Dating vintage ampeg amps
typically 400V or more, and a lower voltage for the tube filament, typically 6.3 or 12.6V. Dating Marshall Amps In 1969 Marshall introduced a date coding system.
Some of the older Marshall amps have an inspection sticker on the top of the chassis which usually has the day, month and year the amp was actually made or inspected. Note, "A" Date Code ran for 18 months (July 1969 to December 1970) so the "B" date Code was never used and has been omitted. The serial number is generally located on the back of the chassis but from 79 to 80 it was on the front panel.
Replacement tubes and transformers are readily available for these amps however there are many boutique amp manufacturers making new tube amps with a vintage sound.
A transformer is an electrical device that transfers energy from one circuit to another by magnetic coupling with no moving parts.
When hot, the filament releases electrons into the vacuum: a process called thermionic emission.From 1969 to 1983 the date code was after the serial number.From 1984 to 1992 the model number was first, then the date code, then the serial number.This is only a very brief overview and we suggest consulting additional resources if you are interested in additional information. Most good guitar amplifiers use tubes rather than solid-state components. The amplifier is a critical element in achieving the sound the musician desires. Tube amps are warmer, richer and have a more desirable tone than solid-state amps.The distortion and speaker-damping characteristics of a tube amp with an output transformer matched to the speaker load is hard to replicate with solid-state devices.