12AX7 Tubes

Discussion in 'Amps and Cabs [BG]' started by dustinfennessey, Apr 11, 2012.

  1. dustinfennessey


    Sep 29, 2011
    Hey guys/gals,
    Looking at replacing the 12AX7 tubes in my Fender Bassman 100T. Anyone have advice on tubes? Looking for the most gain/crunch for my buck! I usually run the gain and blend on 8 or 9 so you can tell I love crunch :)
  2. bongomania

    bongomania Supporting Member Commercial User

    Oct 17, 2005
    PDX, OR
    owner, OVNIFX and OVNILabs
    12AX7's are all pretty similar in terms of the amount they clip (crunch). Also, they are the highest-gain tube in the immediate family that can be swapped in, so you have nowhere to go but down (less crunch).

    Swapping tubes may get you slightly different flavors of distortion, subtle qualitative differences, but if you need more than it's giving you already, you need an external distortion pedal.
  3. dustinfennessey


    Sep 29, 2011
    Thanks brother! You are usually a wealth on knowledge - do you have any websites that go into details about the flavor of different tubes?
  4. bongomania

    bongomania Supporting Member Commercial User

    Oct 17, 2005
    PDX, OR
    owner, OVNIFX and OVNILabs
    There are some sites like that, and several threads here talking about X tube has creamier mids and Y tube has tighter lows, but IMO they are not useful unless you have the exact same amp as the person talking. Each amp/preamp will have its own different design (the amount of voltage going to each of the tube's internal parts, for example) so they will all have slightly different response to/with different tubes. And some amps/preamps are designed so there won't even be any change when swapping tubes! The Bassman should respond to changes, but again you'll want to hear only from other Bassman owners. Or instead, just get a few different tubes and try them out. It's money, sure, but that's the best way to find what'll actually sound best.
  5. JJ 12AX7's have a lot of gain.
    Electro Harmonix is about 8 of 10 compared to the JJ's gain, but IMO have a much more harmoniclly filled tone, with an upper mid punch and responsivness that I have yet to find in ANY other tube I've rolled (and I've rolled alot).
  6. Passinwind

    Passinwind I know nothing. Commercial User

    Dec 3, 2003
    Columbia River Gorge, WA.
    Owner/Designer &Toaster Tech Passinwind Electronics
    Or maybe an amp mod. I've never worked on a 100T though, so as usual, I know nothing...;)
  7. hdracer


    Feb 15, 2009
    Elk River, MN.
    I have found the same thing. I like the Electro Harmonix.
  8. hired hand

    hired hand Guest

    Nov 6, 2007
    USA, CA, 94585
    Modern day tubes are cheap. Buy 3 or 4 different brands and see what you hear/feel.
  9. Munjibunga

    Munjibunga Retired Member

    May 6, 2000
    San Diego (when not at Groom Lake)
    Independent Contractor to Bass San Diego
    Maybe try a 7025. Still high gain, low noise. Maybe an ECC83, too.
  10. JimmyM

    JimmyM Supporting Member

    Apr 11, 2005
    Apopka, FL
    Endorsing: Yamaha, Ampeg, Line 6, EMG
    I hear differences in tubes to be so subtle that they're pretty much imperceptible to my ears. I'd leave it alone but some people like to change out tubes and say they hear differences, so what do I know?
  11. sratas


    Dec 15, 2007
    Parma, Italy
    or a linear booster...if you want to drive harder the first tube gain stage...retaining the native character of the tone.
    A distortion pedal can fit the bill, but sometimes adds its own flavour. Just a matter of taste.
  12. dj5

    dj5 Guest

    Sep 17, 2009
    I thought the same about the differences in different makes, BUT I changed a Groove Tubes for an EH and the difference was amazing - much more top end and definition.
    I suspect that the Grooves Tubes was a dud, but even if this is the case, it would still pay you to change your current tube out in case it's gone the same way.
    They are cheap, unless you go for a NOS Mullard which has been lovingly stored in a WW2 oak case for the past forty years etc etc.
    It's worth a go!
  13. Sinomis666

