When I reviewed the Sophia Electric Model 91-01 300B mono amplifiers for Positive Feedback Online back in January 2011 - which I purchased after the review - they came with NOS vintage Chinese JAN grade 5Z3PA rectifiers (which you can generally substitute for 5U4G and 274B rectifiers).

I am just now realizing how good these rectifiers are as I've been comparing them to other NOS and currently available rectifiers. I would like to say the vintage NOS RCAs are better, because that's often the word on the street, but that's just not the case, as the 5Z3PA pretty much slaughters it.

I should probably explain that last statement a little more. If your only measure of a vacuum tube is audiophile parameters like transparency, detail recovery, and the like, you might very well prefer the RCA.

However, on musically meaningful criteria like truth of timbre; portrayal of saturated tonal colors; the way melody, rhythm, and tempo, are portrayed; the humanness and expressiveness of voices, the 5Z3PA pretty much stomps the RCA. Now here's something to think about: the RCA is acknowledged as a great tube, and it is in fact a great tube, but from a musical standpoint I like the 5Z3PA alot better.

It also turns out that the vintage JAN 5Z3PA was used in critical aircraft applications back in the day, just as my FAA tubes were that I discussed in an earlier post, which means they are designed to work well even under difficult conditions, and to keep on working for a long time. It's been approximately two years since the Sophia Electric 91-01 mono amps were sent to me for review, and those 5Z3PA rectifiers are still going strong.

I like them so much I decided I want to run them in the Fi 300B mono amplifiers too, so I've been trying to find some to buy, with no success at all.

I checked the Sophia Electric website, and alas, they are not listed there either. However, I figured that if anybody would know where I might be able to find some it would be Richard Wugang, so I sent him a message asking for help finding some 5Z3PA. Somewhat to my surprise I got a nice - and very interesting message - back from Sue Wugang, Richard's wife:

Hi Jeff,

Glad to hear from you. Richard bought quite a big lot. If you can email over your shipping address, I can send you a pair.

Richard said these vintage 5Z3PA tubes were designed to compete and to replace RCA 5U4G during the cold war. During Chairman Mao’s time, making a low quality tube was an instant "crime of anti-revolutionary". So you can trust Mil Grade tubes from that period of time for reliability. Please note that this cold war military production is quite different from Several Chinese current productions which bear the similar name but not related.

For many years, the Chinese tubes were not known for performance nor sound, the extreme musicality of these 5z3PA was from Sophia’s special treatment on tubes – the similar treatment was placed on Sophia transformers and Sophia Electric Royal Princess 300B tubes.

If any of your readers is interested in getting a pair or two, please contact us at "[email protected]" ($40 per tube).

Best regards,

Sue

So here's the deal: if you've got a pair of Sophia Electric 91-01 300B mono amps, or a pair of Fi 300B mono amps, or any other amps that can accept a 5U4G rectifier, you've got to give these 5Z3PA rectifiers tubes a listen - I really think they're something special. Here's the cool part - they're only $40 each, which I think is a bargain for their level of musicality.

As you can tell, I'm pretty excited that I found out that I can get these vintage military grade 5Z3PA rectifiers from Richard & Sue at Sophia Electric, and I'd like to thank Sue for sending me a pair, that was a really nice and unexpected treat!

Before I forget: As I mentioned in my earlier post about rectifiers, Don Garber shipped the Fi 300B mono amplifiers to me with the Sophia Electric Globe Mesh Plate 300B vacuum tubes. Don has told me for years how much he likes the Sophia Electric tubes from Richard Wugang, and I enthusiastically agree - they are great tubes. The Sophia Electric Globe 300B tubes (tubes on the right in the photo below) are really nice sounding tubes. I like the Royal Princess 300B tubes ($1200 per pair) better than the Globes, but I really like the Globes too, maybe even better than the superb Princess 300B mesh plates. As an added bonus you can buy the Globe 300Bs starting at $285 a matched pair, which is a very fair price indeed for a pair of superb sounding designer 300B tubes.

I'm going to try to post some more detailed impressions on the differences between the Sophia Electric Globe Mesh Plate 300B, the Princess Mesh Plate 300B, and the Royal Princess 300B, in a future blog post.

Be sure to say "Hi!" to Richard and Sue at Sophia Electric for me if you talk with them, and let me offer up a very big "Thank-You!" to Richard & Sue for making such great vacuum tubes available for us Hi-Fi nuts.

Ok, that's it for now, it's time for dinner and a little music. Happy listening!