EL84 vs 6v6

Discussion in 'Amp Central Station' started by johnnykf, Feb 21, 2006.

  1. printer2

    printer2 Poster Extraordinaire

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    Triode mode has plate impedance and lower distortion which makes it sound more sterile as compared to big bad pentode operation. Ultra-linear is partway between triode and pentode operation, the sound is also partway between the two.

    There is less advantage to running a EL84 in fixed bias as compared to cathode bias due to the grid bias voltage. Comparing a 6V6 to a EL84 at 250V, the 6V6 needs a bias voltage of -15V compared to the -11V that the EL84 needs. That 4V difference is added heat and power developed by the cathode resistor, the EL84 will waste less potential audio power than the 6V6 in a cathode biased circuit. Mind you it is more sensitive due to the added power used by the heaters. It was designed to be more sensitive so an added gain stage was not needed to drive it. By eliminating one gain stage the manufacturer saved money. As our amps run higher voltages the bias voltage is also higher, with more losses in cathode mode as we go higher.

    Some would debate the tube as being a poor design. It was introduced to the world in the Mullard Model 510 and helped kick off the hifi craze of the 50's and 60's. An example of this is the amplifiers built by H.H. Scott, the 222 and 299 series of amplifiers. I happen to have a 299 that still works to this day. Wonderful sounding amplifier, mind you it used the higher voltage 7189 variant of the EL84.
     
  2. jefrs

    jefrs Doctor of Teleocity

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    That's very interesting.
    But I believe you can imitate the ultralinear sound by fiddling with the screen grid current.

    As for the EL84 being used for hifi, it was intrroduced at the beginning of the hifi era, everything was descriibed as hifi, but have you heard a Dansette record player, hifi it is not. Besides there are better hifi bottles e.g. ECL82, and a guitar amp is not hifi. The EL84 really was designed for cathode bias, doesn't mean you can't or shouldn't do it.
     
  3. ThermionicScott

    ThermionicScott Poster Extraordinaire

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    To add, the EL84 (and EL34) were developed at a time when the use of negative feedback was a given in hi-fi design. Therefore, the main objectives were high gain and high output -- the tube itself didn't need to be as linear as in the old triode days.

    Anybody who thinks it's a poor design doesn't understand the original objectives, or how to properly design for the tube. :lol:

    BTW, don't some of Dr Z's amps run EL84's in ultralinear mode?

    - Scott
     
  4. SnorkelMonkey

    SnorkelMonkey Tele-Holic

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    On paper or in practice Jefrs? You can push a 6V6 way above spec and they'll take it. EL84's? Mmm not so much.

    Back to the OP.

    In a nutshell I've found by a/b'ing EL84's and 6V6's both moderately biased in the same circuit (and I've found this to be pretty much the case as a whole with my ears anyway).

    EL84's have a more colored clean with pronounced mids. Some say glassy or chimey? The breakup is more raw, and brittle by comparison to 6V6's. They have their uses.

    6V6's have a more flat, neutral clean tone. Their breakup is smoother by comparison to to EL84's.

    As an all around workhouse between the two I would pick a 6V6 loaded amp over an EL84 loaded amp. But I do not rule out EL84's. Many prefer them for specific genres (and I would too if I was playing them). It's one of those things where it's good to have both if you can. Apples and oranges. ;)
     
  5. DOGMA Dunn

    DOGMA Dunn Friend of Leo's

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    If you ever get the chance to try a old Marshall 18 watt or AKA 1974x. It has some of the best el84 tube tones and break up I ever experienced. It sounds similar to the breakup of a 5e3 tweed deluxe with 6V6 tubes.

    My next build will be a clone of the 1974x with a greenback speaker.
     
  6. bluesjuke

    bluesjuke Tele-Afflicted

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    I think you summed it up very well here.

    Both are great and having had both I do lean to the 6V6s.
     
  7. schenkadere

    schenkadere Friend of Leo's

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    I have a Randall 5w with 6V6’s. First 6V6 amp I’ve had. Also the best dirt I’ve ever had from an amp. Not sure why they use different power amp tubes in the different Diavlo models but this one sounds divine!

    Oops sorry. Ancient thread. I was reading and got carried away.
     
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