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12AU7 Fry the BMAX-T???

Discussion in 'Amps and Cabs [BG]' started by Joe Beets, Jul 5, 2005.


  1. Joe Beets

    Joe Beets Guest

    Nov 21, 2004
    I can't turn the gain and master on mine above "1". EQ = 2, 10 and 2, para-mid neutral,, compressor off, contour and maximizer off. The gain and master controls would be less sensitive and more useful with a lower gain tube. I bet a 12AU7 would be about right. But I don't want to fry out something with this tube swap. Anybody try this yet?
     
  2. The 0x

    The 0x

    Aug 24, 2003
    Timonium, MD
    It won't fry anything.
     
  3. lo-freq

    lo-freq aka UFO

    Jan 19, 2003
    The Republic of Texas
    The typical 12AT7 would have 40% less gain than a typical 12AX7.

    If you have access to them, that might be a better starting point.

    If that's still too much, then go for the 12AU7 (which typically has 80% less gain than a 12AX7).
     
  4. Joe Beets

    Joe Beets Guest

    Nov 21, 2004
    Sounds like the 12AT7 might work best. Thanks.
     
  5. lo-freq

    lo-freq aka UFO

    Jan 19, 2003
    The Republic of Texas
    From what Tom Bowlus says, the Mullard CV4024 would probably sound good in it (if you can get your hands on one).

    Failing that, maybe a JJ.

    Good luck.
     
  6. rpatter

    rpatter Supporting Member

    Sep 18, 2004
    Round Rock, TX
    BBE has a mod for this. I had mine done and it made a huge difference. Just email their tech support.

    Ralf
     
  7. tombowlus

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

    Apr 3, 2003
    North central Ohio
    Editor-in-Chief, Bass Gear Magazine
    This does sound like a job for a 12AT7.

    The Mullard CV 4024 would give you a thicker, slightly rounded (but still with great definition) tone. I really like them, myself. I know that Doug Preston has some at a reasonable price.

    JJ's are going to be a bit more open and airy, and are an excellent new tube.

    NOS Amperex Bugle Boys or RCA's are also worth considering.
     
  8. ster

    ster

    Oct 18, 2003
    New Jersey
    +1

    I just got my unit back from BBE, now it works great.
     
  9. Joe Beets

    Joe Beets Guest

    Nov 21, 2004
    Last night I ordered a couple of Jan Phillips 12AT7WC to see if this works out. If so, I'll order a Mullard and a JJ for a tryout. Then what to do with all my unused 12AX7's. Maybe I could trade them for a classic NOS Telefunken? I'll post them in the sale/trade forum down the road. Thanks for all the info.
     
  10. tombowlus

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

    Apr 3, 2003
    North central Ohio
    Editor-in-Chief, Bass Gear Magazine
    That's a fine tube as well.
     
  11. Joe Beets

    Joe Beets Guest

    Nov 21, 2004
    My JAN Phillips 12AT7 tubes should be arriving on the brown truck today. So I pulled the BMAX-T out of the rack and pulled off the lid to get ready for the tube switch. Just for a goof, I stuck in a GT 12AU7 that was laying in the bottom of my gig back to see what would happen. I think the 12AU7 is the way to go with this preamp. I plugged my passive bass into the active input and set the EQ flat (2-10-2) and the Stewart 1.2 set slightly less than half. Now I can turn the master up to "3" and the gain all the way up to "2" so it will work out fine. Before, the master and gain couldn't go to "1" and they were so sensitive that the slightest movement of the knob could send my rig into massive overload. I wonder if I could trade my new 12AT7's to somebody for a something really cool like a Telefunken 12AU7 or maybe a NOS Mullard?
     
  12. Kael

    Kael Supporting Member

    Dec 26, 2004
    Oklahoma City
    I think that I would contact BBE to see if there is a mod that will make the gain a little more manageable as well as swapping tubes. I seem to remember reading that such a mod exists. That gain repsonse sounds completely unacceptable to me.

    I tried a Bmax-T a while back and thought that the gain was super hot. I have no clue why BBE made their gain so durn touchy. Wasn't hugely impressed with the Bmax's sound, but even if I had been I think that might have passed on purchasing one just because of this issue.
     
  13. ster

    ster

    Oct 18, 2003
    New Jersey
    Scroll up on this thread.
    I found it totally unacceptable too as some here feel that you should just keep the gain low and there wouldn't be any problems. This would be fine if nobody else ever used your rig. I was at an open mic jam and the next bassist who used my rig
    cranked the gain and destroyed my speakers. Even after I told him not to touch the gain. BTW this problem exists on the SS BMAX as well except you cannot swap tubes!
     
  14. Theoretically there isn't any problem running the gain between 0=off and 1=full, it works, except its a little hard to fine tune the gain setting to the optimal level when you have that little play to work with in the settings. Can't make any "small" adjustments.

    Sounds like its set up for passive or low output basses, and a hot bass requires way too much trim to keep from overloading. They could/should have used a pad switch or an additional lower gain/active input.

    Randy
     
  15. ster

    ster

    Oct 18, 2003
    New Jersey
    You also have to keep the volume of your bass VERY low if you have hot pickups.
     
  16. Joe Beets

    Joe Beets Guest

    Nov 21, 2004
    Both of my Fenders have stock passive pickups. Maybe I got some sort of super hot pickups through an accident at the factory. Maybe the guy who runs the machine that winds the pickup wire fell asleep and my pickups got a few hundred extra turns? I feel special now. :)
     
  17. Sounds like a piece of gear with some design problems! I've noticed quite a few negative reviews of their preamps on various threads. Hopefully, someone at the company is reading this stuff. One thing you would never want to do (IMO) is turn your bass down... unless you have active pickups, etc. you will really change the tone (treble response will be reduced, etc.) Yuck!
     
  18. ster

    ster

    Oct 18, 2003
    New Jersey
    Tell me about it! It drove me nuts. I loved the sound of the Bmax-T though so I got the mod done. It was free so that was cool but I think they should update both units.
     
  19. lo-freq

    lo-freq aka UFO

    Jan 19, 2003
    The Republic of Texas
    I'm glad that worked out for you.

    I'm surprised it's still so hot even with an 80% gain reduction.

    How much did you pay for the Jan Philips 12AT7?

    I have a couple of Jan Philips 12AX7WA I really like in my Dem 201S.
     
  20. Dan1099

    Dan1099 Dumbing My Process Down

    Aug 7, 2004
    Michigan
    I run an active bass, gain at 3-4, volume at 3-4, with no problems whatsoever, in my BMax-T. I've also ran both higher than this, with no problems as well. Sounds great!