noun – a person who fights with the fists;
a boxer, usually a professional.
The Keystone Pugilist is a wonderfully overbuilt and enhanced version of the classic 5f1 circuit made famous by the Tweed Champ of the 1950s. It was intended to be a student amp and fortunately failed at the task miserably. The volume knob got turned up to revealed a glorious distortion tone and the 5f1 became part of rock music history. Eric Clapton, Keith Richards, Joe Walsh, Billy Gibbons and many others used this amp as a weapon in the studio. Of course their versions were slightly tweaked to take their tone over the top. When we designed the Pugilist we set out to incorporate a couple of the more popular modifications via switches. This allows the amp to be run with a stock configuration or you can flip a couple of switches and it becomes a box of rage. A treble bypass circuit keeps the amp from getting muddy at lower volume settings and lets you explore a whole new world of clean tones not possible with the original circuit. It does all this without affecting the iconic sound of an 5f1 run wide open.
The Keystone Pugilist is a single channel two input 5f1 utilizing a single 12ax7 feeding a single ended 6v6 power tube to produce about 5 watts of pure tone. The amp is powered by a 5y3 rectifier tube. Switches to enable/disable negative feedback and a cathode bypass boost are located on either side of the 12ax7 tube. They a located there to minimize wire length and keep the amp as quiet as possible. Turn the negative feedback on and the cathode bypass boost off and you have a sweet sounding little amp. Disable the negative feedback and engage the cathode bypass boost and the amp produces a wonderful raw anger through the stock 10” Weber Vintage speaker.
All of our amps feature a unique “flying lead” from the input jack to to v1. We use a point to point wiring scheme and coaxial shielded cable to link this most crucial area of the preamp. The result is an amplifier that minimizes noise with no adverse effect to overall volume.
Unlike most 5f1 amps, this amp behaves very well at lower volumes too thanks to the treble bleed circuit which allows some of the treble tones to be reintroduced after the volume is lowered. This keeps the amp sounding musical throughout the complete range of volumes and makes the amp useable when others will simply be much too loud or two muddied at lower volumes.
The Keystone Pugilist is all handmade and hand wired in our own shops. Attention to detail is our hallmark. We studied and source parts for years before releasing our first model to ensure the highest quality build with as many US manufactured parts as possible. The end result is an extremely reliable amplifier with minimal signal degradation and tone to die for.
Here is a partial list of what we have used to build this fine instrument.
- Chassis: We use only a US made mirror polished stainless steel chassis for all of our builds. This means that the shiny finish isn’t chrome. The actual steel of the chassis is buffed to perfection. No fear of peeling chrome when you hand this amp down to your grandchildren.
- Circuit Boards: We build our own circuit boards from raw G10 garolite board stock and US made double turrets. By building our own boards we can incorporate customer specific mods directly into the design of the amplifier while creating very solid electrical connections that will last a lifetime. This construction technique eliminates the electrical gremlins that can be present using more primitive build methods while making the amp extremely serviceable should you like to modify components in the future.
- Transformers: We use vintage spec US made paper wound transformers in our builds. This ensures vintage tone but with modern reliability. Our transformers are always over built and over spec’d to ensure long life and flawless performance. The stock output transformer on the Pugilist is an oversized 15w model (the amp runs between 5 to 9 watts). This makes it very robust and allows for the use of solid-state rectifiers as well as 6l6 tubes. 120/240 International power transformers as well as multi-tapped output transformers are available upon request.
- Speakers: The Pugilist uses a US made 10” Weber Vintage Alnico or Ceramic speaker. Tough call. Both speakers are excellent but the alnico is a little better and more compressed for overdriven tone while the ceramic is slightly better for sweet cleans. We will happily put any speaker you like into the build but these are our baseline choices.
- Coupler Capacitors: We use US made Jupiter tone capacitors that we have selected for their sweet musicality and round highs.
- Filter Capacitors: All electrolytic capacitors are Sprague Atoms for long life and consistent power handling.
- Tube Sockets: We use high quality ceramic tube sockets for the 9 pin and octal tube sockets. We find the positive fit and high heat resistance adds to the solid build and long life of our amplifiers.
- Tubes: The Pugilist ships with a Tungsol Reissue 6v6GT, Tungsol Reissue 12ax7 and JJ 5y3 tubes. We have tried many combinations and have found this to be a good starting point. Have a ball with NOS tubes with this one. Best part is it only takes one of each so you don’t need matched tubes. Any 12a?7 derivative will work in the preamp. Power tube selection will also have a significant effect on the tone.
- Cabinet: We hand build all of our cabinets from yellow pine with baltic birch baffles. We have tried many materials and find this combination provides the best cabinet resonance. Our joints are meticulously dovetailed and our finishing work is impeccable. It almost seems a shame to cover them when you see the craftsmanship of the joins. Another feature of the cabinets is the use of threaded inserts to hold the panels in place. This is our answer to the widely used wood screw method which will eventually fail after the panels have been removed several times. Machine screws and threaded inserts are a much more permanent solution.
- Wiring: Our amps are all hand wired using vintage style wire. Due to the small chassis size we wire our Pugilist chassis with standard cloth covered pushback. This wire insulates well and provides a rigid lead dress to keep the wires in proper position.
- Resistors: We use only carbon composite resistors in the signal path of our builds. While some will argue that this has no effect on vintage tone, we aren’t taking any chances. Metal Oxide resistors are used for high stress areas like cathode resistors and within the power section of the amp.
- Hardware: Switchcraft jacks are standard on all Pugilist models
- Handle: We have replaced many handles on vintage amps over the years. For this reason we use only heavy duty handles that can confidently carry this amp without even the slightest fear of failure. The cabinet will break before the handle quits.
- Finishing pieces: We take great pride in our amps and use the highest quality finishing hardware available. We pour our own badges and knobs for the Pugilist from molten pewter and each amp is protected by metal corner guards and beefy rubber feet.