The Story of Enigma as told by our lead designer Ted Denney III

I began thinking about a tube based power supply for active shielding in the mid 90's while first developing Active Shielding Technology. At the time, I had an all tube-based system. and I mean ALL tube. I was listening to vinyl feeding an all tube pre-amp with valve rectification and an all tube power amp also with valve rectification. Like many audiophiles, I was tube rolling and amazed at the difference this made. One day a friend brought a box of his grandfather's old tubes to try. Sadly none were analog to the tubes I was using except for a handful of rectifiers. Initial disappointment turned to wonderment when we switched between rectifiers. At the time I had upgraded to Telefunkin and Mullard tubes and they were a significant improvement from the stock Russian and Chinese tubes I had been using. However when we plugged those old RCA rectifiers first into the pre amp, and then the power amp, the improvements eclipsed all tube experiments I had conducted to that date. I figured if a tube providing the DC to a pre and power amp could deliver such a profound impact on harmonic texture, sound staging, and overall musicality, perhaps valve rectification would offer similar benefits when powering Active Shielding. I filed this idea away for a future project that turned out to be a long time coming.

Fast-forward twelve years.
I had recently completed development of the Tesla Series interconnects and speaker cables and was looking for a new challenge. As fate would have it I was seeking someone who could develop my idea for a tube based power supply for Active Shielding. I figured if I could get a working prototype together for proof of concept, perhaps the benefits would be tube like smoothness and liquidity in my all solid state system without sacrificing what I love about my reference setup; namely its ultra black background, low frequency control, and precise imaging. I was actively seeking a designer for a valve power supply when a group of audiophiles and manufacturers arrived at Synergistic Research to experiment with a new PC based audio server. This is when I met Mikhail Rotenberg of Single Power Audio.

Mikhail and I got to talking and I mentioned my idea for valve based Active Shielding as I had done times before. The difference was in Mikhail's response. Previously when I shared this idea it was met with the usual "Oh that's just Ted and another one of his crazy ideas" or "why should that work-the DC is out-side the signal-path" Mikhail however was different as his eyes lit with instant enthusiasm. This spilled over into esoteric ideas pertaining to circuit design where we would inadvertently interrupt one another finishing the others thought. When we finally began discussing the details for a tube based Power Supply for Active Shielding, I expressed to Mikhail that it should have a Mercury Vapor rectifier and a Plytron Transformer from Canada at its heart. I knew from experiments and from listening to tube based amplifiers from Japan that only a Mercury Vapor rectifier would give me the sound I was looking for. No sooner did I express my desire for impossibly hard to find tubes and penchant for the expensive Canadian transformer did Mikhail disclose he had purchased the entire stock of rare NOS tubes from a stockpile near West Point Academy which was a depot for replacement tubes for the US Army dating back to WWI- including a large stock of NOS mercury vapor rectifiers. Amazingly Mikhail only uses Plytron Transformers in his higher end headphone amps-so far so good .

I then shared with Mikhail lessons learned from my first high performance power supplies for Active Shielding, The Master Control Center and later, the Quattro. Armed with this information Mikhail accepted the challenge.

From Prototype to Voicing to Produciton
As it turns out Mikhail is perhaps one of only a handful of engineers with the expertise to work with such tubes and is the only designer with a reliable supply of NOS tubes to make such a project a commercial reality. Over a six week period Mikhail and I spent hours discussing his progress; fine-tuning a working prototype that would allow us to listen to different tubes and circuit options. What ever thoughts I shared with Mikhail, they were merely guide lines based on intuition regarding what I felt would contribute to a high performance circuit. Mikhail on the other had had the knowledge and vision to turn my ideas into a working reality. When the final prototype arrived we were able to change everything from the amount of coupling capacitance (now the world's first component to employ my Patent Pending Active DC coupled capacitors) to different types of tubes, and even different transformers for the power supply.

Mikhail's foresight in providing a working test-bed from which to compare different circuit options made all the difference when voicing the final circuit. My hunch regarding tubes and transformers were confirmed, however my capacitance values for the coupling caps were way off. Further refinement through listening tests showed that using valves to power the interconnects and speaker cables is nothing short of a miracle but when powering the shielding on our power cords, this task is best left to a solid state diode due to a tighter control of low frequencies in this application. The shocker was the 1943 Western Electric and 1932 GE Tungar Thyratrons. We compared dozens of different tube options each with its own unique sound. However it was the Tungar and Western Electric that came shining through. In the end we decided to make a version with just the Western Electric and a special edition to employ both tubes so a lucky few can experience the magic of the ultra rare 1932 Tungar. The rest is history in the making as the world's first hybrid valve / solid-state 30 volt DC power supply; with interconnects, speaker cables, and digital cables being powered by one or two valve options and a solid-state option, with a separate solid-state power supply providing DC to the shields of Tesla power cords."

For more information on Single Power Audio visit their web site www.singlepoweraudio.com