Hammond didn't actually make their own tubes. They are probably rebranded GE or RCA. Some are also Mullards. I think tubes make a huge difference in tone, though people disagree. A GE 12AX7 is clean and level to my ear, an RCA has a little more sparkle and grain, and a Mullard has more warmth. For Jerry tones I like RCA long blackplates for preamp tubes and clear RCA 6v6 power tubes. With Vox-type amps I use a Phillips short-plate and Polam EL84s. If you want a middy hump, Amperex Bugle Boys are great. Pricey though.