Dragging-up an old thread ‘cause found pair of 6Pi3S
Continuing my weeks-long shop cleanup, I happened across a pair of 6P3S.
Must have been purchased MORE than decade ago.
The manufacture date is July 1968.
Changed-out the cathode resistors in the shop SSE (additional sockets are for 6AV5 sweep tubes) and fired it up.
~393 B+
29.5 Vk over 344 ohms = 85mA
Assume about 385 Vp * 85mA = 32.7W dissipation
Wow, pretty darned good. Amongst my favs in the 6L6 extended family. Tempted to try them in a guitar amp, which is probably what I bought them for...
Question (this being the TubeLab Forum and all): has anybody discovered the dissipation limits for these puppies?
They’re acting like they would like some more juice. Practically begging to be turned-up to 11.
I see reports of 40 W on the International WW Interweb machine, but rumours only, no details...
Continuing my weeks-long shop cleanup, I happened across a pair of 6P3S.
Must have been purchased MORE than decade ago.
The manufacture date is July 1968.
Changed-out the cathode resistors in the shop SSE (additional sockets are for 6AV5 sweep tubes) and fired it up.
~393 B+
29.5 Vk over 344 ohms = 85mA
Assume about 385 Vp * 85mA = 32.7W dissipation
Wow, pretty darned good. Amongst my favs in the 6L6 extended family. Tempted to try them in a guitar amp, which is probably what I bought them for...
Question (this being the TubeLab Forum and all): has anybody discovered the dissipation limits for these puppies?
They’re acting like they would like some more juice. Practically begging to be turned-up to 11.
I see reports of 40 W on the International WW Interweb machine, but rumours only, no details...
Attachments
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In the spirit of TubeLab: Whatever the dissipation limit is, I went PAST IT...
After a couple of hours of that Rock and Roll Music, I happened to look BEHIND the back 6P3C and saw THIS; mind you, only one tube was showing signs of distress, but Red Plates do NOT a 6L6GC make, let alone a 6550.
But geez, they sure sounded pretty good. Will rebias below 30W tomorrow and see if the second tube will make it...
There's conflicting "information" on the web about these tubes:
(a) there are at least two versions: 6P3S and 6P3S-E or maybe -EV.
I am lead to believe that the -E is a military spec tube with ruggedized bits, but don't know if the dissipation is higher, lower or the same.
(b) there are at least three base styles: Black "coin" base, black deep base, and reddish brown deep base. Don't know if there's any correlation between max dissipation and base style; in USA tubes, the coin base version is often lower power.
(c) for vintage tubes, there appear to be at least two, probably three manufacturing plants. The ones I have are marked with the Reflektor Diamond.
Unless somebody has some helpful guidance, it appears the best approach is to buy a handful of the bargain ones, gradually increase the dissipation, then back-off at Embarrassing Redness. Hopefully quicker the next time. I might just see if my fave Russkie tube dealer in Ukraine has a deal on these, and what versions are available.
After a couple of hours of that Rock and Roll Music, I happened to look BEHIND the back 6P3C and saw THIS; mind you, only one tube was showing signs of distress, but Red Plates do NOT a 6L6GC make, let alone a 6550.
But geez, they sure sounded pretty good. Will rebias below 30W tomorrow and see if the second tube will make it...
There's conflicting "information" on the web about these tubes:
(a) there are at least two versions: 6P3S and 6P3S-E or maybe -EV.
I am lead to believe that the -E is a military spec tube with ruggedized bits, but don't know if the dissipation is higher, lower or the same.
(b) there are at least three base styles: Black "coin" base, black deep base, and reddish brown deep base. Don't know if there's any correlation between max dissipation and base style; in USA tubes, the coin base version is often lower power.
(c) for vintage tubes, there appear to be at least two, probably three manufacturing plants. The ones I have are marked with the Reflektor Diamond.
Unless somebody has some helpful guidance, it appears the best approach is to buy a handful of the bargain ones, gradually increase the dissipation, then back-off at Embarrassing Redness. Hopefully quicker the next time. I might just see if my fave Russkie tube dealer in Ukraine has a deal on these, and what versions are available.
Attachments
Re-Calculationn, Re-Baising, and Comparison w/ 5881 Red Base
EDIT!
Arithmetic should be 393-29.5= 363.5 Vp
363.5vdc * 85mA = 30.9 W
Still too high.
I re-biased with 466ohm Rk, which brought dissipation down to 25.5W and 27W. No embarrassing redness yet.
(1) clearly NOT a "matched pair", although I suspect they were VERY cheap, so not surprising
(2) Suggest this tube (Reflektor deep base 6P3S) should be treated like a 5881 (26W max triode dissipation)
(3)Note that my shop amp has B+ about 400-410vdc depending on load; this yields Vp close to to the max for a 5881. but in my experience that's GOOD.
(4) Nevertheless, the sound is particularly good. If you can get them CHEAP, they seem like a good substitute for new-build or NOS USA 5881 in the SSE.
