Sophia Electric 91-01 300B Single Ended Output Transformers

Regular price: $699.99
Sale price: $499.99

This pair has minor cosmetic imperfection.

300B Single Ended Output Transformers: Sophia Electric vs. Audio Note

Sophia Electric in-house made #91-01 and #91-03 and #91-05 output transformers were designed by Dr. DWU and Richard Wugang and made by Sophia Electric in-house.

Price for 300B OPTs:

Option 1: $699.99 per matched pair of Sophia Electric 91-01 300B output transformers potted in steel case, 3K or 3.5K Primary, 0-4-8 ohm secondary.

Option 3: $899.99 per matched pair of Sophia Electric 91-03 300B output transformers potted in steel case, 3K or 3.5K Primary, 0-4-8 ohm secondary.

Option 5: $1499.99 per matched pair of Sophia Electric 91-05 300B output transformers potted in steel case, 3K or 3.5K Primary, 0-4-8 ohm secondary.
Primary 3K/3.5K, Secondary 0-8 ohm. 4 ohm is optional (free of charge). Other impedance (16 ohm, 11 ohm and 6 ohm) secondary output tap requires custom-making. Additional cost $150 for 91-01 model, $200 for 91-03 model or $275 91-05 model for each additional secondary tap.

91-01 300B OPTs are being used in Sophia Electric 91-01 single ended mono-block 300B amplifiers. Please see review below:

Positive Feedback Review: "...The Sophia Electric Model 91-01 300B mono amps are audiophile dream amps, they have great sonics top to bottom, bass articulation that is the best I've heard, and the SE 91-01 nails all of the nerdy audiophile things like soundstaging, imaging, sense of space, and transparency in such a beguiling way that even music lovers that don't give a rat's ass about audiophile-type sonics will appreciate its prowess.

I recommend these amps heartily, and I'd give them my normal 'two thumbs up' endorsement, but that just wouldn't capture what these Sophia Electric Model 91-01 300B mono amps are capable of, so I've invented a new rating, the 'two hard nipples up' recommendation, which is the highest award I've given out to date. ..." ––– Jeff Day

91-01 300B single ended OPTs are the vintage winding method (like vintage WE) for mid range magic with excellent bass and excellent high frequency. Much better than most Japanese, European and US output transformers in the market. Great for all 300B tube in single ended circuit for output 8-10 W. It is the output transformer choice for Sophia Electric 91-01 mono-block amplifiers.

91-03 300B single ended OPTs combine the best vintage sonic characters and superior (even better than 91-01) high frequency extension (great for 91 amps that use 310A or 6J7 family of driver tubes).

91-05 300B single ended OPTs are the OPT choice for Sophia Electric flagship model 91-05 300B amplifier. They are very exotic with great soundstage and 3D dimensions of space and time. Sound stage is way wider than the two-side walls and deeper than any other brands of OPT in our transformer collections. Ultra resolution without brightness, without sharpness, ultra fluid with first class dynamic and speed. It does everything right!!! Authentic vintage WE core.

These 300B OPTs are designed for 300B amplifier operating at 350V-400V plate to cathode(or 420-480V B+) output 8-10W for single ended power with excellent bass extension and airy highs, rather than small OPT from Tango, Tamura on the Sun Audio Amp for suitable for smaller triode tubes. Designed to replace the OPTs on these commercial amplifiers. Full bodied sound, a lot of weight and dynamic range in the sound.

User experiences on 91-05 OPTs:

"I have had my 91-05 OPTs installed in my mono block versions Thorsten Loesch's Legacy amplifiers for about six weeks averaging an hour or so of music a day. My initial reaction was surprise as to how much better my system sounded with the 91-05s in use.

I designed and built previous transformers in 2002 when I was working with a restricted budget. I used a high grade iron core with the same dimensions as the 91-05s and used multiple sections in the primary and secondary windings. They measured well and sounded good.

This year the ongoing upgrading of my diy turntable was beginning to show limitations elsewhere in my stereo system. A change to a better Maxon motor, and plinth changes showed up deficiencies in the bass and paper midrange in particular. It was time to consider the performance of my diy OPTs.

