Special thanks to George Nichols and Brunswick Amplifiers for providing this photograph.
|Years||1965-1967 (maybe as late at 1968)|
|Power||4x 7189A (two pair for stereo)|
|Power Bias||fixed bias|
|Vibrato||3x12AU7, 12DW7, 8 varistors|
|Phase Inverter||2x 12DW7|
|Speaker||2x 12" Oxford Alnico 16ohm (spring-fall 1965)|
|Speaker||2x 12" Jensen C12P 16ohm (fall 1965 and later)|
|Output||2x 38 watts peak|
|List Price||$580 (1965)|
The M15A is a 1965 replacement of the M15, please see that page for details of the M15 circuit. This page only addresses changes to the M15.
See the M15 and M15A reverb comparison for a complete review of reverbs used on these amps.
Both the M10 and the M15 received preamp design overhauls in 1965. The 1963-1965 M15's contour switch with "mellow", "normal", and "bright" settings, was immediately following the first gain stage of the preamp, and the entire preamp was 2 7025 gain stages with volume and tone in between.
The new design moves the contour switch to a RC circuit selector after the second stage and uses half of an additional 7025 to make up the gain loss in the RC circuit.
I think this preamp circuit might have first been used on the 1959 190 "treble plus".
The new Custom Series lineup for 1965 does away with any amp that doesn't have a 12" or 15" speaker. The M15's two sets of 8" Oxford and 3" tweeter speakers are replaced by 12" Oxford Alnico speakers, which, sometime in the fall 1965, were replaced with Jensen C12PS ceramic speakers (M10 8"/3" pair gets treated to the same 12" replacement).
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 as a retail price. The nickname, "The Pulverizer" was light-hearted and aimed at a youth market.
The earliest M15A schematic I've found has a release date of 3/23/65. This coinsides with the timeframe of the switch from the M15 to the M15A date codes I've collected. For more on this subject, see Dating Customs.