I have a nice (but well used) pair of RCA 5881 Red Base. I popped those in there at same bias points to compare. The RCA were pretty well matched at 24.4 and 24.6W dissipation. For Ultra-linear operation, I figure you can split the difference between pentode max dissipation (23W) and triode max dissipation (26W) = roughly 24.5W, so we're about perfect.
The 6P3S DO compare pretty favorably to this old set of 5881s, although the RCAs are of course smoother, more "lush", more "detailed" (all those audiophile phrases)than the Reflektors.
Which brings up a perennial issue: should you buy well used USA tubes or new Russian/Chinese copies for about the same price? For hi-fi, I think I would lean towards building a cheap stock of USED USA tubes; they're just better, and folks are so focused on NOS tubes that they've lost track of how much life is left in a lot of those old USA tubes... so they're usually pretty cheap.
Guitar players: you're gonna beat the crap out of your tubes anyway, so buy a bunch of the 6P3S and bias down around 25 or 26W. They won't last, but they'll probably sound terrific.
EDIT!
Arithmetic should be 393-29.5= 363.5 Vp
363.5vdc * 85mA = 30.9 W
Still too high.
I re-biased with 466ohm Rk, which brought dissipation down to 25.5W and 27W. No embarrassing redness yet.
(1) clearly NOT a "matched pair", although I suspect they were VERY cheap, so not surprising
(2) Suggest this tube (Reflektor deep base 6P3S) should be treated like a 5881 (26W max triode dissipation)
(3)Note that my shop amp has B+ about 400-410vdc depending on load; this yields Vp close to to the max for a 5881. but in my experience that's GOOD.
(4) Nevertheless, the sound is particularly good. If you can get them CHEAP, they seem like a good substitute for new-build or NOS USA 5881 in the SSE.
I have a nice (but well used) pair of RCA 5881 Red Base. I popped those in there at same bias points to compare. The RCA were pretty well matched at 24.4 and 24.6W dissipation. For Ultra-linear operation, I figure you can split the difference between pentode max dissipation (23W) and triode max dissipation (26W) = roughly 24.5W, so we're about perfect.
The 6P3S DO compare pretty favorably to this old set of 5881s, although the RCAs are of course smoother, more "lush", more "detailed" (all those audiophile phrases)than the Reflektors.
Which brings up a perennial issue: should you buy well used USA tubes or new Russian/Chinese copies for about the same price? For hi-fi, I think I would lean towards building a cheap stock of USED USA tubes; they're just better, and folks are so focused on NOS tubes that they've lost track of how much life is left in a lot of those old USA tubes... so they're usually pretty cheap.
Guitar players: you're gonna beat the crap out of your tubes anyway, so buy a bunch of the 6P3S and bias down around 25 or 26W. They won't last, but they'll probably sound terrific.
Attachments
Sorry to say it, but this isn't a new discovery. These (esp. the 6P3S-E) have been sold as a 5881/6L6 replacement for a long time. Even re-badged by Sovtek as a "5881/6L6WGC".
Verstarkerrohren und AMP-Zubehor | Tube Amp Doctor.
The E version is much better regarded than the non-E.
They are, indeed, a hell of a bargain and sound great in the SSE (but don't pay double or more for the re-badged Sovteks). Around 19W they will last forever and still sound great.
Verstarkerrohren und AMP-Zubehor | Tube Amp Doctor.
The E version is much better regarded than the non-E.
They are, indeed, a hell of a bargain and sound great in the SSE (but don't pay double or more for the re-badged Sovteks). Around 19W they will last forever and still sound great.
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Clearly not a new discovery; they've been in the 6L6 box in my shop since ~2008.
The question was the upper limit of the dissipation, ala TubeLab.
This IS the TubeLab forum after all, where we "blow things up so you don't have to."
Has somebody else tried the upper limits of 6P3S dissipation? I couldn't find it....
Sounding "great" is of course subjective; they do sound surprisingly good, but I am not convinced they are even close to the better 5881s like the RCA Red Bases I have playing now. If the same price, take the used USA 5881s, at least for hifi.
IIRC the "E" designation means "ruggedized" for mil applications (like the Joint Army Navy JAN appellation for US tubes) which presumably means a better support structure (rods, insulators, etc) but I believe the thermionic bits are identical. Correct me if I'm wrong & I'll get some E's to Red Plate.
BTW, as usual, the 6P3s sound GREAT (as good as the RedBase 5881) when Red Plated, but they were already starting the death-knell "fizzle". Tant pis. (I speak a little Canadian, eh?)
The question was the upper limit of the dissipation, ala TubeLab.
This IS the TubeLab forum after all, where we "blow things up so you don't have to."
Has somebody else tried the upper limits of 6P3S dissipation? I couldn't find it....
Sounding "great" is of course subjective; they do sound surprisingly good, but I am not convinced they are even close to the better 5881s like the RCA Red Bases I have playing now. If the same price, take the used USA 5881s, at least for hifi.
