How much do preamp tubes change tone?

Discussion in 'Amps and Cabs [BG]' started by scraig, Feb 23, 2005.

  1. scraig


    Apr 15, 2004
    Virginia Beach
    Do preamp tubes change bass tone that much or is it subtle? If I desire a change in tone would changing tubes make a great deal of tone difference? I am thinking if experimenting some with a Demeter preamp. I am not unhappy with my tone or sound that I have now. This is a consideration to make my rig more versatile.
  2. tombowlus

    tombowlus If it sounds good, it is good Gold Supporting Member

    Apr 3, 2003
    North central Ohio
    Editor-in-Chief, Bass Gear Magazine
    It is generally pretty subtle, but in some preamps, it is more noticeable. It all depends on how they run the preamp. In "starved-plate" setups, it seems to have less impact - at least this is how it has been in my experience. Still, I think you can hear a difference, it just is not huge. But, it may just nudge your tone in a direction that you find pleasing. On units that run a full plate voltage, it seems like you hear more of a difference - and different tubes will sound better/worse with full plate voltage, versus starved plate. I recently picked up an early Chandler Tube Drive that runs a full plate voltage, and I heard a huge difference swapping tubes. I ended up liking an NOS Mullard the best in the Chandler, whereas that same tube was too muddy in my Walkabout (where I prefered the Telefunken smooth plate and the JJ ECC83s).

    Hope this helps, Tom.
  3. I've experimented with the more common types in my VTBP-201. To my ears, the difference is subtle, but audible. Some of the higher gain models seemed to break up more easily when you play harder in the lower register, if this is what you want. That preamp always sounds good to me, so nothing seemed too much more "right" than anything else. I never sprung for any real premium tubes like that NOS Mullard, so I can't speak to that, but I did try some 12AUX7's which sounded pretty good as well. Be careful that you don't flex things too much when switching them in and out. Try to hold the socket in place.
  4. Bongolation


    Nov 9, 2001
    No Bogus Endorsements
    With bass, it's subtle to imaginary in terms of tone, but changing tubes can make a big difference in things like idle hiss, preamp headroom and other problems.
  5. Pickebass

    Pickebass Supporting Member

    Jul 12, 2004
    San Antonio, TX
    I've tried a few tubes in a demeter pre and the one that made the biggest difference was a telefunken. It made it notably warmer and a little darker. I also tried the Groove tubes and it seemed to add a hifi seen to it, but didn't have the bass reponse I wanted.

    In most cases, since most tubes are made in a few places, there won't be a great deal of difference especially in tubes from the same place.
  6. Alexander


    Aug 13, 2001
    Seattle, WA
    Made a huge difference in my SWR - a bit warmer overall and the highs were MUCH smoother. Still not as warm as I would like, but I guess that is SWR...
  7. slugworth

    slugworth Banned

    Jun 12, 2003
    So. Calif.
    >>> Same thing here...I switched the OEM tube to a
    Sylvania JHS 5751 green label, and I got the exact same
    results. The OEM tube in the SM-500 looked like a generic
    no-name (probably Chinese) tube...

  8. scraig


    Apr 15, 2004
    Virginia Beach
    tombowless, what do you mean by "starved-plate" setups?
  9. IvanMike

    IvanMike Player Characters fear me... Staff Member Supporting Member

    Nov 10, 2002
    Middletown CT, USA
  10. Big diffrence in my YBA200 between the Sovtek and Groove Tubes
  11. tombowlus

    tombowlus If it sounds good, it is good Gold Supporting Member

    Apr 3, 2003
    North central Ohio
    Editor-in-Chief, Bass Gear Magazine
    Well, I am not a guru on this topic, but according to my guitar playing, electrical engineer buddy:

    "In basic terms, it is essentially as you might guess. Starved plate
    circuits operate the vacuum tube at a relatively low plate voltage
    (think 9-15 volts) compared to typical tube arrangements that use
    hundreds of volts.

    Without getting into too much muck, tubes can be biased into linear and
    nonlinear regions of operation. In some designs, it is desirable to
    bias the tube so that the tube operates predominantly in the linear
    region. However, with starved plate, the reduced headroom (lower plate
    voltage) reduces the range of operation where the tube can operate in
    its linear region.

    It does not matter whether the tube is "starved" or not. If overdriven,
    it will operate in a nonlinear region and eventually hard clip.
    However, with "starved" plate configurations, the same input signal
    compared to its non-starved counterpart will tend to enter the nonlinear
    regions and hard clip much sooner, i.e., with relatively lower voltage

    As a side note, most people do not appreciate this subtlety and lose
    sight of the fact that starved plate can be made to sound more like its
    non starved plate counterpart through careful design, e.g., by keeping
    the signal levels relatively low (thus keeping operation more within its
    limited linear region).

