6p3s tubes

[randysmojo]

I asked about the 6p3s in another thread, but no one answered so I thought maybe this was a better place. I know they are supposed to be able to go in place of a 6L6, but are they direct replacements, or do they maybe function a little different? I hear people say that 5881's are not identical to 6L6 tubes, but I've gotten similar results with similar response to biasing, so not sure what's what anymore!

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[muchxs]

They kinda suck compared to real USA (Tung-Sol!) 5881s.

There is a lotta hype surrounding them. Soviet ICBM tubes! They must be tough!

Welll...

A real U.S. Tung-Sol 5881 dissipates around 26 watts. For comparison a crude old Coke bottle 6L6G dissipates around 19 watts. A 6L6GC dissipates around 30 watts.

A 6P3S dissipates around 20 watts. As far as dissipation goes they're no better than old 6L6Gs. Your don't want 6L6Gs in most amps manufactured after 1955.

For those who think all 6L6s are alike:

The 6L6G is the oldest version.

The 6L6GB is newer, usually a straight sided version that looks like a 6L6GC.

The 6L6GC came along in the late '50s. It's the top spec 6L6.

5881s and 6L6WGBs are variants intended for military use.



http://www.tubes.ru/techinfo/HiFiAudio/6p3s.html

The plain vanilla 6P3S is supposed to last at least 1000 hours within its maximum rating of 375v on the plate. Most amps that use 6L6s are over 400v on the plate, usually around 450v. Yeah, a lot of amps run 20% over spec on the plate voltage.

Check out the "ruggedized" 6P3S "E" version. Woo-hoo! 5000+ hours life. Those must be some tough tubes.

Look again. See how they did it? They dropped the max plate voltage down to 250v. The only amps I see with supply voltage that low are wimpy old phonograph amps using 6AQ5s.

SOOoooo....

If you want to deploy 6P3S tubes you probably wanna treat them like 2x 6V6s or 2x EL84s each. They draw close to an amp each on the filament. Max plate current is 72ma +/- 18ma. That means they might draw 90ma per tube. That's EL34 territory. Bottom line here: Relatively low voltage, relatively high current.

Then there's the glowing hype. One site says,

"This high quality beam tetrode tubes used in output stages of low frequency amplifiers"

Numerous eBay listings say they're "rare". That doesn't sound right. I can buy as many as I want for around $5.00 each. Anyone wanna sell me "rare" 12AX7s for that price?

Bottom line 2.0: They are not a direct replacement for 6L6GCs. They work o.k. in a "Prolux" style 5E3. Keep the voltage low and make sure your power transformer is big enough. If you think you've found the motherlode of cheap tubes for your old Super Reverb I suggest you keep diggin'.

 

[randysmojo]

Thanks! That tells me everything I need to know and why. You are awesome!

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[printer2]

I have one, 6N3C, that I got cheap on an auction putting in an offer of a couple of bucks and no other bids. Might have to make a Champ with it running into a 5k output transformer. I never wanted to waste a 6L6* on a Champ but I do have a big ass OT. Now I just have to decide on some circuit that can benefit from a lot of switches.

 

[BiggerJohn]

Isn't the 6P3S the tube that GT used to sell calling it a "6V6HD"? It is basically a weak kneed 6L6 wannabe. I would not use them at all of I had access to a JJ 6V6 or any decent current production 6L6.

 

[Jammin'John]

I think it is.

JJ

 

[tombob]

This is a older thread but it is the first time I've ran across what I've been thinking about these tubes. I have been thinking about getting a pair (6p3s) to try in a 5e3 tweed Deluxe project I'm starting to use as a "high output 6V6". I'm thinking running the plates around 370-380v and biasing them about 15-16 watts dissipation. Of course it's going to half the output impedence (from 8 to 4 ohm on a standard OT). I've seen matched pairs of these for as little as $14 including shipping so it's a cheap enough experiment to try.
I have used the Russian 6p3s-E, the coin based version and they're totally different tubes, the "-E" version is just a 5881 and are great tubes. I've had several sets and ran them at 475-500v with no problems and they sound great.

 

[Rick330man]

I've had several sets of 6P3S-Es. Years ago I had come across some reviews or posts explaining how these were designed to run in radio equipment and radar stations out in the middle of Siberia and other remote points, so they were overbuilt.

I stuck one new pair in a Hot Rod Deluxe I sold a friend about 2 years ago. The HRD runs at about 430 volts on the plates. It is a 40 watt amp, so 2 of these 20 watt tubes work fine. He loves the amp and says the tubes are all still going strong.

 

[tombob]

The -E version are great tubes. I bought quite a few back when they first started showing up a lot, back then you pick up a quad for $20-25. I ran a set in a Twin Reverb for a couple of years running about 475-480v.
I've never been very trusting of the regular 6p3s (non -E version) in a 6L6 amp, they're lighter duty. I think they were originally made to run 250v but I've read several reports of people running them up to 400v without problems. That's low when you're talking about Blackface or most modern 6L6 amps but staying under 400v and biasing for a 19w tube is no problem in a 5e3 Deluxe, or about any 6V6 tweed amp. I've been thinking the standard 6p3s might be a great tube for that use.