|Years||1965-1967 (maybe as late at 1968)|
|Power Bias||fixed bias|
|Speaker||12" 16ohm Oxford Alnico (spring-fall 1965)|
|Speaker||12" 16ohm Jensen ceramic C12PS (fall 1965 and later)|
In 1965, the M10A was introduced as a replacement of the 1963-1964 M10. With a speaker change and a preamp overhaul, the amp much more attractive to guitar players, and a much better competitor to the Ampeg Gemini I. While the M10 was one of the most popular Custom Series amplifiers, the M10A's demand made it an enduring favorite until some time in late 1967, or possibly early 1968.
For the guitar player, the most significant change of the M10 to the M10A was the replacement of the Oxford 8" speaker and a 3" tweeter with a single 12" speaker. The first M10A's came with Oxford Alnico's. In the fall of 1965, Estey switched to 12" Jensen C12PS ceramic speakers.
There is also a subtle but important difference in the preamp sections of the M10 it's successor, the M10A. Both have a three position "contour" switch, but while the M10 places this switch circuit directly after the first preamp stage, and the M10A places it after the second gain stage and uses a more complex set of RC circuits to affect tone. These added RC networks require a third stage 12AX7 to make up gain before heading to later parts of the circuit. So, while the M10 requires two 7025 tubes for its two preamps, the M10A requires three 7025 tubes for its two preamps.
I think this preamp circuit might have first been used on the 1959 190 "treble plus".
Like all Custom Series amps left in the catalog for the 1965 re-vamp, the gold control panel and gold grill cloth is changed to a polished aluminum look with silver grill cloth.
This is a dealer brochure from sometime in 1966 showing what the dealer paid, and what was suggested for a retail price. The nickname, "The Wrecker" was light-hearted and aimed at a youth market.
Incredible product placement by Magnatone. Four happy nuns with Starstreams and an M10A
Steve Luckey's M10A page, contains good gut-shots and redrawn schematics for the M10A.