Dating vintage fender amps by serial number
All models have a push-pull (class AB) dual 6L6GC power amp configuration.Up to the blonde Bassman with blonde colored tolex (circuit 6G6) they all had tube rectifier, but since then a diode rectifier was used.If you disconnect the NBF loop you’ll notice that the volume increases and tone gets much more aggressive. Not only is there a volume shift, the amp’s clean headroom is reduced slightly.Most importantly the tone gets rougher and rawer with more mids and higher frequencies, aka presence.The bassman was a combo amp in the tweed era with the 1×15″ and 4×10″ speaker configurations.From the blonde era Fender made the Bassman as a amp head and 2×12″ closed cabinet. The video below compares a Bassman AB165 to a Princeton Reverb and a Deluxe Reverb.
It was introduced in 1951, primarily targeted for bass guitar players and promoted as a bass amp for the Fender Precision Bass guitar, the first mass-produced electric bass guitar ever.
1) Combining the AB165 and AA864 The schematics for this amp is explained below.
The red circles in the schematic below illustrates these changes.
During the different eras the Bassman amp came in many different shapes and configurations.
Few other models experienced so many changes in terms of looks and tone.
We’ll come back to this later in the “blackface chapter” below where we’ll demystify some of the hypes with the popular AA864.