Power Of Various 6L6s Question

[rp]

As you go through the timeline of 6L6 types do the later ones give more power only because you can put a higher plate voltage on them or also because they are more advanced and efficient in some way? i.e. say you got 400 Pv will simply substituting a 6L6GC for a 5881 (talking NOS here not confusing modern stuff) give you a little more power?

[martin manning]

If you are around 450V, then there is little difference in the power output from 5881 or 6L6GC. The 5881 is at it's dissipation limit though, where the 6L6GC is not, and so the 6L6GC's output power can be increased by going to higher voltages.

[M Fowler]

Good info Martin, I was thinking to only use the 5881 with lower voltages so I had it in my mind to switch between (6v6 and 5881) on lower plate voltage amps and (6L6 and EL34) on higher plate voltage amps.

Learning something every day on this sight.

Mark

[martin manning]

Power is B+ and load impedance. Then the question is: What tube will match that load at that B+, and can it handle the plate dissipation.

[Dave5881]

I think the question is, at any given voltage will a 6L6 conduct more current (provide more power) than a 5881. Is there an efficiency in the 6L6 not present in the 5881?

[Leo_Gnardo]

I think the question is, at any given voltage will a 6L6 conduct more current (provide more power) than a 5881. Is there an efficiency in the 6L6 not present in the 5881?

Considering the original 5881's, size of cathode & plate. That's about all.

Sovtek so-called "5881" simply marketed to hook the attention of 5881 fans. Not a bad tube at all, very tough and can sound perfectly good with sufficient bias current, but not a copy or reissue by any means.

FWIW after using hundreds of them by now, I'm thinkin' JJ 6V6 more resembles the original 5881.

[martin manning]

I think the question is, at any given voltage will a 6L6 conduct more current (provide more power) than a 5881. Is there an efficiency in the 6L6 not present in the 5881?

No. The 6L6GC and 5881 anode curves are very similar wrt anode current at the same anode and screen voltage.

[rp]

I think the question is, at any given voltage will a 6L6 conduct more current (provide more power) than a 5881. Is there an efficiency in the 6L6 not present in the 5881?

No. The 6L6GC and 5881 anode curves are very similar wrt anode current at the same anode and screen voltage.

That's what I was looking for.

[martin manning]

FWIW after using hundreds of them by now, I'm thinkin' JJ 6V6 more resembles the original 5881.

I tested some JJ's here: https://tubeamparchive.com/viewtopic.ph ... 078#274078 and they seem similar to 6V6 except for the high screen current at the test point. JJ doesn't show pentode curves in their data sheet for this tube, so I will trace one when I get home.

[didit]

The short answer is that for given B+ and load all basic 6L6 variants are roughly the same, at least up to dissipation limits. There are differences across the types but design goal over history was to be functionally compatible, only more rugged.

The article on page 3 of this VTV from about 15 years ago may help -- http://www.vacuumtubevalley.com/Magazines/VTV04a.pdf.

Best .. Ian

[David Root]

Original Tung-Sol 5881/6L6WGB can handle plate voltages way in excess of 400V. It's the earlier 6L6GA, -G and metal ones that get uncomfortable much above 400V or so.

Subject to proper bias of course.

[martin manning]

It's not just the voltages, it's the combination of voltage and load with respect to plate dissipation. With plate and screen close together as is typical for guitar amps, 5881 is pretty much done at 450V into a 4k load. Compared to the table below, Leo pushed well beyond the rated voltages in the 5F6-A, but stayed on the right side of dissipation. Tung-Sol's data sheet says 23W Pa, but 400V max for both plate and screen.

Since this thread is not about the 6V6, I'll put the result of tracing a JJ 6V6S and comparison to GE data over in the u-Tracer thread.

[Leo_Gnardo]

Thanks for that 6L6 "thru the years" chart Martin! I'd clean forgot about the EL37. I have a couple used ones kicking around. It's a wonder one of the modern tube manufacturers hasn't tried to make a copy of this beauty. Some of the earliest Ampegs were equipped with EL37.

I'd also like to experiment with the 350B currently marketed at affordable prices, to try and get a 30's-40's sort of tone. WE 350B's last I saw were going $850 each, way way way beyond my pay scale. Last I saw CE/Antique had China made ones at reasonable cost $20 more or less.

[martin manning]

Leo, that chart is was snipped right out of the VTV article didit (Ian) linked above.

[Leo_Gnardo]

Leo, that chart is was snipped right out of the VTV article didit (Ian) linked above.

Dang I thought I reckanized it! I miss VTV. Was hoping for it to continue. Got all 20 issues.