1964 Magnatone 440

One of the most rare and interesting amps I’ve gotten to work on - This is the Magnatone 440, a medium powered amp (15-20 Watts) with all tube spring reverb and real pitch-bending vibrato. The amp is perfect for that late 50’s/early 60’S blues sound and even British Invasion stuff. It remains very firmly in that camp though sound-wise. It uses a very unique lineup of tubes 2 X 12AX7 (Preamp gain stage/Phase Inverter), 6EU7 (Reverb Recovery), 12AU7 (Vibrato Phase/Driver), 6DR7 (Vibrato Osc./Reverb Driver), 2 X 6V6GT (Power Tubes), and a 6CA4 (Rectifier).

Everything about the schematic design is unique - even the 12AX7 preamp stages are not like any other major brand. But the thing that is truly different is the pitch-bending vibrato - also known as frequency modulation (FM). It is really a type of phase shift modulator that uses an LFO to drive two Varistors (resistors that change their resistance value when voltage is applied) that essentially mix in anti-phase each side of a cathodyne phase inverter type circuit into the final signal. This amp was nearly all original and needed a full cap job (all electrolytics and many paper/oil caps), new upgraded wire-wound and metal oxide power dropping resistors, a nearly complete new lineup of tubes, and some wiring cleaned up and modified to be safer. The death cap was removed, everything cleaned and the amp was biased with a new 300ohm 10W resistor to Cathode Bias the 6V6GT’s at %92 Class AB Plate Dissipation. It originally came in with the wrong type of tubes in several positions, open filter caps, stress to the transformers, weak vibrato, and weak muddy tone. All of this was remedied and this piece is back from the dead.