The not so often seen M14 was one of Magnatone's finest amps in 1964.
|Power||4x 7189A (two pairs for stereo)|
|Power Bias||fixed bias|
|Vibrato||2x 12AU7, 12DW7, 8 varistors|
|Phase Inverter||2x 12AU7|
|Speakers||2x 8" 16ohm|
|Output Trans||2x 10K:16ohm|
|Output||38 watts peak|
|List Price||$460 (1963-64)|
|List Price||$400 (1965)|
The Magnatone M14 was a premium, true stereo amplifier designed in 1963. Parent company Estey advertised the M14 as the "Club-Date Stereo Amp", and the "Mighty Midget", describing it in sales literature as the same as the M15 without Reverb. The M15 and M14 were the top of the line Magnatone amplifiers. While the M15 was a stout 65 lbs, the M14 was a much more managable 48 lbs, and ome 6" shorter. While the M15 shared the larger width and depth demensions of the M12 and M13, the M14 shared the smaller Royalite top of the M10 and M7.
The M14 was very expensive with a list price of $460 in 1964. Sales figures were low, as its chief competitor, Ampeg, was selling the Super Echo Twin for $380 and it came with two 12" speakers and reverb!
In 1965, when the rest of the Custom amps were treated to the silver motif change, the M14 remained in the catalog as the only gold trimmed amplifier. The price was also dropped to $400. Mostlikely, Estey had an overstock of gold M14 amps, so it stayed in the catalog until the last ones shipped. By late 1965, the M14 was dropped from the catalog.
The M14 and M15 are continuations of the magnificent 1961-1963 480. The only significant change to the circuit came with Magnatone's move toward 7189A power tubes and ultra-linear output transformers. The M14, like the 480 and the M15, is a true stereo amplifier. With twin 8" Oxford Alnico-5 14 ounce speakers, two output transformers, four 7189As, and two phase inverter 12AU7A tubes, the M14 had true stereo output channels (not just two input channels).
This amp can be confusing to talk about because there are two input channels and two output channels, but its not a single 1:1 relationship (like an Ampeg stereo amp, for example). Each input channel has its own pre-amp, and both of these signals are equally mixed together on both output sections. There is Stereo vibrato, but it only applies to the signal from Channel No.1 input. That signal is send to two different vibrato units, which each go to one of the two output sections.
The Stereo vibrato switch, in mono mode makes the two vibrato units modulate at the same frequency, and in "out of phase" frequencies in stereo mode. If vibrato was simply ON or OFF, the two vibratos, in stereo mode, might cancel each other out, however here in lies the magic. The Magnatone vibrato is the varistor. These magic varistors rise and fall at a much slow rate, so the rise and falls of the two output of phase vibratos never match up perfectly enough to cause complete cancellation.
The stereo vibrato is the same eight varistor design used in the 480. The vibrato was designed by Don L. Bonham and first applied it to the 280 in 1957. After Bonham's departure, Magnatone continued to use the design under patent license and called it Stereo F.M.Vibrato.
The first revision on the M14 schematic was released Aug.27, 1963. Between March and October of 1964, Magnatone began to use Jensen C8P speakers instead of Oxfords. During this time, Estey was going through bankruptcy and struggled to make payroll, let alone pay debts owed to suppliers. The switch from Oxford to Jensen speakers eventually became permanent for all Custom Series amps, but during the 1964 year, it seems they went back and forth with speaker suppliers.