With my new transformers everything is much improved. Image width and depth is better with much improved location of instruments and voices. Cymbals now have a metallic quality where appropriate. Bass is deeper but initially seemed less strong however I now realise that the bass is much cleaner. Perhaps a reduction in harmonic distortion makes the bass seem less powerful. The mid range was always good but is now much more detailed and realistic.

Of course the huge change in the transparency of my power amplifiers now means changes elsewhere in the system are more apparent so there will be more to tweak in the future." -- Martin, Australia

"Thank you for the help with hooking up the 91-05 opts. They sound spectacular! Your sonic description is very accurate. Liquid, deep, wide and spacious. I'm very pleased." -- Ted from Washington State

User experiences on 91-01 OPTs:

"I have been auditioning these Sophia Electric 91-01 OPTs for a little more than a week and two words that constantly come to my mind are sweet and spacious. They do really have a "magical" tone inside a "timeless" space if you so want it to be. The sound is quite seductive with nice dynamics but never sounds harsh in any way. It's nice to have the tonal balance these OPTs have that takes away a little bit of the otherwise for some people too analytical and clinical sound of the 300B. I'm using a pair of 97db speakers and there is really a lot of pressure (dynamics) and body in the music, very detailed and well articulate for sure.

Thank you and I wish you luck with your company..." -- Sonny/Chris from Sweden

"When I purchased a pair of your Sophia Electric 9101 opts for my 2A3 amp back in March, I really didn't know what to expect. I have two other tube amps, a push pull and a SE. Being an avid stereo lover over the last thirty years, it has been my hobby to check out all the high end audio dealers regularly to keep up with the sound that I could never afford. The only downside to this hobby is going home to your own system and not be able to enjoy it for weeks until your ears readjust to your own system. When the highly recommended amp builder I chose called me to let me know that the 2A3 amp using Sophia Electric 9101 opts he had wired up for me was on its way and told me in his opinion it was a big step up quality and sound wise from the usual triode amps he builds using Hammond, MagnaQuest and Silk opts and that it was at least as good and maybe better than any he had heard using Hashimoto's opts, I wanted to get excited but knew better having been let down before! Well I am proud to say now that I have had time to go through most of my music collection I am still overwhelmed! I am hearing sounds and nuances that I have never heard on all of my old favorites. The clarity and definition in the music is amazing! It is so accurate and the sound stage is just like being there live. My modified Khorns have never sounded so amazing! I can't wait until I can replace my RCA 5Z3 rectifier with the Sophia 274 meshplate and then replace my vintage RCA 2A3's with the Sophia princess 2A3's. I am happy to say my new hobby is staying home and listening to my own stereo! THANKS So Much Sophia Electric!!!" -- T.H. from North West Okla Amplifier Manufacturer's review/feedback

Tube Audio Lab(TAL) in California has purchased many pairs of Sophia Electric 9103 OPTs. Here is the user experience found from TALwebsite: Sophia Electric output transformers: Core: vintage Western Electric core(from WE chokes) and modern core mix, Wires: US made OFC Natual fiber(cotton) made papers and non-magnet stainless steel screws Hermatically potted in a metal case.

Sound: excellent high end extension, seductive mids and good bass. Magical! at least in my amps.

Very close to real Western Electric sound.

Listening experience:

Sophia Electric OPTs do actually sound very nice. I mean VERY nice. I honestly can't tell if these are significantly better sounding than the Hashimotos, if at all, since I don't have an amp with Hashimoto OPTs to make the AB comparison. But I get the same goosebumps when I hear these Sophia Electric made WE-core OPTs as I did when I auditioned Paul's amps (Hashimotos OPTs, $800 per pair + $200 shipping from Japan). It's all there- excellent high end extension, seductive mids and good bass. Mostly importantly, they are very natural sounding and musical. I am spinning some Jazz records as I am typing this and I can't remember for how long the amp has been on. It's been playing music for hours, but I didn't notice it(time flying quickly) because the sound is so comfortable. Hope I remember to turn it off before going to bed! Will I recommend these for future builds? Sure. After all, shouldn't a WE91A deserve WE sounding OPTs?" -- TAL(Tube Audio lab)