The feature review of the new Sophia Electric Aqua II 274B rectifier is now live at Positive Feedback HERE.

Enjoy! 

As is my custom, I like to give the readers of Jeff's Place a preview of upcoming articles for Positive Feedback, which in this case is the new Sophia Electric Aqua II 274B rectifier. 

The full feature article will be coming to Positive Feedback in the next week or two, so stay tuned for that. 

Enjoy! 

Sexy Blue Tubes - The New Sophia Electric Aqua II 274B Rectifier!

Greetings friends, I hope you are doing well!

In August of 2019 the Shuguang Electron Tube Factory was shut down in preparation for a move to a new location. By March 2020 the World Health Organization declared Covid-19 a worldwide pandemic, which would result in the shut down of most vacuum tube production still operating in China. Then came the Russian invasion of Ukraine in February of 2022, which resulted in Western sanctions, with Russia responding with export bans that included vacuum tubes.

With China and Russia being the major manufacturers of vacuum tubes in the world, and the smaller vacuum tube manufacturers in other countries facing serious supply chain issues, the guitar industry, the audio industry, and the musicians and hi-fi enthusiasts that support them, saw the availability of many vacuum tube types plummet. 

The whole vacuum tube supply situation was a real downer for us hi-fi enthusiasts. As I gazed at my cherished vacuum tube amplification collection I wondered what would become of them. Would I run out of vacuum tubes before the supply crisis was resolved? 

There’s now reasons for optimism in 2023, as we are seeing some new production vacuum tubes becoming available again, with more to come.

New Sexy Blue Tubes!

In June of 2023 Richard and Sue Wugang at Sophia Electric told me that their new Sophia Electric Aqua II 274B (above) and Classic II 300B (below) were now available, which was definitely a cause for celebration among hi-fi enthusiasts around the world. Hooray!  

The release of Richard and Sue’s new premium Sophia Electric Aqua II 274B rectifier and Classic II 300B vacuum tubes were originally planned to coincide with Sophia Electric’s 20 Year Anniversary in 2021, but production was delayed due to impacts from the Covid-19 pandemic, but are thankfully now available. 

274B Vacuum Tube Rectifiers

In vacuum tube amplifiers, rectifiers have the important role of converting wall AC voltage to the DC current that the other vacuum tubes in the amplifier’s circuit need. 

The rectifier, as the first tube in the circuit to ‘touch’ the electrical supply, has a large influence on the overall performance and sound quality of the amplifier. 

In the amplifiers that can utilize them, 274B rectifiers are by far my favorites due to their natural sounding tonal properties, vibrant musicality, excellent dynamics, and their spectacular sound-staging abilities. 

The original 274B rectifier tube was developed by the legendary Western Electric company in the USA. The Western Electric 274B was a filamentary full-wave rectifier with an octal base that delivered direct current from an alternating current source. 

In my review of the original Sophia Electric Aqua 274B in 2017 (Issue 93), I had asked Richard if he would tell us about his design of the Sophia Electric Aqua 274B rectifier tube, and how it compared to the original Western Electric 274B rectifier tube. 

I thought it would be instructive to revisit that history, and to conclude with Richard’s latest 274B design, the new Sophia Electric Aqua II 274B rectifier that is the subject of this article. 

"In 2001, Sophia Electric debuted the Princess 274B rigid plate rectifier to fill the gap left by the WE 274B.” (below)

"Our Princess 274B rigid plate rectifier tube is a true replica of the vintage Western Electric 274B rectifier tube. Many audiophile users have reported that it sounds better than the original vintage Western Electric 274B in the WE91 300B circuit, or in a modern 300B single-ended tube amplifier circuit, and at a fraction of the cost.”

"In 2002, Sophia Electric introduced a mesh plate 274B (above). As much as we love the mesh plate 274B tube, the requirement of low capacitance of 10 uF or lower at the first capacitor limited its potential use."

