Pentode vs. Triode....Difference?

[tunghaichuan***]

Can someone explain to me the difference between pentode vs. triode, as in the Blackheart amps? Of course, one wattage level is in pentode mode and another is in triode. I don't have a clue what these terms mean?

Thanks in advance.

The EL84 is normally a pentode, which means it has 5 elements inside the tube: anode, cathode, and three grids in between. Grid 2 normally has its own node on the power supply, but in triode mode, it is connected to the anode. This cuts the power, and makes the amp darker.

I hardly ever use the triode mode on my LG head, I just prefer the pentode tone.

tung

[jim p]

This is what I posted from what I found from modifing a Crate V5 that also has an EL84
Driving the EL84 with a signal generator have calculated the capacitance from plate to control grid to be approx 2.2pf in triode mode with the Miller effect this becomes approx 30pf this in parallel with the 220pf has a slight effect on the high frequency roll off of the EL84 (20KHz in pentode mode 19KHz in triode mode)
Some of the major changes between the two modes is output power 5 watts pentode mode and 1.5 watts in triode mode. Also plate impedance 38k ohms approx for the pentode mode 2k ohms in the triode mode the result the amplifier is more dampened in the triode mode closer to a solid state amplifier sound then in the pentode mode
So triode mode not only drops power it reduce overshoot due to inductance, capactance and other effects relative to the speaker used over all it won't sound as bright as the pentode mode. If you surf the web you will see tube HiFi folks like the triode mode with some amps that have 800-1000 volts on the plate and 300 dollar tubes.