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Thread: Pentode vs. Triode....Difference?

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  1. #1
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    Default Pentode vs. Triode....Difference?

    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.
    Guitars: 2003 and 2004 American series strats, Squier Classic Vibe 50's Strat, Squier Deluxe Strat.

    Amps: Line 6 Spider IV 120, Vox AD50VT 212, and Peavey Transtube Bandit 112.

    Pedals: Digitech Bad Monkey.

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    Quote Originally Posted by TS808
    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
    I was just a regular guy. My only super power was being invisible to girls.
    - Dave Lizewski, Kick-A$$

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    Default pentode/triode mode with EL84

    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.

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    Quote Originally Posted by TS808
    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.
    In simpler term, triode is half of pentode. When you flip the switch it cuts off half of the tubes.
    _____

    GUITARS - Carvin DC127M - Carvin Bolt kit
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    Quote Originally Posted by kiteman
    In simpler term, triode is half of pentode. When you flip the switch it cuts off half of the tubes.
    The tone is definitely not as brilliant as in pentode mode and does of course break up earlier. I like jumping back and forth between the two though.
    Guitars: 2003 and 2004 American series strats, Squier Classic Vibe 50's Strat, Squier Deluxe Strat.

    Amps: Line 6 Spider IV 120, Vox AD50VT 212, and Peavey Transtube Bandit 112.

    Pedals: Digitech Bad Monkey.

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    Quote Originally Posted by TS808
    The tone is definitely not as brilliant as in pentode mode and does of course break up earlier. I like jumping back and forth between the two though.
    Agreed, I use the triode mode a lot. It sound softer compared to pentode.
    _____

    GUITARS - Carvin DC127M - Carvin Bolt kit
    AMPS - Bogner Alchemist 112 - Blackheart Handsome Devil half stack
    FXs - Roger Linn Adrenalinn III - Boss GT-10
    _____

  7. #7
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    Default pentode vs. triode mode effect

    I posted earlier what the changes were in the amplifier that I modified to have both pentode and triode mode. An analogy to what the triode vs. pentode mode is like would be dribbling a basket ball with the output transformer and speaker the ball your hand the output tube. In the pentode mode it is like bouncing a well inflated basket ball easy to bounce and will continue to bounce by it’s self for a while when you stop (the bounce being the harmonics or high frequencies you hear). While the triode mode is as if you took air out of the ball, you have to work harder to bounce the ball and it stops quickly if you stop. So in the triode mode more power is lost across the output tube with less power to the speaker and the speaker is stopped quickly by the action of the tube (lower harmonics you hear as less high frequencies).
    Last edited by jim p; March 8th, 2009 at 03:45 AM.

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    Quote Originally Posted by jim p
    I posted earlier what the changes were in the amplifier that I modified to have both pentode and triode mode. An analogy to what the triode vs. pentode mode is like would be dribbling a basket ball with the output transformer and speaker the ball your hand the output tube. In the pentode mode it is like bouncing a well inflated basket ball easy to bounce and will continue to bounce by it’s self for a while when you stop (the bounce being the harmonics or high frequencies you hear). While the triode mode is as if you took air out of the ball, you have to work harder to bounce the ball and it stops quickly if you stop. So in the triode mode more power is lost across the output tube with less power to the speaker and the speaker is stopped quickly by the action of the tube (lower harmonics you hear as less high frequencies).
    Very nicely explained!
    =-) PJ

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    Quote Originally Posted by kiteman
    In simpler term, triode is half of pentode.
    Shouldn't that be semidiode or whatever the latin for 2 1/2 is.
    I pick a moon dog.

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