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SERPs plus Sophia 6SN7 in residence at chez KevinF.

Sophia Electric Royal Princess 300B and 6SN7 Tubes Review

SERPs plus Sophia 6SN7 in residence at chez KevinF.

Click away now if you are of a sensitive disposition. This isn’t going to be pretty. It’s a story of the pursuit of audio perfection (so we know already it will end in tears), a story of decisiveness in adversity, of capitalism and market forces in the raw, of Western arrogance, of pension plans going to Hell on a handcart, and of why you should never play poker with a Chinaman. All it needs is a love scene and it could be set to music: Flash My Getter – an opera in three acts.


Last year I bought a quad of Psvane TII 300Bs to use in my Audio Note (UK) Kegon monoblocks. The Psvanes drove me to distraction with their loooooong burn-in, but once they’d settled I became a real fan, and I wrote in the conclusion of my review here on the ‘wam that I thought they were evidence that the Chinese were no longer simply copying Western technology, but were making advances they could rightly call their own. In my system and my room, to my ears, they were much nicer than a quad of 2004 Westrex 300Bs loaned to me my good pal Balcolm (he’s Malcolm really, but we call him Balcolm because he always seems to have a cold.) Anyway, Balcolm thought the Psvanes were better too and, kudos to him, promptly cut his losses and flogged the Westrex tubes to a collector, replacing them with TIIs.

I’d bought the Kegons, used. As the seller put them in the boot of my car, he predicted I’d eventually end up with vintage Western Electric 300Bs in them. The way they responded to better tubes would, he said, seduce me up the ladder of ever more costly 300Bs until there was ‘no further to go.’ As it happens, I’ve recently jumped a few steps, missing out the ‘we’re on our way’ and getting to the ‘no further to go’ with a loaned quad of vintage WEs from 1953. Generous Balcolm again, of course.

“Kev, just don’t bust them, OK?”

‘OK Balcolm. I’ll be careful.’

Oh my. I really do get what all the fuss surrounding vintage WEs is about. They are simply glorious. They made the Kegons sing like I’d not heard before. Human voice – glowing, utterly lovely. Acoustic instruments – glowing, utterly lovely. If I hadn’t recently heard European 300Bs from KR and more recently still Emission Labs I’d think vintage WEs incomparable. But the fact is that in the right amplifiers the Czech tubes get pretty close (as do the Psvane TIIs), but in a drier, leaner, more hi-fi kind of way. The Czechs do something with their 300Bs that make them sound rather un-300B-like: both factories produce tubes that have substantially tighter and deeper bass than the WEs and with more top end extension too. They don’t have that romantic fatness around the middle that WEs have, but for many people that’s not a shortcoming but a positive. Then there’s the European odd one out, JJ, whose 300B – now nicely made again after a period of shockingly poor quality – is the 300B for people who really prefer transistor amplification. The more I hear JJs the more I dislike them for their tipped up, etched presentation. They are so far from the WE benchmark, so dry and so unremittingly sand-like that, well….

It’s been said that in comparison with the Czechs the Chinese manufacturers produce 300Bs that are richer, sweeter, closer in sonics to the benchmark original. If we were unkind we might observe that this is because they’ve been ripping clones of WEs for so long now that they jolly well ought to have got it right by now.

Little and Large. Shuguang 300B left, SERP on the right.
Little and Large. Shuguang 300B left, SERP on the right.

In reality, until recently the Chinese have had more success making their 300Bs look like the original and less success making them sound like the original. It goes to show that reverse engineering doesn’t always succeed. Sometimes you just have to step up and do some R and D of your own.

Backed by injections of American and European capital, the Chinese are now doing some serious R and D. Some of what I learned during the interviews for my recent article on tube provenance here on the ‘wam leads me to the view that we are on the verge of a second golden age of tubes. China-driven, it will give audio designers and audiophiles a whole new and exciting set of options. Remember: you read it here on the ‘wam first.

