6LF8 tube chart interpretation

[Danelectron]

http://www.shinjo.info/frank/sheets/049/6/6LF8.pdf

I was looking at some tube charts and came across the 6LF8 high mu triode / sharp cut-off pentode 9 pin tube. The tube chart describes it as being for video amplifiers and other applications using positive triode-grid operation.

What interests me is that this appears to be a very linear tube(at least the triode section). The bias voltages are a bit confusing though. I'm still a bit in the dark on interpreting these chart, but am I correct in interpreting there is a small window where the triode section can be operated negative bias? Is there any practical audio use for this tube? What about the pentode section? Could this be used for designing a very low wattage pre amp and power amp in one tube?
It appears you could build a 2 watt or so amp with this tube?
What would the sharp cut-off do?

Any thoughts or insight?

[ThermionicScott]

http://www.shinjo.info/frank/sheets/049/6/6LF8.pdf

I was looking at some tube charts and came across the 6LF8 high mu triode / sharp cut-off pentode 9 pin tube. The tube chart describes it as being for video amplifiers and other applications using positive triode-grid operation.

What interests me is that this appears to be a very linear tube(at least the triode section). The bias voltages are a bit confusing though. I'm still a bit in the dark on interpreting these chart, but am I correct in interpreting there is a small window where the triode section can be operated negative bias? Is there any practical audio use for this tube? What about the pentode section? Could this be used for designing a very low wattage pre amp and power amp in one tube?
It appears you could build a 2 watt or so amp with this tube?
What would the sharp cut-off do?

Any thoughts or insight?

2 watts is pretty optimistic, but you could design *something* around it. Just ignore the positive grid lines when drawing the load line for the triode section. With a ~150V supply voltage (plate and screen) for the pentode section, you could bias it at 3W and run it into a 5K load for mayyybe a watt.

I wonder if I have any 6LF8s in my stash...

- Scott

[Danelectron]

2 watts is pretty optimistic


Scott, I was looking at the max plate dissipation of the pentode side, but figured it would be somewhere below this for proper operation range. I'm just getting a handle on preamp design and am still lost on the power amp side. It is an interesting tube to me though. Even 1 watt would be cool if it has good characteristics. Would the volumn of an acoustic be over optimistic? I acquired 6 of these real cheap by mail order and am going to take a shot at designing something. If you're curious and can't find one lying around I would be happy to send you one for R and D purposes when they show up. I like the idea of a small combo. A fun little science project. It will take a while as I will be educating myself along the way.

Thanks for responding. I'll keep you posted as I go along

[Jazz P Bass]

Hi mu triode/ Pentode

The triode portion can be set up the same as a 12AX7.
Maybe you could use two tubes for the output section.
Phase inverter triodes & the two pentodes in push pull.
3 watts should not be stretching it.

[ThermionicScott]

Using two of them in push-pull would really open up some possibilities.

I built a 2x6AU6 amp about a year ago that puts out something like 1/8 of a clean watt. I was expecting more output, but it's perfect for the shop as is!

- Scott