The Keystone Quaker is our derivation of the classic 5e3 circuit made famous by the Fender Tweed Deluxe™ of the 1950s. We restored and studied amps from this era and used this knowledge to improve the reliability of our Quaker series without diminishing the mojo contained in this classic American amplifier. The 5e3 circuit has a wonderful range of clean and raunch tones provided by the two channel bright/normal interface. The four input jacks allow for high and low input signals on both channels and allow the player to jumper the two channels and play with the all the tonal possibilities of the interactive volume controls.
The Keystone Quaker is a two channel 5e3 circuit utilizing a 12ay7 to 12ax7 preamp to phase inverter. The power section is fed by a 5y3 rectifier into a dual 6v6 push/pull power stage. Since the design replaces the original ground switch with a standby, it is easily adaptable to a solid-state rectifier which provides slightly higher voltages and less sag. This is best done using a simple and inexpensive solid-state rectifier which fits directly into the 5y3 socket. No other adjustments are needed but for best power tube life it is recommended that you wait at least 45 seconds after turning on the power before you engage the standby switch. This will allow the heater element in the power tubes to get up to operating temperature before hitting the power tubes with current.
The Keystone Quaker 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 our own modifications such as flying shielded leads to via as well as 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. 120/240 International power transformers as well as multi-tapped output transformers are available upon request.
- Speakers: The Quaker Classic uses a US made 12” Weber Vintage Alnico speaker for a truly American sound. We also make a Quaker with a 15 watt UK made Celestion Blue. This speaker sounds HUGE! So huge in fact that we have modified the first coupler cap slightly to compensate for this blue 40oz alnico powered animal. We will happily put any speaker into your build but have found that this selection works extremely well by providing smooth, articulate cleans and the alnico drivers provide beautiful speaker compression at higher volumes.
- 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 Quaker ships with Tungsol Reissue 6v6GT, Tungsol Reissue 12ax7, Electro Harmonix 12ay7 and JJ 5y3 tubes. We have tried many combinations and have found this to be a good starting point. That said we spend many evenings rolling NOS tubes through our Quakers and have had great results with a wide variety of cool old tubes. (Editorial: Mark loves NOS Phillips 5751 in both v1 and v2)
- 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. There is some debate over the type of wire that should be used in hand built amps. Some argue for teflon coated while others insist on cloth coated insulation. With our Quaker amplifier we take no chances and use cloth covered, teflon insulated heavy gauge wire to ensure proper insulation and maintain rigid lead dress.
- 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.
- Potentiometers: The Quaker uses CTS pots for long life and reliability.
- Hardware: Switchcraft jacks and Carling switches are standard on all Quaker 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 Quaker from molten pewter and each amp is protected by metal corner guards and beefy rubber feet.