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Hiwatt DR103 Retube for Bass Use

Discussion in 'Amps and Cabs [BG]' started by lefty_400, Apr 26, 2010.

  1. lefty_400


    May 18, 2005
    I recently scored a mint "closet classic" 1976 DR103. Its loaded with a quad of Mullards that in all likelihood have little wear on them judging from the condition of the amp. Obviously the amp sounds great with the Mullards, but at the end of the day I'd rather save them for recording when it counts. I feel like a glutton just using them for practice/jamming in my basement! lol.

    I intend to use this amp primarily for bass and was wondering if you guys had any bass specific tube suggestions for a DR103. My natural inclination was to just grab a quad of winged Cs, but then I started reading about other options such as JJ KT77s, Gold Lion KT77s, EH 6CA7s, etc.

    What do you guys think?
  2. The amp was designed for EL34s and that's what you should use. The premise that bigger tubes give you more output for bass is false. If you want to save the existing tubes that's your choice though I disagree with it. Use the amp as is for as long as the output tubes last. You could well be surprised at how long that will be.

  3. Just EL34 ! Keep the mullards or get some Svetlana, Groove Tubes. I have a set of Sovtek.. which are great, but you can get better tubes.
  4. if you feel like splashing out shuguang big bottle 6ca7's are very nice. don't recomend any of the new gold lions
  5. KramerBassFan


    Jan 3, 2009
    Mod it for bass?

    I use a 100w Marshall SuperBass which does not have much different of a output stage, and it has loads of bass.
  6. BTW there is no such thing as a bass specific tube.

  7. lefty_400


    May 18, 2005
    By "[electric] bass specific[,] tube suggestions for a DR103" I was inquiring about tubes that would work best tonally in my amp given that I will be using it for bass 99% of the time.

    For example, tubes that have early breakup characteristics wouldn't be a good choice given how I intend to use it. Neither would tubes that have a reputation for flabby low end.

    New "Legal" Reworking of my question:

    "Does anybody have suggestions for a set of power tubes to load in my Hiwatt DR103 which possess characteristics that would be desirable when engaged in electric bass amplification."


  8. didn't you see what i posted before ? Check out my signature. I know what i´m talking about. I´ve been using this amp exclusively on bass since 2001.
  9. johnk_10

    johnk_10 vintage bass nut Supporting Member Commercial User

    Feb 16, 2008
    Thousand Oaks, CA
    John K Custom Basses
    if you're not going to use the Mullards, then EH 'fat bottle' 6CA7's would be my choice.
  10. When I had my dr103 I experimented with different driver tubes 12ax7, 12at7 and u7 etc, I can't remember which one did what but one gave a little more headroom. Tones didn't change nor did actual volume.
    I wouldn't change the powertubes to anything else other than el34s.
  11. Lo-E


    Dec 19, 2009
    Brooklyn, NY
    6CA7 is just the U.S. equivalent of an EL34. They are interchangeable.

    I'm a fan of the "Winged C" EL34s, personally. Not only for tonal reasons, but because I think they hold up pretty well.

    BGMWW does have a point, though; those Mullards might live a really long life. Isn't it best to enjoy them? They won't sound like much in your closet.
  12. No they are not! They are very similar but the pin out IS different. The EL34 is a true pentode and needs it's suppressor grid, G3, grounded or better yet, taken to the full negative bias supply.

  13. Lo-E


    Dec 19, 2009
    Brooklyn, NY
    My apologies. The 6CA7 is technically a beam tetrode (although my Tung-Sol datsheet lists it as a pentode).

    The pinout is the same, however. As for use in a DR103, the suppressor grids (pin 1) are, in fact, grounded making the two tubes completely interchangeable in this circuit.
  14. The 6CA7, as I recall, has no pin 1 so yes it is usable in any EL34 amp as long as the bias is checked. It's when you try to go the other way, 6CA7>EL34 that problems occur. The only reason I reacted to your post was to save someone taking your post as gospel and getting caught out.


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