1. Please take 30 seconds to register your free account to remove most ads, post topics, make friends, earn reward points at our store, and more!  
    TalkBass.com has been uniting the low end since 1998.  Join us! :)


Discussion in 'Amps and Cabs [BG]' started by Chube, Jul 2, 2005.

  1. Chube


    Jul 2, 2005
    Milano - Italia
    I hope this is the right place to post about tubes :) ...

    well, I've read there are some preamp tubes which reduce your output gain, so here's my question:
    Since my head is a Hartke3500 and I have to keep the volume knob at 1 (making it sound like crap) when we play in small places, would it be a good idea to put on a "gain reducing tube" so I can crank up the amp and get a better sound?

    What do you think?
    Thank you
  2. DaveMcLain


    Jun 19, 2005
    Cuba MO
    There are numerous factors involved when it comes to choosing a preamp tube. Tubes are rated by gain(not to be confused with output), transconductance(rise time), and current output. A 12AX7 tube should have a gain of 100, a TC of 1600 and a current output of 1.2 milliamps. What you will find esspecially with todays tubes is that a particular tube may NOT meet all of these criteria. Most of today's tubes have pretty good gain, around 90 or so but their TC and esspecially current output will be lower, sometimes by 50%! This changes the feel and tone of the amp but what is interesting is that depending on the circuit it can change it in different ways, one type my sound much different in one amp circuit vs another. Amps with complex tone controls and front end often are much more sensitive to current output, they load the tube more, other circuits this is less of an issue. For instance, many amps use the Sovtek 12AX7WA tubes, reason? They have LOW output and gain. This makes them quiet, stable and able to make it through warranty without causing any noise problems. They might be what you need, I think I would try several different styles of 12AX7's and see what you happen to like, who knows, it might not make all that much difference(most likely), but again, you might find the tone you're looking for, the changes will be subtle. For further reading check out Myles Rose's info on his website amplifierblueprinting.com he's got some good info on there about tubes, using tubes etc.
  3. Dave is right on it with his post. I just wanted to add that if the amp / pre amp is really high gain. you may want to look into a 5751 it will go in place of a 12ax7. But only has a gain factor of 70 unlike a true 12ax7 at 100. They are also mil-spec. Used by the US navy, ect. so they have an average usefull life of 8000 - 10,000 hrs. To meet US military requirements. Quite a few N.O.S. tube resellers have them. All other than the new sovteks are US made. Currently I've seen US JAN-GE US Navy bound N.O.S. 5751's around $20
  4. Erm, dont SS amps tend to have the same sound regardless of the volume?

    If you really want to turn the volume up a bit, lower the pre-gain (if there is one) or lower the volume on your bass

Share This Page