Opinions/knowledge of Russian 6P3S

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How do you rate Russian 6P3S?

don't know
12
48%
wouldn't touch them
1
4%
solid-reliable but nuthin' fancy
1
4%
great value for $$
9
36%
sonic heaven
2
8%
 
Total votes: 25

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tubeswell
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Opinions/knowledge of Russian 6P3S

Post by tubeswell »

These look like an interesting and cheap alternative to 6L6s

Anyone tried them? What do you think? (NB: I cast my vote in the "don't knows" FWIW)

http://scottbecker.net/tube/sheets/084/6/6P3S.pdf
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Post by zaphod_phil »

I've used them, with good results. But I generally prefer EL34s to 6L6s or their Russian equivalents.

FYI from one of my previous posts:
...the original 6L6 and 6L6G's dissipation limit was 19W. The 5881 (mil-spec 6L6GB) was 23W, and the 6L6GC 30W. The 6550 has a max dissipation rating of 40W, while it's near equivalent the KT88 is rated at 42W.

The 6pi3c is also commonly marketed as the "Sovtek 5881", which with a safe dissipation above 30W, isn't a true 5881. Here is some information I've gleaned in the past about this valve.
A friend of mine near NYC has tested these with a high-voltage supply and found that they will dissipate almost 42W before the plates start to glow. I've tested them as high as 40W (approx. 500V @ 80mA) for red plate conditions in a darkened room (when you can see even the smallest trace of red glow.....). Definately not a regular 6L6GC. It can handle rather high voltages (I've heard rumors of 600VDC not being a problem as long as idle current keeps disspation below specs...). The 5881 nomenclature for this tube is really misleading, as they perform like a slightly-higher-transconductance version of a 7581A or 7027A.... Very hard to kill. I've been using a quartet at 500VDC (with a healthy 45mA of idle current) in a musical instrument amp for at least a year with no signs of weakening. No emmision burn on the glass (even when viewed in front of a clean, white sheet of paper), no rattles, no bad sounds. They've been pumping out 35W/channel all this time...They seem to require a few volts less bias than a 6L6/7027--typically needing -44V to -48V where Fender amps state -48V to -52V on their schemo--and so, sound cold/overbiased and kinda nasty when you don't adjust them for a specific quiescent current.

Dutch
So they appear to be safe for operation at around 30W to 35W, which puts them somewhere between 6L6GCs and 6550s. I've never heard of anyone using these in an 18W style amp, although a few people have been known to use 6L6s.
And here's a post from the tube guru "dotfret":
There are two basic Russian designs of 6p3s, one of which is like a 6L6 internally, and the other is an original Russian design.

It is possible to use a 6p3s of either design in any place that was designed for a 6L6, and they will usually work in place of a 5881.

Some of the Russian designed 6p3s will work in place of 6L6GC, but not all of them - you have to check them out, if they don't redplate they're fine - but when they do work they often give a cleaner sound, and less hum.

Here's a pic of a 6p3s-e that is OK in place of a 6L6GC - made by Reflector, Saratov, Oct 76 with the OTK diamond mark which designates it good for military use. The "e" suffix should mean "ruggedised envelope construction" and nothing else, but sometimes it might mean more (they could not change the specs once they were written down).

Image


I'm using these with no problems, replacing 6L6GC.
That 6pi3s-e looks identical to the Sovtek 5881, with it's oval slots in the anode and thin wafer base.
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Post by tubeswell »

Well a couple of these arrived in the post this morning, so if I get a chance I'll step them up in one of my amps this coming w/e and give it a blast. Turns out that the chap I bought them off has both types, so I'll get the other type next week.
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Post by tubeswell »

I found some time to set them up today. The datasheet that arrived with each of the tubes were all in Russian, and I could only guess at what some of the words and numbers related to, but I am assuming that they are a 6L6G equivalent, (i.e.: assuming they are a 19W tube) and have biased them to 13.6W. So far they sound okay.

If I could work out how to post attachments, I could upload the datasheet (sides 1 and 2) that arrived with each tube, which I scanned.

Edit: one of the guys at ampage pointed me to this handy eng translation

http://www.rutubes.com/index.php?productID=176
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Post by zaphod_phil »

That's way cold. 6L6GCs are 30W tubes. The Russian ones of the kind in the picture (6pi3s-e aka Sovtek 5881) are good for more than that, probably around 35W, since they only start to red-plate at around 42W. Also if this is a cathode-biased amp of the Marshall 18W topology (remember we only deal with those on this site), then you might bias anywhere between 80% and 100% of max dissipation, depending on the size of cathode cap you're using. Smaller cap sizes are used with hotter bias.

