My first gig rig for bass was a '74 Hiwatt DR103 through a vintage Kustom 2x15 tuck 'n' roll cab. Nice sound actually and still have both the amp and cab, though i gig with other cabs these days. I had gigged guitar, sitar, and keyboard/piano prior to my first time gigging bass.
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I realize this post is old, but I'll respond anyway. It sounds like you had a Hiwatt DR112. These are great amps, quite rare too. There's a pic of one here:Huge modified Hiwatt 100 watt head and a Hiwatt 4x12 cab. The head was configured more like a p.a.
Very strange thing.
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