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Ampeg Pro Tubes

Discussion in 'Amps and Cabs [BG]' started by geddy2, Oct 9, 2004.

  1. geddy2


    Aug 29, 2004
    Southwest Michigan
    Does anyone know what kind of tubes Ampeg uses in the svt3Pro amps? I know it's 4-12ax7's and 1-12au7, but is there alot of difference in the manufacturer? I haven't actually looked at the tubes yet to see what they are. My amp is about 2 years old, I got it second hand 2 weeks ago, and just want to change the tubes to be sure.
  2. If you aren't experiencing problems, why change them?
  3. geddy2


    Aug 29, 2004
    Southwest Michigan
    Because honestly, I don't know what the amp has been through, or how hard it has been pushed. I don't want to find out in the middle of a gig, I play every weekend, and am booked every weekend through next summer. I did hear a couple of brief distorted spots last night, the first time I tried the amp, and once I backed off the lo end settings I was fine. I'm sure it wasnt the cabinet, svt610, It never did that with the hartke.
  4. Many of us have had preamp tubes last for decades, that's why I asked, even when driven hard.

    I've got an old Hartke 5000 and its tube preamp doesn't add much grit to the sound at all, so the "distortion" you heard from the Ampeg may be perfectly fine. Or it might be the transistor output stages were getting clipped slightly if you had the lows boosted, many people say the SVT3 is a tad underpowered.
  5. I believe they come stock w/ Groove Tubes.
  6. Hawkeye

    Hawkeye Canuck Amateur

    I felt exactly the same way, which is why I purchased new Electro Harmonix tubes for my SVT 3 Pro. It's in the shop with a broken fan courtesy of a less than forthcoming E-Bay seller, so I haven't installed them yet.

    When I found out the unit was 4 yrs. old and was in a studio (potentially left on a lot of the time) it just seemed good sense to change the tubes, especially with preamp tubes being fairly inexpensive compared to power tubes.

    To back-up what was previously posted, preamp tubes can typically last 4-5,000 hours before they need replacement. Some NOS Mullard, made in the UK, military spec, 12AU7's I purchased for my home stereo preamp claim a service life of 5-10,000 hrs.

    However, since a bass amp often sits on top of a cabinet, awash in mechanical vibration from the speakers, my assumption is that a tube in a bass amp application goes through a bit more physical abuse than your typical home stereo preamp.

    Another good reason to get the tube issue put to bed, is that while you are sorting out your SVT's performance and tone, you can rest assured that the tubes aren't the issue if you run into some sonic anomalies that you don't yet understand. Having new tubes would be one less thing to worry about.

    FWIW some folks prefer tubes of Russian manufacture (Sovtek / Electro Harmonix [same as Sovtek]) compared to the Chinese-manufactured tubes.
  7. bassclef112

    bassclef112 Supporting Member

    Sep 2, 2003
    New York City, NY
    When I bought my 3PRO new 5 years ago it was advertised as "Groove Tube" equipped - the reality was one GT 12AX7 and the rest were Sovtek.
    Having said that I used it with no problems up until recently (that's another story and it wasn't the tubes). After 4 years I decided to change the tubes for something different, not because they needed it. I put in Electro Harmonix all around and was very happy with the result - an improvement IMO. However, I recently had some extra gigs and decided to see what all the stir was about regarding the "upper echelon", so I got a closely matched set of Telefunken 12AX7's that were in excellent condition.

    The difference to me was incredible. A huge improvement across the board. I've never heard my amp sound so "musical". Deeper lows, tighter mids and crisp highs without shrillness. I'm a pretty skeptical guy, but this was very impressive - a real positive change. It's not inexpensive but well worth it IMO, and they do last a long time.

    P.S. For the past several years I've taken to isolating my amp from the cab to minimize vibration tranfer. Nothing fancy - I get a bunch of large scouring sponges, the kind that are part sponge, part scouring material. I duct tape them together to make 2 pads about 6" x 9" by 2" thick and put them between the cabinet and the SKB case. A stable platform for the amp that reduces a lot of the vibration - total cost = $3.
  8. Hawkeye

    Hawkeye Canuck Amateur

    It's interesting how some audiophile performance tweaks find their way into instrument amplification. To tell the truth it seems like a natural fit.