“We consider the Princess 274B mesh plate "the ultimate choice" for today's high-end tube pre-amplifiers and headphone amplifiers, as well as for small triode (2A3/45/PX4/71A/205D/101D) tube mono-block amplifiers.”

"However, all traditional 274B rectifier designs (Sophia or Western Electric) have the limitation that the first capacitor in the power supply after the rectifier tube must be miniscule. For vintage Western Electric 274B rectifier tubes it can be no bigger than 4 uF, and for the Sophia Electric rigid plate and mesh plate 274B's the limit is a slightly higher 8 uF.”  

“No matter how great those 274B tubes sound, this capacitor requirement limits 274B applications, just as it did for the original Western Electric 274B rectifier during the golden age of vintage vacuum tubes. Mainstream rectifier tubes like the 5U4 (America) and 5AR4 (Europe) permit up to 47 uF in the first capacitor position in a power supply, making them applicable to a wider variety of power supply designs."

"So why bother with a 274B rectifier? Back in the early 1930's Western Electric designed the WE91 cinema amplifiers that utilized the 300B tube in a single ended output circuit. The WE91 produced an output of 5.6W, which was enough to drive the cinema horn loudspeakers of the 1930's to volume levels adequate for cinema sound reproduction. 300B tubes require about 60V RMS of drive voltage to achieve their full output power of 5.6W.  To accomplish this, Western Electric chose the 310A, a pentode tube, for their driver choice.”

"The pentode driver tube was an elegant choice, but it was at the expense of high frequency extension. Back then, 10 KHz was considered the maximum high-frequency for high-fidelity, with movie dialog being more in the mid-range.  Even so, Western Electric still wished for a little more high-frequency extension in their WE91 300B amplifier to make the sound more open and lively.  This demand called for a premium long plate rectifier tube, now known as the WE 274B tube.”

"Without the 274B rectifier tubes, Western Electric tube amplifiers sounded rather dark and dull. But with the 274B, Western Electric amplifiers sounded full and complete, and were a significant sonic upgrade.”

"However, when the power supply capacitor is higher than 8 uF the long plate of the WE274B sparks, which forced Western Electric to limit the design requirement to 4 uF.  This limitation prevented the 274B rectifier tubes from being used in a wide variety of applications, both in vintage times and today, as most modern equipment was designed with up to 47 uF capacitors as the first capacitor in the power supply so they could utilize 5U4G and 5AR4 rectifiers.”

“In 2016 Sophia Electric solved this limitation of the 274B in our Aqua 274B rectifier tube (above). Initially we tried to solve this limitation by using exotic materials, as in the design of our very popular Royal Princess 300B tubes, which utilizes platinum and rare earth materials.  We were successful, but the finished product was way too expensive for the average consumer to be viable.”

"Then we went back to the WE 274B structure design as a starting point, and in an unexpected way we figured out a way to solve the Western Electric limitation of 4uF. This solution allowed us to build the Sophia Electric Aqua 274B, which can use up to a 47 uF filter capacitor value, the same maximum value permitted for 5U4 and 5AR4 rectifiers.”

"In a 300B mono-block amplifier, such as Sophia Electric's 91-01, or the newer 91-01 Signature amplifier, the Aqua 274B can easily replace the 5U4 rectifier tube and deliver a wider and deeper soundstage, and deliver the musical magic that is otherwise missing when not using a 274B rectifier.”

"The blue tint that we've added to the glass not only looks exotic, but during the voicing process we found that the blue tint of the ST shaped enclosure added more sonic impact to the presentation of the music.” 

“Vintage US military tubes often had a black metal base and/or black-grayish smoky carbon-containing paint sprayed on the inside of the glass tubes for light shielding to reduce noise. British and German military tubes often used red paint for light shielding to reduce noise.  We have auditioned various light shielding possibilities, and ultimately settled on the blue tinted glass, which when combined with ST bottle shape, provided additional musicality and a distinctly better tone.”