IIRC the "E" designation means "ruggedized" for mil applications (like the Joint Army Navy JAN appellation for US tubes) which presumably means a better support structure (rods, insulators, etc) but I believe the thermionic bits are identical. Correct me if I'm wrong & I'll get some E's to Red Plate.
BTW, as usual, the 6P3s sound GREAT (as good as the RedBase 5881) when Red Plated, but they were already starting the death-knell "fizzle". Tant pis. (I speak a little Canadian, eh?)
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Just checked the FleaBay.
Very few good used 5881s or 6L6WGBs, and the good ones seem to be going for $15-25 per tube. Yikes. Like everything else thermionic, inflation has hit hard...
At these prices, cheap 6p3Ss sure do seem like a bargain. Just be sure to get a matched set, or buy a bunch and pick two, or bias them individually...
OTOH I am blasting Lionel Hampton thru the RCA Red Bases out into the street...better, rounder sound than the re-capped Quad 303, which is my reference amp for "cleanliness", so there's that... MAN those vibe bars are right in the room...
Very few good used 5881s or 6L6WGBs, and the good ones seem to be going for $15-25 per tube. Yikes. Like everything else thermionic, inflation has hit hard...
At these prices, cheap 6p3Ss sure do seem like a bargain. Just be sure to get a matched set, or buy a bunch and pick two, or bias them individually...
OTOH I am blasting Lionel Hampton thru the RCA Red Bases out into the street...better, rounder sound than the re-capped Quad 303, which is my reference amp for "cleanliness", so there's that... MAN those vibe bars are right in the room...
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These are not high power tubes.
The Soviet 6P3S is about a twenty watt tube.
The fat bottle -E is good for a few more watts. Sovtek originally sold them as 6L6GB before they went with 5881/6L6WGC.
About half of the vanilla 6P3S I've had were gassy. The other half does indeed sound good.
edit: If you want a 6P3S that you can beat the ever loving snot out of ... look for the old Shuguang 6L6GC in the small coke bottle bulb. I think they were sold as being nearly indestructible. I have some that have blackened on the top of the bulb - still work great ...
The Soviet 6P3S is about a twenty watt tube.
The fat bottle -E is good for a few more watts. Sovtek originally sold them as 6L6GB before they went with 5881/6L6WGC.
About half of the vanilla 6P3S I've had were gassy. The other half does indeed sound good.
edit: If you want a 6P3S that you can beat the ever loving snot out of ... look for the old Shuguang 6L6GC in the small coke bottle bulb. I think they were sold as being nearly indestructible. I have some that have blackened on the top of the bulb - still work great ...
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The 5932 is another 5881 / 6L6WGB type with a big fat base. Sometimes expensive, sometimes dirt cheap.
They come in an least two styles - those that look like a 5881 with a fat micanol base, and those that look to have two tubes paralleled in the bottle, also with a big fat micanol base.
No matter what brand is on the 5932, they are likely a Sylvania made tube.
They come in an least two styles - those that look like a 5881 with a fat micanol base, and those that look to have two tubes paralleled in the bottle, also with a big fat micanol base.
No matter what brand is on the 5932, they are likely a Sylvania made tube.
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Again, not trying to make 6P3Ss into something they aren't, just wanted to see what the upper limits actually were...
Your experience with gassy tubes matches my tiny sample; 1 of 2 tubes was excellent. That's not a very good yield when it effectively doubles the price of usable tubes.
I have some of those coke-bottle Shuguang 6L6GCs, and use them as Pass Tubes in regulated power supplies precisely because they're so rugged (plus the USA 6L6GCs originally in there were being wasted.) Unlike George, I didn't SELL them, but might NOW...
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"If the same price"
Well, if I could get a pair of NOS USA 5881 for $25 USD I sure wouldn't be buying the 6P3S-E tubes!
My point is that you don't NEED NOS USA tubes. Used ones that test strong can be a bargain. $15-$25 for good used ones is 3-5 times what I was paying 10 years ago, but probably still a bargain. Plus, if W5JAG's experience is typical (it was for me), then random NOS 6P3Ss have a "yield" around 50%, so factor accordingly.
Mine did sound pretty good though, just not RCA from Nuevo Jersey.
"If the same price"
Well, if I could get a pair of NOS USA 5881 for $25 USD I sure wouldn't be buying the 6P3S-E tubes!
I have a few NOS 6L6 in multiple variants. These are old, original boxed tubes. There are several Sylvanias from different periods, as evidenced by the box designs. If anyone is interested, let me know. I’ll be glad to inventory and post pics here, or PM. I purchased a large number of old NOS tubes from an estate and I don’t see myself using many of them. If you’re looking for an old maybe obscure tube, I might be able to help.
I've used a quad of the 6P3SE push pull for yonks and yonks at ~27W (495V 55mA) without issues other than heating up the house and burning energy.
Bought a couple matched quads from Jim McShane years ago for this very purpose. As expected, they worked very well.
What amp do you have?
jeff
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