    Big bass speakers make big vibrations. Tube (and solid state to a lesser extent) electronics are affected by microphonics and vibration of power supplies etc.

    I have considered using some Isonode (currently used on my high-end CD player at home with great results) or Vibrapods on the bottom of my Ampeg SVT 3 Pro to isolate it somewhat from the vibrations and mechanical excitations of the bass cab.

    The sponge isolators sound like a great idea. If you're into experimentation bassclef112 has proved that you can do it with a small monetary outlay. It doesn't take a lot of dough to experiement with such stuff.

    Interesting to hear about the Telefunkens. Some of those older (made in Western Europe and US) tubes really do give you a performance boost.
  9. johnvice


    Sep 7, 2004
    For this reason, I don't set my amp on a speaker cabinet. I have a SKF 6-space flight case with my SVT-3 in the top slots. Before my ME-50b, I had a rack full of gear which I have since removed. I was going to get a smaller flight case but I like this config becuase the case can sit on the floor and I can still reach the controls.
  10. + another happy EH user
  11. Somebody's told you a LOAD of it. Old Mullard and Telefunken preamp tubes were RATED for 100,000 hours use and most will far exceed even that. While modern tubes may not be as well built or tonally pleasing as vintage tubes, their cathodes (the part that "dies") last even longer than in the older tubes because the they're made out of better material.

    The biggest problem with modern tubes is mechanical isolation, build quality. They become microphonic FAR easier than most of their vintage counterparts because they are not as mechanical shock resistant which makes them far more likely to short dead or "ring" sympathetically with vibration, but that condition usually presents itself within the first six months of a tube's life.

    The true rule of thumb is that preamp tubes, even modern ones, last pretty much indefinitely unless they develop microphonics. I have NEVER seen a "used up" preamp tube and I'll wager I've seen more tubes and been in more tube amps than most other posters here put together.
  12. Jerrold Tiers

    Jerrold Tiers

    Nov 14, 2003
    St Louis
    Yep +2 on that.

    Preamp tubes SLOWLY (very, very, slowly) lose emission over time, and will have reduced gain etc.

    This takes an awful long time if the tubes are used within ratings.

    I used to repair hifi stuff back in the 70's. I have actually seen "used up" preamp tubes.....generally they were original tubes that had been in-use in the equipment daily for 15 or 20 years.

    There really isn't a definite time at which you can point at the tube and say "that needs to be replaced", unless it has a specific defect, microphonics, a bad heater, a crack in it, etc.

    The emission material on the cathode gradually becomes less effective, some falls off or is knocked off by various mechanisms, etc. This takes a long time. The gain changes slowly.

    Eventually, it may be too little. At some time, you may notice that the unit "doesn't sound the same". Then there is no harm in trying a new tube. If it sounds better after that, possibly you "needed to" replace the old one.

    If the heaters are run over their rated voltage, all bets are off. I have seen some hifi equipment (mostly more recent "audiophile" stuff) that ran 6.3V heaters at 7V or higher. That may boil off cathode material faster. So may extremely high plate voltages, or attempts to use preamp tubes to produce significant power output. Hardly any units do that.

    Another thing might be tubes run at their maximum gain in a particular circuit. Some amps do have very high gains on certain stages, and loss of gain in the tube may be noticeable much sooner with those units.

    But even then, the tube will be fine for other less demanding positions in the same unit.....it isn't "bad".

    I don't care what we or any other manufacturer may say about retubing after "X" amount of time. Such statements are generally BS.

    The test of a tube is if it works in the unit, no matter how old it is. The clock and calendar don't matter.

    It isn't "worn out" until your ears say that a new one sounds better.

    By that criterion, some tubes are "worn out" as soon as you plug them in :D But that is another matter.