I just repaired a Blackface Bassman head that has a very late 1965 xfmr set (543, 539, 545) with a AA165 label, and rubber stamped “13” (no letters). It has been converted from a bias balance ckt to adjustable bias. The chassis is also rubber stamped “4665” between the bottom of the PT and the eyelet bd. What might the “13” signify? It’s definitely two numbers, not two letters. It’s not the normal two-letter stamp like in my ’65 Deluxe Reverb.

That cabinet is likely a Tremolux cabinet,

You would have to look inside at the wiring to determine which circuit is correct. I’ve never heard of AA185, or 10″ speakers in a Bassman. All piggy-back Bassmans had two 12″ speakers, until the big cabinets with 15s became available in the Silver Face era. Either your information is skewed, or the unit has been modified. Don’t pay too much for it.

I am thinking of buying what is being called a 1966 Bassman head and cab, and I’m confused about several things. First it has a AA185 tube label so shouldn’t that make it a 1965? And secondly, it has 2 10″ Upton speakers which the owner believes are the origin as they are stamped 39th week of 1965. Again – a ’65 or a ’66? And I thought they only made the cabs with 1×12’s during that time… Thanks very much for your help.

I have a ‘66 bassman at 4 ohm now can i hook up a 4×12 cab at 16ohm? So one 16 ohm cab into my ‘66 bassman at 4 ohm