1968 Newcomb Pathfinder E-20

This is a 1968 Newcomb Pathfinder E-20 that I modded/converted to work better for guitar input impedance and frequency range. The Newcomb E-20 started it's life as a PA for the local school system and was originally designed for microphones and turntables.

This is an incredible sounding vintage amplifier that boasts an all tube signal path that is completely hand wired point-to-point with no circuit boards of any kind. It goes from a clean chime at lower settings, to an unbelievable British sounding overdrive at half volume, which then turns into a full on distortion/fuzz meltdown when cranked to 3/4 volume and above. Overall this amp reminds me of early Vox AC-15/AC30's that contained the highly sought after EF-86 tube pentode in the front end.

The power-amp puts out a full 24 watts provided by 2 cathode biased Mullard EL-84's in push-pull. The preamp section consists of a Mullard 12AX7 as the input stage and a fairly rare RCA 6BR8A that contains both a pentode line driver and a triode phase splitter in the same glass envelope. The tube compliment is rounded out by a GE 5Y3 tube rectifier. The Cathode Bias was set to a slightly hot %103 Class AB Plate Dissipation with a B+ of 369VDC. All tubes are NOS and are original to the amp.

All the electrolytic caps are new (CE cap can), all signal caps have been replaced with Mallory 150 film type, power resistors have been upgraded to 2 watt metal oxide and 1 watt carbon film, and all potential problematic carbon comp resistors have been replaced with modern 1/2watt carbon film type. A Trainwreck style Type-3 Master volume was put in to replace the “Phono” knob/pot, “Mike 2” was made into a “Bright” channel and the pentode line driver was cathode bypassed with 50uf 100v electrolytic capacitor to give fuller frequency response. A speaker jack was also added for convenience. Much of the rest of the circuit design was left intact as it sounded great as is. This gem is ready to go for the next 50 years.