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SWR transient 'Pop' on shutdown

Discussion in 'Amps and Cabs [BG]' started by ghindman, Feb 17, 2006.

  1. ghindman


    Feb 10, 2006
    I have an SWR 350x Pro, and I'm aware of the SWR explained speaker pop on power-on, but I have a similar, but likely unrelated problem. When I turn the amp off, I often get a high-frequency transient pop - sounds almost like a static discharge. It does not happen every time, and it seems to be more likely to happen if I turn the amp off just a few minutes after I turn it on. The pop is sometimes quite loud, sometimes soft, and often not there at all. I am always careful to turn both the input and master volumes all the way off before shutting down, but this has no effect, and have been unable to come up with any specific combination of actions the either always cause, or eliminates the pop. It's done this since purchase of the amp.

    I bring it up as an issue because the horn on my Avatar 2x10 is blown, and I don't drive it hard enough to have done that on my own - I'm wondering if this transient is the culprit.

    Anyone else have this problem? Again, it's on shutdown, not power-on. Should I have this looked at?
  2. This happens on the Workingman's 15 combo that our church has too. Anyone know what it is?
  3. Put a .047mfd 250 volt cap or greater across the Power switch contacts that feed the transformer. Did this on mine and now it is quiet at shutdown. One wire is ground to work the Power switch's internal lamp. The other two are going to feed the transformer.
  4. ghindman


    Feb 10, 2006
    Interesting - thanks. Did you figure this out on your own, or is it a known repair guidance from SWR?

    Don't want to blow the horn on my new Aguilar s210 ;)
  5. nad

    nad 60 Cycle Humdinger Commercial User

    Sep 22, 2005
    Not Mars
    The Overlord of Nordstrand Pickups
    My 350x did this all the time, and even though the manual states it's perfectly normal, it bugged the hell out of me.

    However, it never harmed my speakers in the 3 years the amp worked before crapping out. :rolleyes:
  6. ghindman


    Feb 10, 2006
    The manual says the pop on power-on is normal, it says nothing about shut-dow. Same with the FAQ on SWRs site.
  7. Older cars with Points in the Distributer used a cap across the contacts to keep them from burning up. This is really an old electronics fix. I have been in the business since 1980.
  8. Interceptor

    Interceptor Supporting Member

    Mar 29, 2005
    Madison, WI
    Try turning the master gain to zero before shutdown if it bothers you.

    It doesn't bother me, I've grown to like it! When I set up at a gig, hit the power switch and hear the pop, I know I have juice.

    This isn't the first solid state rig I've used that pops - Standel and Acoustic also woke up with a bang. Between the three, I've never had any driver damage from the turn on transient.
  9. Mcrelly


    Jun 16, 2003
    Minnesota, USA
    I had a SWR bass 350 silverface (pre x) and also had a pop. I took it to a SWR qualified shop and THEY put a capacitor across the power switch leads. and my POP was cured too!! cost about $65 total.