That data sheet is also total baloney in terms of maximum voltages, as well as dissipation ratings. These tubes will happily take 500V, possibly more. They're tough as nails. I recommend re-reading the quotes I previously posted.
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Post by tubeswell »

Yep read the quotes again thanks Phil. The ones I've got are just the 6P3S, and they sound fine. This particular amp is fixed bias with bias wiggle trem, so I don't want them idling too hot. I've also ordered some 6P3Se, so I will get to try those soon.
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Post by zaphod_phil »

This particular amp is fixed bias with bias wiggle trem, so I don't want them idling too hot.
Just please keep in mind that if the amp isn't a Marshall 18W style design then our companion site PPwatt.com would be where it should be discussed.
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Post by rmoody »

Haven't posted here much.

I know from experience that the standard 6P3S (not -e) will not stand up to higher voltages that a 5881 or 6L6GC will stand up to - fireworks very quick. Have tested them in a few of the bigger fender amps like twins and super twins.
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Post by StarGeezers »

Got some of these 6P3S on the way to try out ... will report back asap.... I do however Love the 6P1P ev s... a quad of those gives a nice Marshally' 18 watt sound ... brighter British sounding ... 8) ... and LOUD!!! :o :thumbsup:
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Post by zaphod_phil »

I know from experience that the standard 6P3S (not -e) will not stand up to higher voltages that a 5881 or 6L6GC will stand up to - fireworks very quick.
In that case they're not good 6L6 substitutes, and IMO should be avoided.
Last edited by zaphod_phil on Wed 09/29/10 9:40 am, edited 1 time in total.
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Post by StarGeezers »

Oh Great !!! Now he tells us .... :o 8O I'm screwed... :(
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Post by zaphod_phil »

Swap them for 63PS-e if you can!
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Post by tubeswell »

FWIW I found another claim that says they are a 20W tube.

http://timelesson.blogspot.com/2010/02/ ... trode.html

(There is a link to a Russian site on that page which is out of my league, Anyone fluent in Russian Cyrillic?).

Those (6P3S) ones I've got are idling at 445V biased to 13.6W and they seem to be holding up, although they do creak and groan a bit on power down (but I read some other reports of that being normal). I suspect that if you treat them like a 19W 6L6 and not a 6L6GC, they may be alright. I had them going for about 1/2 hour the day before yesterday. I going to run them for a while this weekend and see how they hold out. They do sound good.
Last edited by tubeswell on Wed 09/29/10 5:45 pm, edited 1 time in total.
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Post by StarGeezers »

ZP, too late now , they're in the mail ... :oops:
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Post by tubeswell »

FWIW some more info on actual experiences with the 'e' types here (especially Steve Connor's observations)

http://music-electronics-forum.com/t2925/

and here

http://music-electronics-forum.com/t12151/
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Post by zaphod_phil »

I looked at those posts, and here are some further comments:

The 6pi3-e aka Sovtek 5881/6L6GCWX was used in servo systems of Soviet aircraft as a series regulator. So it was basically being used to pass fairly high currents at low voltage. The 250V max voltage rating simply reflects that no one tested it at higher voltages.

The Sovtek 5881/6L6WGC name is misleading and self-contradictory, since 5881s are rated for 23W max dissipation and 6L6GCs are rated for 30W. The "W" in 6L6WGC also denotes a special or extra-rugged version. So it appears that Sovtek decided to use the "5881" in the West for their marketing name, to highlight the fact that these are military/aerospace tubes, like the original 5881. Unfortunately, that name doesn't reflect the tube's true capabilities.

I'm pretty sure that one of the 6pi3s-e tubes that Steve Conner tested was faulty, since it red-plated quite quickly. The vast majority of these tubes that have been put to use by many builders and manufacturers, as well as myself, run happily to 30W and above. A few years back Marshall was shipping these stock in their JTM45 and Bluesbreaker RI amps. However, I wouldn't generally run them at 40W, just to leave some safety margin and preserve tube lifetime. IMO 30W to 35W should be enough.
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Post by dotfret »

Phil is probably right, and I'm thumping them to bits. The peculiar output transformer design of the Bulk Poppy I use them in is probably the saving grace - but they stand it ... they go a long way past "the paper spec" ...
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Post by bigbeck »

StarGeezers wrote:ZP, too late now , they're in the mail ... :oops:
They may still work ok for you as you'll only be running around 380V on the plates. If not, AES has Sovtek 5881's for only 28.00 per pair. They also have the coke bottle China tubes for 17.00 a pair.

I looked on ebay for the 6P3S-E and they're 38.00 per pair plus 14.00 shipping.

I've used both the Sovtek 6L6 WXT+ and the China coke bottle with good results
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Post by gwtekman »

I used Sovtek 5881WXT's in the Ampeg VT-60 I used to own. They do great.
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Post by dotfret »

If you want to test the limits of CCCP engineering push the Russki g807 to their limits. Because the OP transformers available and the sockets are uncommon, and they need anode caps, people avoid them. They are real KT family, there are some nice circuits to work from, they make a better fit with the 18W than a lot of other valves. WTH they are cheap ...
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