Pre-Amp Tube Tone?

Discussion in 'Amps/Cabs Tech Corner: Amplifier, Cab & Speakers' started by UMT, Jun 20, 2008.

  1. UMT

    UMT Member

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    I just replaced my Ei EL84 power tubes in my modded Marshal DSL401 with JJ's and put a JJ 12DW7 pre-amp tube in the V2 spot. Absolutely loved it. I decided I would order another 3 JJ ECC83 pre-amp tubes to replace the original Marshall labeled tubes. Put the 3 new ECC83's in today and I'm not so sure I like the sound as much as leaving the old 3 Marshall labeled tubes. The new pre-amp tubes seem a little brighter and 'brittle'... Now, I'm talking very slight differences in tone but noticable to me.

    Questions: Does the V1 - V3 - or V4 slot have more of an effect on tone or are all 3 pretty much the same?

    Thanks,
    UMT
     
  2. rockon1

    rockon1 Member

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    All the tubes have an affect on the tone -some more than others.

    Of the strictly pre amp tubes the V1 usually has the single biggest affect on tone. Its the first stage the signal passes thru.

    Ive found the PI has a big affect too. Whether this is due to different characteristics of the tubes or just the right balance(or imbalance)isnt clear.

    Experiment and draw your own conclusions.Have some fun with it! Be careful though I ended up with hundreds of 12AX7's "experimenting" ! lol!Bob
     
  3. UMT

    UMT Member

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    I just ordered a Mullard ReIssue ECC83. Lots of good reviews with this tube in the V1 position on Marshalls.

    'Ended up with hundreds of 12AX7's' is precisely my fear also! Ha. I've got enough 'jones' without adding a 'tube jones' to the mix!
     
  4. Blue Strat

    Blue Strat Member

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    Try your original configuration and then add ONE new tube at a time. You'll be able to figure out which sockets have an effect and which tube you like the best for that particular position.
     
  5. UMT

    UMT Member

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    Mike,

    Thanks. I played around with that a bit last nite. This is my first foray into the tube thing. If I decide to get serious with some NOS tubes, I'll be looking you up.

    U...........
     
  6. UMT

    UMT Member

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    By the way, why is it that only the V1 tube slot in my Marshall DSL401 has the metal cover which basically insures that the tube doesn't fall out. (?) If V1 falls out, is there a small nuclear explosion or something?
     
  7. phsyconoodler

    phsyconoodler Member

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    It's more to prevent microphonics by holding the tube tightly with the spring.And it acts like an RF shield it it's grounded.
     
  8. Blue Strat

    Blue Strat Member

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    Yep, the first gain stage, V1, is the most likely to have microphonic or noise issues because it deals with the smallest input signal (guitar) and is subjected to the most amplification (gain). I'm not sure the shield helps at all with microphonics, but it definitely shields out radio frequency interference and "noise" from flourescent lights, etc.
     
  9. solitaire

    solitaire Senior Member

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    Yes, I agree on the input valve and the gain stages perhaps having the greatest influence on tone and the choice of valves for these position thereby more crucial. As Blue Strat pointed out these are also more sensitive to microphonics, the signal being amplified more.
     

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