"Back when all vacuum tubes were placed inside a chassis, there was no need for consideration about light induced noise. However, high-performance audio enthusiasts now like to see the tubes displayed in the open, so they can see them from their listening seats, and they also enjoy seeing the glow of the filaments.” 

“The blue tint ST bottle shape is an ideal solution, as it is a beautiful and excellent sounding bottle shape, and the blue tint offers the benefit of a reduction in light induced noise, while still allowing the listener to see the beautiful glow of the filaments."

The New Sophia Electric Aqua II 274B Rectifier ($250 USD)

Visibly the new Aqua II 274B (below left) version looks quite a lot different from the original Aqua 274B (below right). 

The Aqua II glass bulb has a somewhat different shape from the original Aqua, and the glass tint is a much deeper blue color. 

Here’s a summary of the new design features that Richard told me he incorporated into the new Aqua II 274B rectifier:

• The Aqua II has a higher current output (max 220 mA) compared to the original Aqua 274B (max 180 mA), and way more compared to the WE 274B (max 150 mA).
• The Aqua II has a lower impedance than any other 274B ever made, thus higher efficiency in converting AC into DC.
• The Aqua II has a higher dissipation power rating with visibly bigger and heavier internal construction.
• Aqua II has a new generation of spark arc suppression technology to eliminate arc possibility (WE274B is the internal spark arc king). 

Here’s how Richard says those design features affected the sound quality of the new Aqua II 274B:

"First, we describe it as far more musical than any other 274B or 5U4G tubes ever made. It has a higher resolution – akin to watching 8K video instead of 1080 – and even more live-performance-like sound. Every musical instrument and voicing are more clear-cut from the rest of the orchestra." 

"The Aqua II gives you the feeling that you've just upgraded your amp / preamp with a boatload of Black Gate capacitors. With Aqua II 274B the type of performance improvement one desires from Black Gate capacitor upgrade is fulfilled.”

"This MK II version of Aqua 274B tube is the ultimate 274B from Sophia Electric. It delivers an unforgettable magical sound that is the trademark of Sophia Electric vacuum tube house sound.”

While Richard didn’t mention it specifically, I am wondering if the much darker blue tint of the glass in the Aqua II 274B results in further noise reduction compared to the Aqua 274B. I would think so.

Audio System For This Review

For this article I used my Tannoy Westminster Royal SE loudspeakers that have been hot-rodded with an internal rewire using vintage Western Electric WE16GA tinned-copper wire, and custom external Duelund crossovers that utilize pure silver Duelund CAST components in the high-frequency / midrange circuit, and Duelund CAST pure copper components for the rest, with Duelund DCA16GA tinned-copper wire connecting everything together within the crossover.

The Triode Lab 45 EVO single-ended-triode (SET) integrated amplifier (below) was connected directly to the external Duelund crossovers with Duelund DCA16GA tinned-copper loudspeaker cables.

The 45 EVO was placed upon an Acoustic Revive RAF-48 Air Floating Board air isolation platform. 

The Audio Note (UK) CD 5.1x Red Book CD player was connected to the Triode Lab 45 EVO SET amp with custom Belden 8402 microphone cable interconnects terminated with XLR connectors on the source end, and RCAs on the 45 EVO end, respectively, that were provided courtesy of the cool guys at Best-Tronics Pro Audio. 

My wall AC outlets consist of Acoustic Revive CB-1DB receptacle base plates, CFRP-1F carbon fiber outlet plates, and custom Acoustic Revive modified Oyaide R-1 receptacles. 

AC from the outlet to the Acoustic Revive RPT-6 Absolute NCF Power Distributor was via an Acoustic Revive Absolute power cable, and power cables to components were a mix of Acoustic Revive Power Reference TripleC NCF AC power cables (amplification components), and Acoustic Revive Absolute power cables (source components).

Now let’s do a little listening. 

Listening Impressions

Ok, that's it for now. 

As always, thanks for stopping by, and may the tone be with you!