6146B Tubes

Discussion in 'Amps/Cabs Tech Corner: Amplifier, Cab & Speakers' started by nlong, Mar 24, 2008.

  1. nlong

    nlong Member

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    I just came across a guitar amplifier using 6146B tubes at richtoneamps.com. Has anyone seen another guitar amp using this power tube? They don't seem to be a drop in substitution for a more common tube. I like the tones that I've heard from it, but they were recordings and not in person.
     
  2. VikingAmps

    VikingAmps Member

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    The original SVT's used em. They have a top anode connection that's a little tricky to deal with. They were probably chosen because the Traynor amp that Ampeg "borrowed" the design from used a similar tube.
     
  3. donnyjaguar

    donnyjaguar Member

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    The 6146 is a popular tube in amateur radio RF power amp circles. I wouldn't turn your nose up at one using these tubes by any means.
     
  4. jay42

    jay42 Member

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    That's the sound of Get Your Ya-Ya's Out. :AOK
     
  5. VikingAmps

    VikingAmps Member

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    I'm an advocate of doing that daily.
     
  6. stratman_el84

    stratman_el84 Member

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    Careful, don't want to develop any inconvenient calluses! :D

    Yes, I've had experience with the 6146 tube series in many pieces of amateur radio and military surplus equipment back in my ham radio days.

    They are a powerful and efficient tube. They run at significantly higher plate voltages than the average guitar amplifier power tube, typically 600-750VDC. In PP AB1 at RF frequencies a pair is rated to produce around 120 watts(!) At audio frequencies they aren't quite as efficient and power is somewhere in the 80-100 watt range for PP AB1.

    From my experience with them in mil-surplus AM transmitter modulators, they sounded very clean, with a very flat frequency response. (They *were* designed for radio frequencies, after all.) Probably the closest tube analogy sound-wise would be to some of the more powerful amp tubes such as the 6550, KT88, etc.

    The GE, RCA and other makers' versions of the 6146 series back at that time were very late to break up and distort and were a bit hard-edged when they did, but I couldn't tell you how current-production 6146's from China, Russia, CZ, etc would sound.

    If other tubes produced there are any indication, they will probably not be quite as powerful, break up sooner, and may have a smoother/softer distorted sound.

    Personally, I'd like to try building an amp built around the venerable 807. Very powerful, cheaper than the 6146, is happy at lower plate voltages than the 6146 (although it can take just as much), very forgiving to over-ratings abuse (I had an old linear transmitter power amp I built with 807's that I regularly over-drove until the plates were cherry-red! 6146's wouldn't take that for very long at all before shorting.), and has a warmer sound in audio applications in my experience.

    Cheers!

    Strat
     
  7. donnyjaguar

    donnyjaguar Member

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    Good info on the 6146. Wasn't the 6L6 modeled after the 807? That said, designing an amplifier using 807 tubes should be straightforward.
    I don't know if there are any new production 807 tubes though. All the ones I have are pre-war or during the war from RCA model 19 sets.
     
  8. stratman_el84

    stratman_el84 Member

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    Thanks Donny!

    Yes, the 6L6 was designed as a modernized replacement for the 807. Agreed about an 807-based amp design being straightforward, that's one of the things I've always loved about the 807, it's a very tolerant, forgiving tube and will handle a wide range of operating conditions and remain stable and well-behaved.

    There are 807s available out of a couple of the Russian factories the last I checked and there's also a reportedly very decent 807 coming from the Shuguang factory in China. Prices are still very very reasonable for them all.

    Here's a diagram for a 75W PP octal-tube amplifier from the old STC (Standard Telephones and Cables, Sydney) Tube Data Manual for a starting place in case you or anyone else is interested:


    [​IMG]


    Complete data for the 807 including that schematic plus a tube rectifier and choke based power supply schematic as well as choke and transformer data is available here:

    http://www.retrovox.com.au/STC807.pdf

    I also uploaded a copy of the amplifier schematic image above here that will be much easier to read:

    http://i62.photobucket.com/albums/h103/stratman_el84/Tech/PP807.jpg

    Cheers!

    Strat
     

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