    Sinomis666 Guest

    Apr 16, 2011
    I found that changing the 12ax7s in my ampeg cl preamp had very little affect but when I changed the 12ax7 in the power tube driver stage things were alot more noticeable!
  14. Munjibunga

    Munjibunga Retired Member

    May 6, 2000
    San Diego (when not at Groom Lake)
    Independent Contractor to Bass San Diego
    I've put a Telefunken ECC83 in my Shuttle 9.0. I can't hear a difference, but Doug Parent can. Now, I put an identical tube in V1 of my DB750, and it made a very noticeable difference - tighter bass. However, I put a Siemens 12AU7 in V4 and it didn't make an iota of difference. So I think some amps respond differently to tube rolling from others. I did a little tube rolling in my WT-800, and didn't notice any difference in sound.

    All this from a guy who definitely lacks "the golden ear."
  15. I don't think you'll see the extra crunch your looking for out of a tube swap. You might really like the effect of a clean boost pedal to your input stage. If money is an issue you can buy a ART Tube MP preamp and use it like a clean boost to overdrive your preamp stage. You won't be able to just click it off like a pedal but they can be found very cheap. They sound great as well.

    If your wallet allows it, Creation Audio has a very nice clean boost as does Fulltone and a bunch of others.
  16. BawanaRik

    BawanaRik Guest

    Mar 6, 2012
    New Jersey
    If you don't believe tubes make a difference talk to HiTest Tubes.

    Putting a 12 ax7 in phase inverter will give you more gain. getting luck or spluring for a balanced 12at7 in the same spot will get you more bass. A great tube for this is the CV4024 from Mullard. All over the place and usually less than 30 bucks.

    Change the order of the tubes. It's free and can make a difference. To make your life much easier watch the orientation of the open spot on the pins. Putting the new tube back in the same very carefully so as not to bend the pins is good. If you're going to get into this get a pin strightener.

    Here's a link to a little more detail.

    12AX7 Tube Type Review

    But Aspen Pittmans tube amp book and buy a grain of salt to go with it. Lot's of good stuff but a little snake oil.. The JAN Sylvanias are cheap and provide a great bright v1.
  17. dustinfennessey


    Sep 29, 2011
    Thanks a lot man!
  18. bongomania

    bongomania Supporting Member Commercial User

    Oct 17, 2005
    PDX, OR
    owner, OVNIFX and OVNILabs
    ...Talk to a company that sells vintage tubes... Yeah that will get you an honest, unbiased view. :meh:
  19. majortoby

    majortoby Guest

    Jul 2, 2009
    Tampa, Fl USA
    A big +1 for the Tube MP. It does what it does very well, and it can do much. I sometimes use mine as a clean boost, or sometimes, overdrive the unit itself for a very filthy distorted tone.....but what I generally do is run the unit to the point where the LED just barely indicates clipping on the attack of a note. That seems to dial in a bit of subtle compression, with leaving enough "hair" in the sound for me to be pleased. It does introduce a small bit of noise, but I've heard that can be remedied in some way.
  20. BawanaRik

    BawanaRik Guest

    Mar 6, 2012
    New Jersey
    Bongo you might not believe it but I've talked to people who said that Gregg has spent hours with them getting their amp voiced in a way they loved. He isn't cheap, as in inexpesnive but he knows tubes.

    Spend some time rolling a few. I got a UniValve so i can afford to listen to glass at a bargin. Not a bass amp, although I've played bass through it. I may not be able to play guitar but I have some great sounding amps. And a lot of it is spending the time to get the right tubes at the right spot.

    The audio guys have been doing this for decades. Check and see what a set of NU 300s go for.

    Steve at Angela had some 6l6 jan NOS for $200 a set. I don't know if that's current but if you have over a thousand hour on the Bassman100t outputs you will notice a difference when you put these in and bias it.

    BTW output tubes generally need to get biased. Bias meters pop up on the bay every week or so.