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5881 vs 6L6 Power Tubes

RDSChicago

RDSChicago

Well-Known Member
I just bought an Onkx SP3 amp with Melody 5881 power tubes. The seller included a quad of Sovtek 6L6WXT tubes which he says will bring the stock amp from 38 to around 50 Wpc.

Does anyone have experience with both of these tubes? Would love to hear opinions re extra power and sound quality.

The manual says to bias the 5881 tubes at 1.15. Should the 6L6 tubes be biased at the same voltage level?

Thanks.
 
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The 5881 is a slightly less-powerful version of the 6L6GC, IIRC. But it's doubtful that anyone is making actual 5881s now - the stock "5881" tubes are likely 6L6GCs with alternate labels. The 6L6WXTs should also be 6L6GCs. Bias them the same. I doubt that you'll get 50 watts output from either set of tubes.
 
Original 5881 were designed for industrial use and were made to withstand extra vibration and shock, and different construction from 6l6 or 6l6gc. These different constructions can result in different sound quality. Also among USA brands, Sylvania GE, RCA and Tungsol all had slightly different designs for the same tube type. As skriefal says, the Russian 6l6 or 6p3s were all designed the same although i believe some were made with gold plated grids for extra longevity.
 
5881 was rated for approximately 20% greater dissipation than the 6L6GB. 6L6GB was rated at 19W in pentode connection, 5881 at 23W, and 6L6GC at 30W. Pushing the 6L6 design to its final limits, the 6550 was rated for 42W. They were all beam pentodes, same general construction except for the treated grids and anodes in the 5881. The European equivalents to the 6L6 family, the KTs (KT66, KT77, KT88) were electrically interchangeable but had a different internal construction. The EL34, EL35, and EL37 were all pentodes, like the 6L6 family, but weren't quite as electrically interchangeable as the KT series tetrodes.

There were a handful of other tubes in that general family, like the 807, 1625, and EL31, but they're different enough to be another discussion entirely.

primosounds said:
Original 5881 were designed for industrial use and were made to withstand extra vibration and shock, and different construction from 6l6 or 6l6gc. These different constructions can result in different sound quality. Also among USA brands, Sylvania GE, RCA and Tungsol all had slightly different designs for the same tube type. As skriefal says, the Russian 6l6 or 6p3s were all designed the same although i believe some were made with gold plated grids for extra longevity.
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RCA never made a 5881, to the best of my knowledge. Every RCA 5881 I've seen was a rebranded Tung-Sol or Sylvania. I'm not sure about GE, but I've never seen one.

There was a 6L6WGB, often double-marked as a 5881, made by Philips. There's a Tung-Sol datasheet for the 6L6WGB, which I would assume to be the same as their 5881, since the specs are the same.
 
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I have some 6L6WGB tubes in something, I think they are GE but don't hold me to that. Its been a long time since I had the lid up on that piece of gear. Physically smaller bottle than a lot of 6L6GC's, same bottle size as the couple of 5881 tubes I have.
 
A bit of ancient history - Tung-Sol introduced the 5881 in 1952 or so, Sylvania second-sourced it as 6L6WGB. Many other compaanies relabeled these two; I'm not sure if anyone else made it. It was a UP-rated, DOWN-sized 6L6 with rugged construction for the military. Since it was rated for 23W dissipation instead of 19 for the 6L6, it did get used in hi-fi and guitar amps. The 6L6GC came later with a 30W dissipation rating, and pretty much was the tube to choose from that point on. Philips US (former Sylvania) even made some GWBs with GC internals, and why not? Tougher and longer lasting, and fewer parts to stock. And then American production stopped and so did the ratings systems that industry and the military had insisted on. Many Russian 6L6 equivalents (19W) were relabeled 6L6GC, and of course they wouldn't last at higher voltages and dissipation levels. The best Russian 6L6s were relabeled 5881 (since it had a good reputation) and were really equivalent to 6L6GC. Chinese made ones are all over the map - some are very good. And 6L6WXT? Likely the same tube as the (modern) Russian 5881. And Tung-Sol (not the original Tung-Sol!) has "reissued" the 5881 in the original smaller bottle size, and I assume original ratings. NOT up to 6L6CG ratings. And if you're not confused yet, you haven't been paying attention!
 
Sam Cogley said:
RCA never made a 5881, to the best of my knowledge. Every RCA 5881 I've seen was a rebranded Tung-Sol or Sylvania. I'm not sure about GE, but I've never seen one.
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I think you are right about 5881 , but in my response i was referring to the different types of construction of 6l6 by the major tube makers and not just talking about 5881.
 
