EL86 VS. EL84

[engels]

EL86's now sell for 2.90 at Antique Electronics. I'm planning to build a 18W with those. The tube has the same pinout as EL84 and is a bit more powerfull. They require about 50V less voltage than EL84 and draw a bit more current. The output is 18.5W in PP (vs. 17W of EL84). The load resistance is 5K vs. 8K of EL84 (should distort less with the same OT).

Datasheets:

EL84 =
http://frank.pocnet.net/sheets/010/e/EL84.pdf

EL86 =
http://frank.pocnet.net/sheets/010/e/EL86.pdf

Any comments? If your 18W has B+ under 300V you may simply stick a pair of those and see what happens. Can somebody tell me why nobody uses them?

[hucky]

this tube was introduced by philips to build ironfree (no OT) amps
paired with highimpedance loudspeakers (800 Ohm)

the main difference is the internal impedance of the tube.
to get the 18 watts you have to run the amp with lower impedance
at the anode. the easy way to get there is to run the 8 ohm speaker
on the 16 Ohm tap.

if you just swap the tube and run the amp with standard EL84 OT you get less
power and harder clipping of the poweramp.
i call this overimpedance matching or voltage limiting.
in contrast to lowerimpedance matching or current limiting
(see matchless)

to get the EL86 running with a easy mod you can run 2 of them in a
36watt (4 tubes) design.