The downside of this for those of us who’ve banked our pension hopes on a hoard of NOS tubes from the first golden age could well be disappointment. I can see values plummeting. Unless you are a collector, why, for example, would you pay in excess of $4,000 dollars for a pair of vintage WEs when modern production tubes costing a quarter or less of that perform not just equally well, but even better? Even so, and while we are on the subject of prices, allow me please to let out a howl of pain on behalf of audiophiles everywhere. Those of us with amps that use 300Bs are still being gouged, even if we choose to buy new production. Gouged. There is no other word for it, and it’s all the fault of the vintage WE. It’s capitalism red in tooth a claw, but the damned WE sets the price for the tube type, enabling manufacturers to make eye watering margins on new 300Bs. Take a Psvane TII 845 in one hand and the same manufacturer’s 300B TII in the other. No one is going to tell me that there isn’t more iron, glass and complexity in the 845, in fact much, much more – and yet the 845 costs fifteen quid less than the 300B.

Among the brands charging even more royally for their flavour of 300B is Sophia Electric whose flagship tube of that type – the rather quaintly and in the circumstances perhaps aptly named Royal Princess – costs around £900 a pair in the UK. Stiff though this is, it’s modest compared to the ‘Japanese’ (it’s actually Chinese designed and manufactured) Takatsuki – the latest wunderkind on the 300B tube block, priced at some £1800 a pair.

Ha! Call that a price? That’s a price!

The Sophia Electric Royal Princes (shortened to SERP hereafter) is manufactured for Sophia in Tianjin, northern China, by one of three producers that Sophia buys from. The factory originally made the All Music brand, but suffered a financial collapse in the late 90s due primarily to poor quality control. Sophia helped stand the factory back on its feet, went on to provide QC input and help with the development of a new range of tubes, and is the factory’s largest customer still, and by some considerable margin. The relationship has unfolded in a typically polite but opaque Chinese fashion, not in every respect in ways that Sophia Electric would have wanted. The principal thorn in Sophia’s side is that much of the production it rejects as being sub-standard is not crushed by the factory, but is sold to other brands. The availability of these cheaper tubes muddies the waters for Sophia, but here’s precious little that it can do. Read my earlier article for more on this subject.

The SERP, in comparison with many other Chinese 300Bs, is built like the proverbial battleship, weighing 130 grams against a standard Shuguang tube at just 86 grams. The SERP retains the classic ST glass shape, but at 15cm high from its base to top of bottle (excluding pins) is more than two centimetres taller than the Shuguang and fatter around the girth too. Some of the extra weight is due to thicker glass, but most must be down to the carbon coated plate which in plan view is a folded cruciform some three millimetres thick, and quite unlike the plate of a WE or its clones. The filament wires are also different, not hung from coil springs a-la many of the WE clones, but suspended through and above the top mica plate on spring cantilevers, rather in the way a fishing rod suspends a fishing line. The outside filaments can be seen through two holes in the adjacent vertical edge of the plate, but these are the only penetrations – the plate is otherwise solid. The getters are what look like stainless steel and are substantial and uniformly made and located. The flashing is deep and lustrous, extending evenly right around the base of each tube and some four centimetres up the side. The base of the SERP is ceramic, with gold plated pins.

Sophia has the factory cherry-pick the best by test from the production line. It then ships them to its facility in Virginia in the US where a Sophia technician tests, burns in, then tests again and matches the tubes. The work is carried out on a custom rig at both 300V and 350V, examining plate current, transconductance and residual distortion. It’s a belt-and-braces procedure, not only costly, but resulting in an uncomfortably high rejection rate that at times has meant a high percentage of tubes being sent back to the factory. Ever wondered why the look-alikes are so much cheaper? There’s your answer.

SERP suspended filaments.
SERP suspended filaments.

But why bother with such a palaver when most tube manufacturers simply bang out their production after a straight forward test of plate current? Sophia says that tubes can change significantly in electrical performance in the early stages of their existence and a pair that match at say five hours might not do so after 20 hours. The first measurement weeds out most of the tubes destined for the plane ride back to Tianjin. The long burn in and then the measuring of all three parameters again enables a subsequent and much smaller further cull of weaklings, followed by the pairing of the surviving candidates. Sophia says this not only gives confidence that the tubes will likely have a long life, but that they will deliver the best possible combination of even musical performance and sound staging. People will either ‘get’ the Sophia sound or not, but what they hear will be the optimum the design is capable of delivering.