    Despite many critics out there (start flaming now if you like), I think
    that starved plate in general, is a perfectly legitimate design

    However, like all things, it is a matter of context and value. That is,
    in what context are you using the device? For distortion, some folks
    like the starved plate approach because they prefer the "grainier" sound
    and amount of distortion that is generated.

    Other people who like mild distortion prefer higher plate voltages
    because the increased headroom allows operation more in the linear
    region, thus some people claim to hear more "articulate" and "toneful"

    The other aspect is the value of the tube. That is, how important is
    the tube in your signal chain. Is it the major contributor to your
    tone, or is it there to blend in "tube color" to an otherwise"
    "uncolored" signal path?"
  12. r379


    Jul 28, 2004
    Dallas, Texas
    I'm glad for the information, Tom, but sometimes after all this tech-talk I'm left with an expression on my face like a monkey looking in the back of a watch. I gotta learn more and I'm doing so thanks to this forum.
  13. tombowlus

    tombowlus If it sounds good, it is good Gold Supporting Member

    Apr 3, 2003
    North central Ohio
    Editor-in-Chief, Bass Gear Magazine
    Been there myself! All I can say is that changing preamp tubes is actually pretty easy, and while the differences are quite subtle most of the time, I find it to be a fun process, and it can be kind of cool to feel that you have "customized" your preamp to a certain degree.
  14. Happy MurphDay

    Happy MurphDay

    Mar 9, 2004
  15. r379


    Jul 28, 2004
    Dallas, Texas

    I have experimented with different pre amp tubes and am about to do some more experimenting with an F1-X I recently aquired and a DB 659 I've owned for a while. Why not? I've got some tubes lying around so I'll see what they do.

    What I was referring to earlier was the discussion of starved versus non-starved plates. I'd never heard of that before but I have now. I can see (I think) some advantages to both.
  16. Hawkeye

    Hawkeye Canuck Amateur

    I changed out all four 12AX7's and the one 12AU7 in my Ampeg SVT3 Pro from a combo of no-name and chinese plus one Groove Tube to all Electro Harmonix.

    Result = lower noise floor (less hiss), a bit more punch in the lower registers, more articulate (more information), smoother, less harsh. There were quite noticeable changes in the amp, all for the better.

    I also changed out the Sovtek 12AX7 in my Peavey MAX preamp for an Electro Harmonix Gold and hardly noticed any difference at all. It was maybe a bit less brittle sounding, smoother, but that was it. It was probably not worth the $26.00 Cdn I paid for it.
  17. tombowlus

    tombowlus If it sounds good, it is good Gold Supporting Member

    Apr 3, 2003
    North central Ohio
    Editor-in-Chief, Bass Gear Magazine
    How do you like the 659? I just sent boogiebass a money order for his. :D Judging from the comments on the Aguilar website that the 659 runs "regulated high voltage plate power supply", I am thinking that it is a full plate voltage setup. The F-1X also appears to run a 300 volt supply, so it would be a full voltage configuration as well.
  18. r379


    Jul 28, 2004
    Dallas, Texas
    I liked the DB 659 a lot better before I played through (Are you ready?) an Ampeg SVT3 Pro/SWR Goliath II rig. For some reason that just sounded great. The DB now sounds a little too hi-fi to me. Not saying it doesn't sound good, mind you, but I may turn out to be an Ampeg guy. Never had much experience with Ampeg before that so I'm going to see if a different tube will, how shall I say this, give me more pronounced mids and slightly tamer highs. Hope I said that right.

    Right now I'm fooling with the F1-X more than the Aggie but that could change. Depends on what happens tube-wise. Not going to start swapping gear yet; I've got some experimenting to do.
  19. tombowlus

    tombowlus If it sounds good, it is good Gold Supporting Member

    Apr 3, 2003
    North central Ohio
    Editor-in-Chief, Bass Gear Magazine
    I spent an hour or so yesterday trying out different tubes in my Eden Navigator, and I will be darned if I heard any difference at all! Even the mighty Telefunken made no discernable difference. So, the unmarked tube that was in it when I bought it new gets to keep its home.

    This was a far different experience than in my Chandler Tube Drive, where the differences were substantial, and readily audible. In my Walkabout, the differences were very, very subtle, but you could hear them. But man, in that Navigator, it sounded exactly the same with every tube.

    So, my lesson learned is that the best answer the many questions is still, "It depends."

    Later, Tom.