http://www.providence.jp/providence_e/effect.html
Providence are a very serious pedal and cable manufacturer from Japan. They make impeccable stuff.
From their website:
"Background & Development:
The background of the SOV-2 begins with the original SOV-1. The SOV-1 used no vacuum tubes, but as a result of many years of development it successfully achieved the soft distortion and dynamics that are characteristics of the best tube amplifiers. The sound was good enough to satisfy respected guitarist Robben Ford, and two SOV-1 units were built especially for him. Robben also had a few suggestions as to how the unit could be improved, including modifications to the shape and layout of the knobs and switches that would prevent accidental changes to the settings in use, and a request for a smaller version that would be easier to carry. We also received numerous requests from users around the world for a smaller, lighter version that would run on batteries or an AC adapter.
In order to realize the requested modifications without compromising on sound quality it was necessary to reconsider the power supply. The original SOV-1 was AC powered and employed a precision power supply circuit of the type used in recording equipment. The sound of the original SOV-1 was to a large degree dependent on an exceptionally clean, stable power supply. It would be physically impossible to use the same power supply in a compact version, so a new circuit had to be developed from scratch. We decided to use a high-performance (and very expensive) DC-DC converter to deliver the ±15V power required by the original SOV-1 signal circuitry. A highly efficient filter was designed and implemented to prevent the converter's oscillator from interfering with the audio signal. The signal lines were also laid out with extreme care in order to optimize the unit's sound. What we have just described in a few sentences actually took several years to achieve, but the results in the SOV-2 are totally satisfying. A sample of the SOV-2 was sent to Robben Ford for evaluation, and he liked it so much that he ordered a second unit!
The SOV-2 is unique. It is an ideal match for Marshall, Fender, and a wide range of high-end and boutique guitar amplifiers. We sincerely hope that players will make it a part of their music: nothing could be more gratifying for a guitar effect designer."
Burgs. :)