed my Hartke 3500 head and rack tuner in it with no qualms whatsoever. It's 18" deep, black carpet, HD plastic corners and front & back lids. Made of plywood.
The lids seem kind of cheesy, but they work. Any head like the Harke would fit, although the space between the rack rail and lid is kind of shallow. It isn't made for heads that have the big handles on it, the lid won't fit. I think about 1" or 1-1/4" between the rack rail and lid is about it, just enough for the knobs of the amp to fit. I can measure it for sure. Has one handle on the left side.
It's a really tough case, I've giged with it extensively and never had a problem. Weighs about 8 pounds I think.
$40 shipped
