I had been wanting to build a new 15 watt EL84 based amp design for sometime and one of my great customers John Bumgarner allowed me to do just that. The current crop of "modern" el84 based amps do not lend themselves to a lower gain "less rock & roll" vibe needed for blues or jazz so I set out to make this one a little different. The circuit is a unique design that couples the ability to separate sustain and gain with the two interactive volumes while allowing you to clip the preamp or keep it clean. I used an NOS 5U4 rectifier for Johns particular amp instead of the 5AR4 to give him more sag. The overall breakup of the amp is also easily tailored with speaker selection. A greenback/GB12/Private Jack will breakup right away allowing for some over the top crunch when driven hard and a G12H30/Governor/V30 will stay clean until 2/3rds up the volume. I think this sound clip below speaks for itself. The rythum track was slightly dirty and the lead was set for clean sustain and some drums were added. The Prototype/Ser # 001 was wrapped in Black Crocodile and shipped with an Eminence Legend GB-12. A few more pics follow the sound sample.
Rythum(moderate gain) and Lead (clean sustain)with drums added.
Bristol 15 Specifications
Power Output: 15 watts
Chassis: Laser punched 2 mm Aluminum
Circuit Board - Handwired G10 epoxy resin board, tinned brass eyelets
Capacitors: JJ Multisection can,Mallory 150, CDE silver Mica, Sprague 715 OD, Sangamo Electrolytics
Resistors: Carbon comp, metal film and metal oxide throughout
Sockets: Ceramic chassis mount
Potentiometers: Alpha
Switches: Carling
Jacks: Switchcraft
Output Tubes: 2- JJ EL84
Preamp Tubes: 3 - JJ ECC83/12AX7
Rectifier: NOS Westinghouse 5U4GB
Transformers: British
Controls: Volume, Bass, Treble, Master Volume
Cabinet: Dovetail Joined 12 Void FreeBirch Ply