Here is a detailed description of the SEP20:
Single ended amplifiers have a special place in people’s harts. What many people do not like is the single-digit wattage ratings. There is more to wattage than just how loud an amplifier can get. In fact, loudness is always secondary to performance. A good, wide bandwidth amplifier will produce a wide sound stage containing vertical, horizontal and forward dimensions. To effectively provide all three dimensions, it takes some power. Our SEP-25 provides 25 solid RMS watts per channel from 20-20,000hz simultaneously, not just at 1khz. I never measure my amplifiers at a single frequency because that is an artificial rating. Only wide bandwidth measurements are taken with real, high quality, well recorded music.
SEP stands for Single Ended Parallel. Even though there are two power tubes per channel, this has nothing remotely to do with push pull. The great thing about SEP technology is that we can increase the output power by adding as many tubes as necessary! Odd tube numbers work as well as even ones. We can make SEP’s up to 50 watts or more per channel. A SEP amplifier is derived from a standard single ended design. In the amplifier shown, each channel has two power tubes driven in parallel. In effect, it is the same as one single giant power tube. Clarity, the ability to sustain bass notes, midrange richness and high frequency purity are all increased many times over a standard single ended design. I am quite familiar with amplifiers using 845’s, 813’s, etc… They do sound good, but are exceptionally expensive if you want true high end representations. Our SEP-25 offers more power than most single tube, high end single ended amplifiers and will perform as well as or better than SE’s costing twice as much.
Development began around a set of James output transformers. These potted outputs are extremely high quality. Construction is impeccable and materials used are the finest grade. You will not find too many differences between these and vintage UTC brand outputs. To make this amplifier unique, I used a NOS Stancor power transformer with a solid copper EMI suppressor band. This transformer was never used. I pulled it right out of its original box. All the voltages it provides are ideal for this amp and it provides more filament current than necessary. It was being saved for something special, so it went into this new 2010 SEP flagship. All wiring is point to point with special double insulated tube amplifier wire that is cotton covered. Nothing finer can be used in a tube amplifier.
Our flagship SEP features a power supply that has our 1940’s upgrade. In the 1940’s, high grade tube power supplies were made to operate with heavy chokes and solid capacitors. The reason why we adopted these practices is because we noticed these units can remain functional for half a century and when made properly, are extremely quiet. Our 1940’s equipped amplifiers have heavy chokes as well as solid capacitor primary filters along with added filtration stages, numbering four total. We designed the rest of the amplifier to take advantage of this special power supply. The end result is a very low noise floor, increased amplifier efficiency and longer lasting tubes. Along with this upgrade, you will have the option to go between tube and solid state rectification with the flip of a switch.
Other features include tunable biasing and variable feedback. Tunable biasing is a DC biasing method that does not require a volt meter to use. Biasing is calibrated and marked during burn-in. There is leeway on either side of this mark so you can fine tune the tubes to your liking. The rule is this: Locate the position that sounds best and produces the least amount of heat from the power tubes. That’s all there is to it! Variable feedback insures a perfect interface between amplifier and speaker system. Adjust this control to your liking. When completely off, there is zero loop feedback.
The amplifier is finished with solid highly figured tiger ample on three sides that is completely hand made and utilizes dove tail joints on the front corners. We used crimson red pearl for the interior finish.
*James potted output transformers
*20 watts per channel into 4 and 8 ohm loads
*Frequency response: 20 to 20,000hz
*High current power supply with 1940's upgrade and additional filtering above that
*5AR4/5U4 tube rectification or solid state rectification with the flip of a switch
*6SN7 high resolution drive circuit6L6 and El34/6CA7 compatible power tube selection
*Tunable biasing: Perfectly bias the tubes without a volt meter, quickly and easily
*Variable feedback: Makes it possible to exactly match the amp to your speakers
*IEC power socket
*Dimensions: 17x10x8 inches @ 40lbs