I've been using 6L6WXT's for years in guitar & audio amps repairs. Love them. Just buy them from someone that will match them close. Also Ruby STR 6L6 are a tough tube. A lot of choices & cost is all over the place but the WXT's are my favorite.
 
The German store "Tube Amp Doctor" writes this on their page about the 6P3S-e tube:

"5881 / 6L6WGC / 6P3S-E - Russia / Sov.
The russian 5881 was born as 6P3S-E in the Saratov plant and was designed for the use in military vehicles and aircrafts.
Outstanding mechanical sturdyness and reliability is its key feature.
Today this tube is mostly known as Sovtek / Russia brand 5881 / 6L6WGC which is the current production version of the identical tube.

The original military 6P3S-E tube was made to the highest standards with tights limits in quality spread.
Consequently we try to provide you with this original mil. grade 6P3S-E / Sov. if possible.
Please note that the marking on the original tube says 6P3S-E while the Sovtek says "5881 / 6L6WGC".
In case we can not get the NOS 6P3S-E we do provide the Sovtek branded item instead."
 
Tom Bavis said:
A bit of ancient history - Tung-Sol introduced the 5881 in 1952 or so, Sylvania second-sourced it as 6L6WGB. Many other compaanies relabeled these two; I'm not sure if anyone else made it. It was a UP-rated, DOWN-sized 6L6 with rugged construction for the military. Since it was rated for 23W dissipation instead of 19 for the 6L6, it did get used in hi-fi and guitar amps. The 6L6GC came later with a 30W dissipation rating, and pretty much was the tube to choose from that point on. Philips US (former Sylvania) even made some GWBs with GC internals, and why not? Tougher and longer lasting, and fewer parts to stock. And then American production stopped and so did the ratings systems that industry and the military had insisted on. Many Russian 6L6 equivalents (19W) were relabeled 6L6GC, and of course they wouldn't last at higher voltages and dissipation levels. The best Russian 6L6s were relabeled 5881 (since it had a good reputation) and were really equivalent to 6L6GC. Chinese made ones are all over the map - some are very good. And 6L6WXT? Likely the same tube as the (modern) Russian 5881. And Tung-Sol (not the original Tung-Sol!) has "reissued" the 5881 in the original smaller bottle size, and I assume original ratings. NOT up to 6L6CG ratings. And if you're not confused yet, you haven't been paying attention!
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Tom, Sylvania relabled the 5881 from Tung-Sol at first, but later on 5881s were made that were obviously not Tung-Sol on the inside and have Sylvania-style markings on the glass. I have a quad of NOS RCA-labeled 5881s here, three are Tung-Sols, the fourth is, I'm pretty sure, Sylvania.

Sylvania 5881s look like this (not my photo):
5881p1.jpg


Note the lack of the Tung-Sol vertical mica spacers and the "5881 USA" markings that are identical to Sylvania markings used on other power tubes.
 
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By "second-sourced" I meant "manufactured an equivalent", not "relabeled". I don't know if GE or others made true 5881s - I only have Tung-Sol and Sylvania.
 
Yep, that's Tung-Sol. Only other possibility, really, is Sylvania- and the Sylvanias have a narrow center vertical rib on the flat front part of the plate, and the flat part of the plate isn't as wide as those... so those pretty much have to be TS.

Back on-topic with the OP- if the original 5881s were coin-base Russian tubes (made in the Reflektor plant), or a Chinese "exact copy" of that design- then changing to a NOS or more "NOS-equivalent" version of the 6L6GC could POSSIBLY result in a LITTLE more power output. The coin-base Russian 5881s are reported, in some cases, to have a little less power output, all things equal, than a "true" 6L6GC- but we're talking like 10% at most. Usually, it's not really noticeable at all, in fact. Going from 38 watts to 50 watts- a nearly THIRTY PERCENT increase- just doesn't seem likely at all.

Regards,
Gordon.
 
Tom Bavis said:
By "second-sourced" I meant "manufactured an equivalent", not "relabeled". I don't know if GE or others made true 5881s - I only have Tung-Sol and Sylvania.
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Ah. I've seen some early Sylvania 5881s that were relabled Tung-Sols. I don't think I've seen any US manufacturers of the 5881 other than those two.

Selmerdave said:
252262389785_1.jpg


Not mine but they look identical to these.
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Tung-Sol. The six vertical mica spacers are a Tung-Sol power tube hallmark.
 
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