Introduction:
Way back in my college days, I used to own a Harman-Kardon Citation V amplifier, which was supposed to use 7581 output tubes. At the time those were rarer than GEC KT66s, so I ended up running RCA black-plate 6L6GCs which had the misfortune of being on the edge of their max dissipation. A red line would appear right along the plate seam, at the time making me nervous as hell. The only inexpensive tube that could take the heat was the newly introduced Sovtek 5881. It wasn't the best sounding tube but it certainly could take the abuse.
The 1970s era 6P3S-E - except for the shinier getter - looks exactly the Sovtek 5881, but the former has become a sort of budget audiophile darling while the latter is known as a rugged guitar tube. I was curious to see how the 6P3S-E would sound, and at roughly $24 shipped for a pair, I thought it was a perfect tube to try out in the Multi-Valve amplifier which had adjustable fixed bias - needed for dialing in a larger number of popular octal power valves.
Since I also have a pair of newer 5881s on hand, I also decided to compare the two. Physically they appear to be the same tube - rather business-like - but perhaps the cathode chemistry or even the plate metal quality is different enough to make a real world difference. Let's find out!
Note: 6P3S-Es were burned in for approximately fifty hours before listening. The Sovtek 5881s have been used for regulator service and for testing new amplifiers - hours are unknown but definitely more than a hundred.
Listening to the 6P3S-E:
Blue Nile - Hats is a rare vinyl treat with swooping synthesizers and melancholy lyrics. It isn't the most natural sounding album but has great dynamics and a dramatic soundstage. Through the 6P3S-E, there seemed to be a touch of iciness - perhaps an artifact of the recording - but I've heard more richness with other output tubes, notably many NOS units like the Mullard EL34 or the Tung Sol 6550. But still, the 63PS-E has a good transparency which will be loved by many modern music listeners who grew up with solid-state gear.
Next up was the half-speed master of Willie Nelson - Stardust. Detail was very good, though not the best I heard. It was the kind of fake detail caused by excessive treble. Once again I was reminded of a good, but slightly aggressive solid-state amplifier. Perhaps this tube would be a better match with some paper tweeters or a dull front end, but with a horn tweeter and a moving-coil cartridge the sound was rather forward. Bass depth and control, however, was quite good as was transparency. I wish I could combine the 6P3S-E with the darker sound of a Mullard XF2 EL34. That would give a more ideal tube.
I dug out my copy of Steely Dan - Pretzel Logic and gave it a spin. The treble energy didn't seem as hot on this album, but once again I heard a slight sterility to the sound. It wasn't bad - but the 6P3S-E seemed to falsely increase detail by cranking up the treble, adding some glassiness. The sound didn't really breathe at least not with the musicality I expect from the very best of the NOS tubes. I didn't get carried away with the music either, not even the soaring vocals of the song Barrytown.
Listening to the Sovtek 5881:
After some warmup I started with side two of The Grateful Dead - Terrapin Station, which is a very unique "rock opera" type piece. Once again the forward nature of this tube was evident. I'm thinking if I had an A/B switch box I wouldn't be able to tell the difference between this and the 6P3S-E. It had the same tipped up top-end, clean mids and good bass control.
In the right system, Cat Power - Jukebox has a big "you are there" sound. With the 5881, the effect was lessened, losing some of the inner-detail and the lowest, full bass. Again, it was good but the big DEPTH was shortened, making a flatter, less involving soundstage without the shimmer and swirl of the best output tubes. If there were differences between this and the 6P3S-E, they were incredibly minor. Just to be sure, it was time to return to a record I have already listened to.
Once again I gave Willie Nelson - Stardust a listen. Perhaps it was listener fatigue or system break-in, but I would swear the treble was actually tamer than the 6P3S-E. The mids were also a tad richer too. Both tubes, however, were still cut from the same sonic cloth - perhaps the difference between a Mullard XF2 and a XF3: different but not extremely so.
Conclusion:
The 63PS-E or Sovtek 5881 aren't bad tubes, but they aren't great tubes. They certainly aren't very neutral, hewing to a brighter sound than I like. They have a forward "in your face" sort of character that may be a better match for vintage speakers or certain MM cartridges. At least in my system, I wouldn't use them - not while I'm running compression driver/horn tweeters and a moving-coil cartridge. They are, however, recommended for budget audiophiles, but with serious system matching caveats. As always, YMMV.
Review System:
VPI Aries with JMW 10.5i tonearm and SDS Power Supply
Dynavector 10X5
Cardas Cross 1M interconnects
Quicksilver preamplifier with Mullard short-plate 12AX7s, RCA 12FQ7s, Amperex 12AU7
Cardas Quadlink 5C 1M interconnects
Multi-Valve Stereo amplifier
Cardas Hexlink speaker cable
UREI 813A monitor speakers
VTI BL503 equipment rack