And so we come to what I hear in my system. From the off, the SERPs were hugely weighty and quite dark with little top end. At approximately 20 hours they began the see-saw process that I noticed when running in the Psvanes last year. The major changes seem to occur not during listening sessions but between them when the tubes are rested. I’d light them up and hear something had happened during the interregnum – first a development of the bottom end, the next time a development of the top end, the next a smoother mid. Here’s an odd analogy, but it’s the best I can offer: imagine a chick hatching but unsure about which end of the shell to push against first. After some 100 hours I felt the SERPs had ceased to change much between sessions, so I sat down to listen.

My own driver tubes are NOS 5962s, but when I was talking with Sophia’s Richard Wugang for the previous article, he said that he thought I ought to try Sophia’s 6SN7s. More out of duty than in expectation of sonic fireworks I asked him to send me a pair. They arrived here after the SERPs had just about stabilised. Driven by the 5962s the SERPs sound similar to Balcolm’s vintage WEs but with at least an octave more of extension top and bottom. They’ve a little less of the bloom and luminosity about the middle, which I guess makes them more even-handed than the NOS benchmark, but they reach down and up in a way that just shows the dear old WE as being, as I said before, rather limited. As for inner detail, colour and organism, the SERPs are the equal of the WEs, able to convey subtleties in way that just makes me smile with satisfaction.

The Sophia 6SN7s are an unexpected riot. Dumpy ST glass, brass and ceramic base, and grey coloured plates make them look quite unlike any NOS 6SN7 that I have seen. They measure eight centimetres from base to top of bottle, again, excluding pins. Unlike the SERPs of which there is only one grade – the best – Sophia grades its 6SN7s into three bands, using a similar regime to that applied to the 300Bs. Grade A is the top, with grade B, Sophia says, the equivalent of JAN spec, and grade C being the lowliest – but still far better than those tubes being sent back to the factory. Evidence of the grading process can be found on the base of the 6SN7s in the form of marker pen lettering and numbering. The ones Sophia sent me were grade A, although they sounded anything but for the first few hours; quite rough and on the edge, particularly with vocals. But after about 40 hours they settled nicely.

Test serial number on base of Sophia 6SN7
Test serial number on base of Sophia 6SN7

Mr pension planner is not going to like this, but the Chinese 6SN7s shove his stash of RCA red base 5962s firmly into the sonic shade. Paired with the SERPs the Sophia 6SN7s are quiet; the level of background hum is less than other drivers I have used, and perhaps that helps towards the quite remarkable degree of air and delicate detail the combination delivers. The midrange is flatter and less fruity, and the bottom end is tighter and less blousy than the SERPs and 5962s can achieve. They sound both fast and slow at the same time, enabling music to flow with a real swagger when it needs to. Rim shots crack with power, and yet when notes should decay naturally the Sophia tubes allow them to do so, rather than truncating them through over-damping, or stretching them out with over-hang or after-ringing. A lightly struck cymbal, for example, faded away into the blackness, still shining as it gently died, in way that made me come over all wistful for my miss-spent youth as a percussionist in the school orchestra. Good audio can do that.

It is almost as if with the Sophia 6SN7s the SERPs morph into lush sounding 211s, so profound is the effect of combining the two tube types. I am always leery of quoting particular recordings in my reviews. You probably don’t share my lack of taste. However I have a bit of thing for Manu Katche at the moment. Running After Years opens with a wonderfully simple percussion figure that I never really *got* until I heard it with the Sophias. However, they reveal the intent behind Katche’s crafty timing, and show it to be a beautifully executed and textured musical event in itself. Good audio can do that too.

The Sophia tubes pull an amazing further trick in my system – they make my AN-Es image like never before. And yes, you there at the back. You can stop laughing.  I know that sounds improbable, but it’s true. I have never been a fan of the imaging artifice, valuing musicality and involvement way above anything else, so it’s startling to find that the Sophias make the wide-fronted Es behave like the narrow-fronted things they are not, throwing a sound-stage with much greater definition. Sophia says this is sonic evidence of the matching regime. Who’d have thought it?

There’s something too about the way the Sophia’s have made me appreciate even more the Audio Note Kegons. I did think they were rather good before, but the addition of the Sophias seems to have given their fundamentally excellent circuit design and materials choices even more room to show off. Would the same tubes deliver similar results in other amplifiers? I simply can’t say for sure, but it seems likely.


Verdict: Pricey, but recommended.

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