Active Basses: To Pad or Not to Pad on Yo' Amp!

Discussion in 'Pickups & Electronics [BG]' started by NJL, Aug 10, 2005.

  1. Yes, I use a Pad with my Active Bass

    16 vote(s)
  2. No, I don't use a Pad with my Active Bass

    14 vote(s)
  3. Pads are only for my wife or girlfriend!!!

    5 vote(s)
  1. NJL


    Apr 12, 2002
    San Antonio
    Mods, please move this to amps if you think it should go there. :)

    Active Basses only on this thread:

    Do you use the Pad or Padded Input on your amp or not...

    Please discuss!

  2. Anything that drains away your signal to earth is bad!

    Pads are VERY VERY BAD!

    Pots are BAD! 500k pots aren't too bad! 250k pots are really bad!

    Cables are bad, too! (this is a capacitance issue, not a load issue, but it is STILL BAD!)

    Unbalanced signals are SO VERY VERY VERY bad (All earth loop nightmares start here)

    The very best situation would be to have a bass with no knobs feeding into a quality balanced line driver preamp (unity gain), through a balanced microphone cable into an amplifier that was designed to accept balanced inputs.
  3. We should be careful here to discern between pads and impedance switches. My amp does both at the same time - one switch is for passive, the other for active. I cannot change the input impedance without padding.

    Still, if I don't pad, I overload my amp. That, or I have to run the pre gain so low that the EQ starts to loose it's effectiveness. That is worse than anything that PilbaraBass mentioned. Speaking of...

    I agree, but not all pads do this.

    This is quite untrue. Earth loops are equally likely to occur regardless of whether the signal is balanced or not.

    However, unbalanced signal paths have no ability to reject EMI that has been picked up along the cable.

    Yes, unbalanced signal paths are often noisier, but this has nothing to do with earth loops.
  4. As you can see from the tone of my post, that I was being a bit silly...

    I agree that the very worst thing that can happen is that your signal gets "clipped". Hence, pads are most definitely needed (but not to be used UNLESS needed).

    And you're right about EM interference being picked up by unbalanced lines, this is because the shield (or screen, to some) is also the signal return path. With a balanced line, this is not the case, and the screen is simply the screen, but also a ground reference (hence where the noise can come in).

    Well designed, balanced input circuits that are designed and set-up properly can have good common-mode rejection (where the noise gets in the signal) and this common-mode signal can be cancelled out and thus virtually eliminated.
  5. There is still a distinction to be made between ground noise and ground loops. No amount of common mode rejection is going to help you with a ground loop problem - this is why DI boxes often have ground lift switches.

    Also, if noise is entering the system via the shield, then again, a differential amp with common mode rejection up the wazzoo isn't gonna do anything because the shield is not connected to the differential amp inputs.

    I'm struggling with this too; If a shield is connected to ground, then there ain't gonna be no signal on it at any time. But this is going beyond the point I wished to make about ground loops.
  6. A9X


    Dec 27, 2003
    Sinny, Oztraya
    Capacitiance is a load, it's just frequency dependent.
    Agreed 100%, except maybe have some gain so that you can bring the level up towards line level and improve the SNR.
    If you have more than one pup, you can employ the same approach, mixing them after the balanced input stage, into a balanced line driver stage even using an output transformer a la Wal if that takes your fancy.
  7. NJL


    Apr 12, 2002
    San Antonio
    uh, yeah, all i asked is if you pad or not on your amp (if you have an active bass)...

  8. Stox


    Mar 18, 2005
    London UK
    I use and eden metro head with a Sadowsky Metro and a MIA Jazz Deluxe V, I dont need to pad
  9. strummer


    Jul 27, 2005
    Yes, I'm a padaholic. The reason is that without pad on my Aguilar AG500, boosting the on-board clips the input stage, and that is not to my liking.
  10. tplyons


    Apr 6, 2003
    Madison, NJ
    I don't pad unless I have to.
  11. NJL


    Apr 12, 2002
    San Antonio
    You I started this thread because of another thread....

