SWR amp noise (click/pop)

Discussion in 'Amps and Cabs [BG]' started by snoopyjc, Oct 25, 2003.

  1. Well, my new Spector ReBop bass is basically "passive", even though it has a pre-amp - it is basically an isolator (has no apparent gain). Therefore, I have to turn the amp volumes up pretty high to get a good signal out of the speakers. I basically have the pre-amp volume on FULL and the Master volume on 3/4. This is on an SWR SM400S (same as an SM500).

    Here is my problem:

    If anybody plugs anything in to the power outlets in the club, or turns on/off switches, the amp will make an annoying click/pop sound. This occurs even when the volume knob on the bass is set to "0". This bothers me and the sound man to no end. When I used to have my Fernandes active bass, this wasn't a problem, because the volume controls were set MUCH lower.

    Any ideas?

  2. Rod Harder

    Rod Harder Forte Collector - not done yet Supporting Member

    Sounds like your ReBop has some issues, there is NO way that you should have to run your amp that hot with your bass to get a decent volume, and your Rebop should have more output than your Fernandes no matter if it has the Aguilar or Spector preamp. Your Rebop needs some attention, start with the battery, make sure it's fresh, and if it still has weak out put you need to have it looked at. I'm not sure what type of cab you are using with your SM400S, but it sounds like your Rebop is the best place to start looking.
  3. Sounds like bad power/ground in the club. They should get it checked. If there is a bad ground I don't know if a power condition/protector will help.

    Are you plugged into the passive input?
    Have you checked the tube? Someone may have substituted a low gain tube (5751, 12AU7, 12AT7) for the 12AX7.
  4. IvanMike

    IvanMike TTRPG enthusiast, Happy, Joyous, & Free. Supporting Member

    Nov 10, 2002
    Middletown CT, USA
    still check the bass
    i've never seen a bass that you have to turn an swr up farther than 2 o clock (and thats really pushing it even then)
    i think your bass has issues, not your amp
  5. I figured out that if I put the volume on the bass on "10" and the volume on the amp on "5" instead of vice-versa, then a lot of this noise goes away!

    I'm also going to check my pickup height - I think it's kinda low right now.

  6. Finger Blister

    Finger Blister

    Jul 8, 2003
  7. I raised my pickups (they were quite low), and now I can turn the amp volume down even further - pretty much eliminating these annoying noises. Thanks for your help!
  8. Michael Yetton

    Michael Yetton

    Dec 11, 2000
    Essex, UK
    you'll get a little pop on power up of the amp anyways. apparantly, according to SWR, they omitted a relay on the power switch, to stop signal degrade...

    it does sound a bit worrying!!!
  9. chadds


    Mar 18, 2000
    Bill Sheehan said he had an annoying pop. His mom divorced him.
  10. JMX

    JMX Vorsprung durch Technik

    Sep 4, 2000
    Cologne, Germany
    This is a curious argument, a relay is just a switch and others use relays in the signal path for just this reason IIRC.
  11. When a relay is put in the relatively low-impedance speaker signal-chain, it can degrade the signal. It adds a few milli-ohms of resistance, and also, when those contacts get dirty, it can completely destroy the signal!

    I agree with SWR when they say
    But, we're really getting away from the topic I first posted!!!

  12. De Teng

    De Teng

    Oct 27, 2003
    Utrecht, Holland
    There is always an equilibrium between a too high or a too low setting of the preamp.

    Too low: lots of hum and noise, getting nothing out of the speakers. (In a 'volume speaking way'.)
    Too high: fast clipping, and indeed, when an external electrical circuit is switched on or off, then it's clipping too.

    Your 'empirically obtained' solution was there. Open the signal of the bass fully and lower the gain of your SWR.
  13. Im a sock

    Im a sock

    Dec 23, 2002
    Central MA
    Yeah, and i dont know if the SM-400s has a speaker on/off switch, but if it does... just turn the speakers off before you turn it on or off
  14. De Teng

    De Teng

    Oct 27, 2003
    Utrecht, Holland
    Something you must always check.. at first: volume down, then switching/connecting anything.
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