5881 vs 6L6

bloozeman1

Member
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2,339
I have a dr z Jaz 20/40 amp and have been told that I can change out the quad of 6v6btubes for 5881s. My question is this. Isn't a 5881 basically a 6L6? Would it hurt to just get 6L6 tubes and make the swap or would I need 5881 specifically? Is there a huge difference in tone from a 5881 vs 6l6 vs 6v6?
 

Diablo1

Member
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620
A real 5881 is different than a real 6L6-GC. It's a lower watt tube. However, that was true with tubes manufactured prior to the 1980s. Modern production tubes don't follow the tube specifications, and they likely use the same internal components for both tubes.
 

mad dog

Silver Supporting Member
Messages
11,207
The original 5881 is also rather different sounding than the higher power 6L6-GC. I like the NOS tung sol 5881s in a tweed bassman replica so much I've tried them in several other amps. They usually win over even my favorite old 6L6 GCs. A slightly softer sound, beautiful overdrive. But that's certainly not a general rule. Every amp seems to have distinct preference in this area.
MD
 
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7,832
I suppose it depends on what you mean by "5881" (same or similar to the 6L6WGB) and "6L6" as the 5881 is part of the 6L6 family. And by "5881" we're excluding any Sovtek offering that incorrectly may be labeled as such.

Fundamentally it's a headroom thing. All 5881s I'm aware of are short bottle ones, which mean they don't hold as much vacuum as tall bottle ones. The at a rated dissipation of 23-25W they're more than the plain 6L6GB which they were based on, but less than the latter 6L6GC - the innards seem to be sturdier than their specs reveal though, why many 5881s have run at length beyond their specs.

The 5881 compared to a tall bottle 6L6GC is bound to compress and distort earlier. There are some short bottles 6L6GCs which tend to behave much like the 5881 yet w. more lows, slightly cleaner sounding and rated to take the B+ of modern amps
 

Blue Strat

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30,723
Everyone's ignoring the most important issue. Who told you you could make that tube swap? If not Dr Z himself, don't trust them. Contact Dr Z.

There are several possible issues: Power transformer. Can it handle the extra heater/filament current required by 6L6/5881? Bias: Is it adjustable? If not, will the 5881s/6L6s be safe or run in meltdown mode.

Those are the first questions to be answered. Ask Dr Z.
 

Diablo1

Member
Messages
620
I have a few GT 6l6gc's that are also stamped sovtek 5881 under the gt stamp.:dunno

That's because Sovtek uses 5881 and 6l6GC as a marketing tool, and they don't put the effort into engineering a tube to match the tube specifications. It's the same as when they slap a label on the tube as Tungsol, and stick it in a box marked Tungsol. That costs them very little, but the consumers get suckered into believing the tube is more valuable.
 

buddyboy69

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Messages
5,075
That's because Sovtek uses 5881 and 6l6GC as a marketing tool, and they don't put the effort into engineering a tube to match the tube specifications. It's the same as when they slap a label on the tube as Tungsol, and stick it in a box marked Tungsol. That costs them very little, but the consumers get suckered into believing the tube is more valuable.

yeah i get that. sooooo, 6l6gc=5881 then?
 

buddyboy69

Member
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5,075
More like Sovtek 6L6GC = Sovtek 5881, and is not the same as either a NOS 6l6GC from the 1970s, or a NOS 5881 from the 1970s.
in this case a groove tubes 6l6gc=sovtek 5881. thats the tube im referring to. but i think i get it. nos is nos, modern is a bit different. i just had to retube my amp so i was looking this stuff up to see the diferences and theres mostly opinion on forums about these things. hard to find real info.
 

Diablo1

Member
Messages
620
in this case a groove tubes 6l6gc=sovtek 5881. thats the tube im referring to. but i think i get it. nos is nos, modern is a bit different. i just had to retube my amp so i was looking this stuff up to see the diferences and theres mostly opinion on forums about these things. hard to find real info.

You are correct that it is hard to find real info on modern production tubes. This is because the companies don't measure the tube performance and publish the datasheets. If you google tube datasheets, you will find tube data from all the long gone tube manufacturers. There used to be a lot of competition in the tube business, and the companies had to publish the data in order for radio/television/amplifier engineers to specify the use of that model and brand of tube. The best source of info on modern production tubes comes from amp techs, and they are concerned with reliability first, and practical limits on plate voltage and dissipation.
 

GilmourD

Member
Messages
1,421
You are correct that it is hard to find real info on modern production tubes. This is because the companies don't measure the tube performance and publish the datasheets. If you google tube datasheets, you will find tube data from all the long gone tube manufacturers. There used to be a lot of competition in the tube business, and the companies had to publish the data in order for radio/television/amplifier engineers to specify the use of that model and brand of tube. The best source of info on modern production tubes comes from amp techs, and they are concerned with reliability first, and practical limits on plate voltage and dissipation.
Doesn't JJ publish tube data?
 

swiveltung

Member
Messages
14,483
" have been told that I can change out the quad of 6v6btubes for 5881s..."
I think he's actually replacing 6V6's with 5881's. I probably wouldn't do that. Although it could be ok.
 

redchapterjubilee

Silver Supporting Member
Messages
1,502
I bought a 59Bassman LTD chassis that came with sovtek 5881's. When I put JJ 6L6's in it the amp had a good 3 dB of headroom over the 5881's. Could be the amp wasnt biased properly before and is now. Could be the 5881's too.
 

rstites

Member
Messages
1,686
Think about that one for a second. A vacuum is quite literally nothing. So the bigger glass envelope contains more of nothing than the smaller one? Multiplying by zero...

That's not really true. A vacuum is devoid of air particles. However, it has volume. That volume is important to the transmission of electrons between electrodes.

Think of the fact that the volume of space is important to the transmission of EM waves, while also being a vacuum.
 

hogy

Silver Supporting Member
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14,965
That's not really true. A vacuum is devoid of air particles. However, it has volume. That volume is important to the transmission of electrons between electrodes.

Think of the fact that the volume of space is important to the transmission of EM waves, while also being a vacuum.


You're talking about the physical distance between the tube's components such as cathode, plate, screen(s). Those have nothing to do with the "amount" of vacuum in the envelope. They just have to fit in there.
 

GrungeMan

Member
Messages
6,694
I bought a 59Bassman LTD chassis that came with sovtek 5881's. When I put JJ 6L6's in it the amp had a good 3 dB of headroom over the 5881's. Could be the amp wasnt biased properly before and is now. Could be the 5881's too.
5881's are about 23watts, a 6L6 is 26+ watts with more headroom and bottom end. Of course we a talking real 5881's and 6L6's.
 

lemonpaul59

Member
Messages
2,065
Think about that one for a second. A vacuum is quite literally nothing. So the bigger glass envelope contains more of nothing than the smaller one? Multiplying by zero...


The larger bottle contains more dark matter. The extra dark matter tends to slow electrons down, which gives a more pleasing effect to the ear.
 




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