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Bought a preamp... Now I have a tube question

Discussion in 'Amps and Cabs [BG]' started by Flatwound, Apr 4, 2001.

  1. Flatwound

    Flatwound Supporting Member

    Sep 9, 2000
    San Diego
    OK, so I found a nice-looking, nice-sounding Ampeg SVT-IIP preamp for a price I was willing to pay. I really like it so far, it pretty much has the tone I'm looking for, although it'll take a while to really understand it.

    The tube question is this: This preamp uses 3 12ax7's. The tubes that are in it are probably 10 years old, which is to say original, and they are SLM Hot Rods which are some sort of re-branded Chinese tubes. Would replacing them make a big difference, and if so, what tubes should I use? I'm looking for a big, fat SVT-ish (duh) kind of sound.
  2. DanGouge


    May 25, 2000
    Changing tubes can make a huge difference in the character of your tone. Find a source for them and try a few different ones :).
  3. DanGouge


    May 25, 2000
  4. Yeah, some amps were voiced for Chinese 12AX7s; if this applies to yours, buy 'em from Lord Valve. Then if you want to try other tubes, you have a baseline to compare to. Make sure you sign up for Lord Valve's e-mail catalog, there is just an amazing amount of info there. He sent me a tube data disk with an order, but unfortunately it doesn't work. He also sells QSC PLX series amps dirt cheap with free shipping.
  5. I tried Mullard, Telefunken (Knock offs), RCA nos,GE nos, Sylvania nos, JanPhillips 7025s, and the best was the cheapest --Sovtek 12AX7WA....
    Don't ask why. They just gave me the best definition and clarity. If I want some grunge, I blend in a Sansamp Bass Driver DI.
    I use an Eden Navigator preamp which has only one tube. BTW, that is the tube that came in the amp. They can be had for $6. or $7. apeace. The amp must be voiced for it.
    I also had an Ampeg SVT4-Pro. This also used the same tubes.
    You will hear lots of negative stuff about these tubes' tone, but keep in mind that most comments are Guitar players, not bassists.
  6. Jerry J

    Jerry J Supporting Member

    Mar 27, 2000
    P-town, OR
    I agree very much with ROCKBOBMEL on this. I have an Eden Navigator and a WT-500. I tried a really nice vintage nos GE and it sucked. The Eden tubes sounded, by far, the best.
  7. Flatwound

    Flatwound Supporting Member

    Sep 9, 2000
    San Diego
    Well, I e-mailed SeƱor Valve, and I'll see what he has to say. Maybe the tubes that are in there are still OK. Like I say, I'm new to this.

    Since this preamp has three 12ax7's, trying something like NOS RCA's would be pretty pricey compared to Sovteks.
  8. Preamp tubes should usually last for the life of your amplifier, barring any unforseen circumstances.
  9. You can spend about 50 clams on a good used mutual conductance tube tester on eBay. You really can't go by whether a drug store tester says good/bad. This way you can assemble a good set where the tubes are matched internally (a 12AX7 is a dual triode tube, which means its glass envelope contains the guts of two independent triode tubes) and they're matched to each other. As far as microphonics goes, there's a very hard to get tester for preamp tubes that costs 500. For that kind of money, it's much better to let your ears be the judge. I sub a good 3-mica black plate 5751 for the 12AX7. The 5751 is a heavy-duty military tube, so it's not as prone to microphonics as the 12AX7 (and I'm crazy about the sound, very tight, balanced, and detailed compared to the 12AX7).

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