I am not a clone builder. My amps are my own designs. While it’s fair to say nothing new has been invented since the RCA Handbook was published over 80 years ago, amp builders and circuit designers have been adding their own mark. Those of us today stand on the shoulders of giants like Leo Fender and Howard Dumble.
There’s a lot going on inside a Soul Tramp amplifier. There are features that impact the tone, some that contribute to durability and quality, others that are best practices for design and layout of components, and finally there is a love and pride from my hands in every amp I build.
My amps might well be the most complex hand-wired amps on the market. Building these amps would be far easier if I were to convert from turret boards to PCBs. But then I couldn’t look at each amp and smile at the time, care, and love I put into it. For me each amp is far more personal than just a product. Each amp is “old world” craftsmanship that I spend hours, days, weeks creating. It’s the difference between marble and stick-on vinyl tile.
All the information in this section does not capture the hours (50+) that I spend sitting at a bench fussing over every wire and component as I assemble each amp. It’s something money can’t buy; It’s passion and an unwillingness to compromise.
All my amps, other than the Tweed 12, have a unique tone-stack. I’ve added a “Slope” control which is unique to Soul Tramp amplifiers. This fourth tone-stack knob can be used to shift the mid-point frequency of the tone-stack. It essentially allows you to move the entire tone-stack to a higher or lower point within the overall bandwidth of the amp.
Reverb – Other than the Tweed 12, all the amps have tube driven spring reverb. Not much to say about this other than “if you know, you know”. Leo Fender nailed this a long time ago, and I don’t think anyone has improved up it. I have made a very minor change that I feel slightly improves articulation at higher gain levels. As well as a footswitch control, there is a bypass toggle to completely remove the reverb circuit from the signal path, and a Depth control to adjust the intensity of the reverb.
FX Loop – Again, other than the Tweed 12, all the amps have an extremely flexible tube buffered FX loop. Since not all pedals work well with traditional loops, there is a toggle to switch the loop between serial and parallel modes. There are Level and Mix controls to balance the wet and dry signals. As well, there is a bypass toggle to completely remove the FX loop from the signal path.
Rectification & Power Tube Bias – The Tweed 12 is tube rectified and cathode bias. It only makes sense for a “tweed” voiced amp to so the spongy sag of the power amp contributes to the bluesy distortion comes through. The other amps are diode rectified and fixed bias. This allows all of the voicing/tone to be created in the preamp. I feel this contributes to swirling harmonics and note separation. The probe jacks and bias pot are easily accessible.
Tube Heaters – The Tweed 12 has conventional tube heaters. All other amps have a mix of elevated A/C heaters and regulated D/C heaters. Regulated D/C heaters are as sophisticated as you can get, and typically used in high-end HIFI amps. It is more complex circuitry, more difficult to build, and requires special power transformer windings. The D/C heaters are used for the low gain preamp stages. It is here that hum from conventional A/C heaters can enter the signal path. All the other tubes use elevated A/C heaters which is a different (bit more complicated) method than is used in almost all other guitar amps. All of this is in an effort to lower the noise floor of the amp.
Chassis layout & Tube Locations – The tube locations on my amps my look haphazard/erratic, but they are located to so as to have minimal wire length between the tubes and associated circuits. As well each tube has a dedicated filter cap located next to the B+ plate supply. All of this is in an effort to reduce noise and stabilize the power supply.
Ground Schema – I use a floating star ground schema. It adds a layer of complexity to the layout design and is a bit more difficult to wire, but well worth it. It’s designed in such a way that chassis could be removed and the amp would still work (impossible to do for obvious reasons). This schema reduces eddy currents in the chassis that could introduce noise into the signal path, and allows the chassis to operate as an IMF shield.
Mercury Magnetics transformers – Need I say more?! I exclusively use MM transformers. There are typically three (power, output, reverb) on each amp. Before there was Soul Tramp, I spent years learning (thank you Tom, my mentor), and prototyping circuit designs. During this time, I tried all the brand name transformers. End the end, I settled on Mercury Magnetics. It was an easy decision. Open up a MM transformer and compare it to any other. The differences are readily apparent. As well, they are U.S. made. The ore that is used to make the iron cores comes from only one iron mine on the planet to insure consistency. To other transformer companies, iron is just a commodity to be bought on the open market. And finally, I require special transformer windings for my amps. This is a service they offer.
Weber speakers – Made in the U.S., these speakers are as good or better than any other stamped basket speaker on the market. Weber offers a huge selection of alnico and ferrite speakers with a mind-boggling variety of power and voicing options. Like most other musicians, I’ve played with lots of different speakers. When it comes to cast basket speakers, I still favor JBL and Altec, but there is little need for such speakers in these modern times.
Components – Each chassis is aluminum with reverse laser-etched front/rear panels. I only use Teflon wire and Beldon shielded cable. The resistors are either metal film or cement wire-wound. The capacitors are all quality pieces (TAD, Mallory, Sprague, etc.). G10/Fr4 1/8” glass/epoxy is used for the turret boards. I use ceramic tube sockets. Not for any good reason, I just like them better. The footswitch uses an XLR connector as it’s stronger than the typical connectors.
Printed Circuit Boards – There are two PCBs in my big amps. I designed both and have them manufactured in Canada. One is for the regulated DC power supply for the tube heaters, and the other is the relay board for the footswitch.
Fuses – The big amps have three fuses. One for the DC power supply (tube heaters), one for the B+ rail, and one for the A/C power from the plug.
A Little Bit About The Cabinets – I take great pride in my cabinets. For most amps, the cabinets are somewhat inconsequential, just something to hold it all together, and often made in cheap ways of cheap materials. It couldn’t be more different with my amps. They are made of ¾” half-blind dovetail joined pine, with birch plywood baffles. Where required, dowel pins are used for reinforcement. I spend hours building each cabinet. The tweed cabinets have 11 individual coats of shellac and lacquer to create a beautiful golden hue. Not to mention a smell that will make you smile and remember forever. I spent years prototyping cabinet designs that I was never quite happy with. Until “that” day. When I showed my wife the design that now identifies the Soul Tramp brand, she said “It’s beautiful, it looks like a Victoria Secret bra”. In that moment I know my efforts had paid off!
Amp Covers – The covers are also works of art. They are handmade by a craftsman who reupholsters hi-end cars and hotrods. Car seat vinyl on the outside and convertible top liner on the inside. The covers a beautiful!
