Dismiss Notice

Psst... Ready to join TalkBass and start posting, make new friends, sell your gear, and more?  Register your free account in 30 seconds.

Ampeg SVT-350H problem

Discussion in 'Amps and Cabs [BG]' started by tommer, Aug 11, 2003.


  1. tommer

    tommer

    Aug 11, 2003
    New York City
    I'm new to this forum, but have an Ampeg SVT-350H and am having some problems. It works fine for a little while (10 minutes), then when I'm really getting into playing, it starts cutting out. I can smack it on top with my fist and it cuts back in. This is more prone to happen on lower notes. Has anyone had any similar problems?

    I believe it's the head because I have tried different cabinets and a new speaker cord with the same results.

    Thanks for any input or suggestions.

    Tommy Napalm
    www.napalmstars.com
    :confused:
     
  2. Ok, a few questions for you.

    What impedence load are you running on the amp?
    4 Ohm? 8 Ohm?

    Have you ever ran it with anything less than a 4 Ohm load?

    The reason I ask the two questions above is that I have had the same thing happen to my SVT 350H.
    The problem showed up when I was running the amp with a 4 Ohm load. It worked fine with an 8 Ohm load.
    What had happened is that I loaned the head to a friend of mine and he hooked up 2 4 Ohm cabs to it and ran it that way for around an hour and a half. It fried one of the sets of Mosfets in the power amp. I'm not sure which set as I replaced all 3 pairs. Cost me about $30 in parts and a few hours of my time but the amp runs fine now.

    If your not good with soldering and working with static sensitive components do not try this at home, just take the head in and have it serviced.

    If you have had it less then 5 years it's still under warrenty.

    Scott
     
  3. BillyB_from_LZ

    BillyB_from_LZ Supporting Member

    Sep 7, 2000
    Chicago
    It could be as simple as a problem with the fx loop.

    Try running a short instrument cable between the fx send and fx return. I've read that the low quality jacks that Ampeg uses in these amps can cause problems. The fx return is a switching jack that removes the connection to fx send when a cable is plugged in.

    Since the problem seems more pronounced with low notes...read more vibration, this could be the problem.

    If it is, you can either repair/replace the jacks or just leave the short cable in place.

    Keep us posted!!!
     
  4. tommer

    tommer

    Aug 11, 2003
    New York City
    Thanks for the quick replies...

    OneWayPunk: I am running the head on an 8 ohm, 18-inch cabinet. I bought this used, so I'm not sure what the previous owner had done with it or how long they owned it. The head will most likely go into the shop this week. Thanks for your input.

    Billy B: I'll try your trick with the fx send/return. Thanks for the tip.

    If anyone else has any suggestions or similar experiences...I'd like to hear 'em!

    Tommy
    www.napalmstars.com
     
  5. BillyB_from_LZ

    BillyB_from_LZ Supporting Member

    Sep 7, 2000
    Chicago
    Is the amp sitting on top of your 1x18 cabinet when it cuts out?
     
  6. tommer

    tommer

    Aug 11, 2003
    New York City
    I tried it both on top of the cabinet and beside the cabinet (even put it on a pillow). Same results. I've tried it with other cabinets and the same results. I think it's something inside that a tech needs to fix. Thanks.

    Tommy
    www.napalmstars.com
     
  7. OiBass

    OiBass

    Apr 9, 2003
    Columbus,OH
    These heads have a problem w/ clipping due to
    that they are Solid State, and the limiter likes
    to cut your power out even without the limiter
    switch on if you overdrive the speakers even a
    little. If you plan on keeping this head, I'd
    suggest an 8-ohm 4-10" to go w/ your 8-ohm 18"-
    (total 4-ohms which will give you your full 350
    watts) These are great amps when run at 4-ohms w/
    plenty of speaker area.
    Until you can get another cab, roll back on the
    gain, and the bass frequencies, and you should
    reduce your limiter cutting your power out.
     
  8. tommer

    tommer

    Aug 11, 2003
    New York City
    Hmmmm....so this is something that just happens because it's solid state and may not be fixable by technician? I'll try rolling back the gain and the lower bass frequencies and see if that helps.
    Thanks, OiBass.

    Tommy
    www.napalmstars.com
     
  9. Stu L.

    Stu L. Supporting Member

    Nov 27, 2001
    Corsicana, Texas
    Mine has never done that, but it does like to take a few minutes to cut on occasionally.

    Maybe (for whatever reason) the limiter is engaging? I think the additional 8 ohm cab may be the way to go.
     
  10. OiBass

    OiBass

    Apr 9, 2003
    Columbus,OH


    Not just becouse its solid state, it just seems to
    have a very sensitive limiter. Running it w/ an
    8-ohm load only gives you 200 watts, meaning no
    headroom, meaning limiter shutting down your signal- Mine would shut down all the time with an
    8-ohm load-and I bought it brand new-I got another cab so it would run at 4-ohm and now its
    happy.
    Another tip- put your gain & volume knobs at 0,
    dial up your gain until the peak light flickers
    when you strike a low note w/ your usual attack,
    then dial it back a little- then adjust your
    volume knob where you need it
     
  11. tommer

    tommer

    Aug 11, 2003
    New York City
    OiBass,

    Thanks for explaining that to me a little better. I'm not too educated on ohm-age. Is there somewhere online that explains ohms/watts more?

    I'll try it with another 8 ohm cabinet before I send it to a technician.

    Thanks for the tip on the gain and volume knob settings, too. I'll take any advice/help I can get.
    :)
     
  12. Stu L.

    Stu L. Supporting Member

    Nov 27, 2001
    Corsicana, Texas
    Tommer, how about a compressor? I got to thinking last nite, and I was running into problems with not being loud enough. After adding a Boss compressor, I never set the master much past 2-3, and the gain past 12. It worked for me.
     
  13. tommer

    tommer

    Aug 11, 2003
    New York City
    Thanks for the suggestion stubi19. I'm gonna try plugging in another 8 ohm cabinet this weekend to see if that cures my problem.

    I'll try using a compressor too. Are you talkin' a little foot-pedal compressor or a rack mounted comressor?

    Tommy
    www.napalmstars.com