    I decided to try no Pad on my gigs this week - I seem to like it much better, but i'm still tweaking....

    I have yet to vote on the poll... :D (I have always used a pad, but may be changing for what may seem to be working for the better.)
  12. DaveDeVille

    DaveDeVille ... you talkin' to me ?? Supporting Member

    well now ...
    yeah , while using my active Valenti bass .

    i used the Pad switch on my SVP PRO for the first time at an outdoor
    gig this weekend ... i decided to try it after reading your first post.

    so , to answer your original question , yes , i will use it more often ...
  13. Nino Valenti

    Nino Valenti Supporting Member Commercial User

    Feb 2, 2001
    Staten Island NYC
    Builder: Valenti Basses
    I haven't used the Pad on my amp for years. IMO, it seems to compress the sound of the bass and always, to me, sounds better if it's not padded.
  14. DaveDeVille

    DaveDeVille ... you talkin' to me ?? Supporting Member

    yeah , it did seem to compress the volume , but at the venue i was
    playing , my normal volume setting was causing distortion ...
    so maybe i need to invest in a good compression unit ?
    what do you think ... ?
  15. What if you have a passive bass? :p
  16. In a balanced system you can actually do something about it if you have noise due to a ground loop. Because you don't need the shield as a signal reference, you can disconnect it at one end. The shield will be just as effective but the grounds of the sending and receiving devices will be isolated and less likely to cause a loop between the devices... This is exactly what the ground lift on a DI does.... Of course, this isn't really applicable between a bass and an amp.....;)

    But between a mixer and an EQ or an EQ and a power amp, being able to lift the shield at one end is very useful.
  17. smperry

    smperry Moderator Staff Member Gold Supporting Member

    Nov 3, 2003
    Bay Area, CA
    Endorsing Artist: Martin Keith Guitars
    I marked yes, because my FBB is much louder than my Ritter. When playing live or just practicing with my band, it's easiest for me to just plug the FBB into the active input so that volume changes aren't too crazy when I switch basses. Even though the Ritter is active, I use the passive input, because it's not too loud for it.

    If I'm on my own just playing through my amp, I don't use the padded input of my pre-amp.

  18. Think of it like this, the shield cuts down on stray EM that makes it into the signal handling wires. In unbalanced, any signal that makes it through is "injected" into the signal path.

    In unbalanced lines, any stray EM getting through the shield still gets onto the signal wire and from there sneaks into the signal path. But for balanced lines, with both signal wires in close proximity, the EM affects both wires equally, and the effect is that they cancel each other out. Add +1v to both wires, the result is 0v of noise added since the input voltage is the DIFFERENCE between the 2 signal lines. What's the difference between -2v and 2v signal? 4v. Now add 1v of noise to both. What's the difference between -1v and 3v? Still 4v. The input reacts to the difference between the signal lines. Simplified, but you get the idea.

  19. As far as pad or no pad? If I have to run my input gain way down to keep from clipping, I use the pad. If the pad makes me turn the input gain way up to get full signal, I turn the pad off.

    Active/passive, doesn't really matter, its how hot the signal is. If you have a high output passive bass and a low output active bass, it could be that you use the pad for the passive bass, but not the active. And that would be correct.

    Whichever pad position puts my input gain between 50% and 75% range is what I'll use. I don't want my input gain down by 25% so any slight nudge results in huge change, too hard to fine tune the clip threshold. I don't want my input gain at 100% and not clipping the input, then the pad is cutting the signal too much. Whichever pad position keeps the input gain closest to the 50-75% range is the right one. Gives you a nice comfortable adjustment range for input gain. Personal preference, nothing wrong with the input gain at any position that clips only seldom. But its just easier to do fine adjustments if you aren't crammed all the way at one end of the dial or the other.