L-PA675 Pro — A 6L6 based 60W Fender Pro-Like PA Conversion

The above amplifier was originally a Lafayette PA675A PA Amplifier, 75W with EL34s. It had seen at least one attempt by someone to convert it to guitar amplifier use, and had been mangled and rewired and basically ruined with overheated solder joints and broken wires. Most of the components were of sufficient age to also warrant a complete rebuild.

I completely gutted the chassis, replaced the sockets that needed it, and completely rebuilt the amplifier based upon a 6L6 based Fender Pro style design, with a few twists. One twist is, I retained the 580V main power supply in the unit, pushing these 6L6s to 60W, and retained the secondary 300V supply for the preamp. And the rebuild utilizes the full point-to-point terminal strip to socket wiring techniques like the original vintage PA Amplifier.

The Preamp consists of a two stage front-end a standard Fender-style phase-inverter, and a tone-stack with the frequency breakpoints shifted to accomodate the awesome oversized (Hi-Fi style) output transformer in this unit (typical of PA Amps in general). The result is as applicable to use for a Bass as for a Guitar.

I have also added my Contour feedback adaptation control in this unit to allow a tight Fender clean tone or a more aggressive overdriven tone.

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