Special thanks to George Nichols and Brunswick Amplifiers for providing this photograph.
|Years||1963½ to early 1965|
|Power Bias||fixed bias|
|Reverb||12AU7, transistor recovery|
|Speaker||8" 16ohm Oxford AlNiCo.|
The M10 was probably the most successful of the Custom Series amps. These amps tend to come up for sale more than any other Magnatone of that era.
The M10 is a two channel amp each with "loudness", and "tone" controls in a Each channel has an additional "contour" which switches between a treble bleed circuit, and dumping high frequencies to ground ("bright", "normal", and "mellow"). This simple tone control design is a carry over from the earlier amps (213,440,etc) and is shared on amps like the contemporary M7 and M12. The M13, M14, and M15 all had Baxandall style tone stacks with "bass" and "treble" knobs, and the M10 would be updated to that style in 1965 with the M10A.
The is also a "stereo" input jack to use both channels with a single instrument cable (read more about that at Stereo Inputs ).
The M10 makes use of the F.M.Vibrato four varistor vibrato, which was more advanced than the two varistor vibrato used on some of the less expensive Custom series amps ( M2, M4, M6 ).
The 1963 M10 reverb circuit is an updated carry over from the reverb used used on early Magnatones (like the 480). A 12AU7 drives the Hammond reverb tank and a transistor is used for the reverb recovery.
The M10 used a heavy duty 8" Oxford Alnico speaker with a 3" tweeter. The closed cabinet was divided horizontally, and the speaker chamber was bottom half. Jensen ceramic 8" speakers were used a bit in 1964 as well.
This fantastic example of an M10 along with its matching RS1 cabinet belong to Paul Wilczynski who also gets credit for the photo.
Like most of the Custom Series amps of this era, Estey engineers made running changes to the M10 as improvements were made to the circuit. This means the schematic in an amp might not exactly match the circuit in the amp.
Early M10's had a different first stage of amplification than the M10 schematic most commonly found (like the one on this site). The later M10, which might have appeared one to two months into production used a fixed bias for the 7025 with precision resistors setting the cathode voltage based on B+ voltage. The earliest M10s were self-biasing on this first stage. The reverb design is the same, but the earliest M10 examples had slightly different values for some of the components.
If you want more information about differences in these early M10's, please contact me.
The M10 was revamped in the spring of 1965, becoming the M10A.