Ampeg pf-350 and thermal protection

Discussion in 'Amps and Cabs [BG]' started by versicolor, Nov 6, 2017.

  1. versicolor


    Jan 18, 2013
    I'm trying to understand exactly how this works. From searching I mostly get that this is an overheating protection shut down. But what if my 350 is cutting out even after I have just turned the amp on for the days practice and is not hot at all? I have the 350 powering a pf410hlf and a mc-210E. So it's 4ohm load full 350 watts. Gain at 3 o'clock, bass at 2, mid at 11, treble at 11, volume at 2. Limiter button not engaged. It's loud at these settings but does not sound distorted at all. If I slap or strike a string hard it will cut out for about 2 seconds then come back on and play as normal. Is this simply telling me that there is too hot of a signal coming in too fast? Or should I be able to do this without the amp cutting out. I have only had this amp for 3 weeks now. I want to make sure that it cutting out is not just my error before considering exchanging it for a new one. Thanks for any help you can offer.
  2. Crater


    Oct 12, 2011
    Dallas, TX area
    Class-D amps have to have some kind of automatic protection circuit because they can't be driven beyond their rated power. It's not heat related, it's the signal level. Too high a signal and the power amp briefly shuts down to protect the output transistors. Sounds like the protection circuit is doing it's job, you need more cab and/or more power.
  3. versicolor


    Jan 18, 2013
    Ok. Thats what I was thinking too. Just wanted to make sure. That 410 cab is 800 watts rms and the smaller one is 100 watts. Probably just need to upgrade to the pf-500. Until then I guess I'll just have to watch my volume.
  4. Slater

    Slater Leave that thing alone.

    Apr 17, 2000
    The Great Lakes State
    I would remove the 100w 2x10 from the set-up. It seems like you’re overpowering the 2x10 and under powering the 4x10. Cabs with equal impedance will draw equal power from your amp no matter what they are rated.
    Ampslut, lokikallas and Aqualung60 like this.
  5. versicolor


    Jan 18, 2013
    I was wondering about that. It sounds amazing but yes that 210 is only 100 watts while the 410 is 800. But damn they sound great together.
    J-Bassomatic likes this.
  6. versicolor


    Jan 18, 2013
    So what would be better? Get the more powerful pf-500 to add to the pf410hlf or just add a better extension cab to the mix.
    The pf410hlf is great on its own with the pf350 but it does add quite a bit of punch and volume with that little 210.
  7. agedhorse

    agedhorse Supporting Member Commercial User

    Feb 12, 2006
    Davis, CA (USA)
    Development Engineer-Mesa Boogie, Development Engineer-Genzler (pedals), Product Support-Genz Benz
    Categorically not true.

    ALL amps have circuitry to protect them from illegal loads (loads that are beyond the design capabilities of the specific amp)

    The first question I would have is if the amp does this just with the 410 cabinet?

    One thing that I see more than I would expect is speaker cabinets with lower impedance than as marked, either by somebody incorrectly replacing drivers with a different part, or in some cases the original design results in large sub-nominal impedance regions.

    I have also seen factory errors where a 4 ohm cabinet was labeled 8 ohm.
  8. versicolor


    Jan 18, 2013
    I'll unhook the 2x10 today and see if it cuts out with just the 410.
  9. Mushroo

    Mushroo Supporting Member

    Apr 2, 2007
    An inexpensive quick fix would be to engage that limiter.

    An expensive and heavy solution would be to get a second 410hlf and rock the 810 stack. ;)
    J-Bassomatic and lokikallas like this.
  10. versicolor


    Jan 18, 2013
    The pf410hlf is 800 watts rms @ 8ohms
    The 210 is 100 watts rms @ 8ohms
    Thats what they say anyways
  11. versicolor


    Jan 18, 2013
    So with that limiter engaged what does that do? That would make it not cut out even with hard playing?
    lokikallas likes this.
  12. Mushroo

    Mushroo Supporting Member

    Apr 2, 2007
    A limiter "squashes" the loudest peaks of the sound wave. All other things being equal, a limiter can give you more effective/perceived volume before the amp cuts out.
  13. versicolor


    Jan 18, 2013
    Ah. That makes sense. Thanks for explaining that.
  14. versicolor


    Jan 18, 2013
    So it will stop it from cutting out yet allow me to play harder? As in strike the strings harder
  15. SJan3

    SJan3 Supporting Member

    Dec 8, 2010
    Much respect to you Aged Horse.
    But doesn't it seem that his amp is shutting down prematurely? His settings dont seem unreasonable and he has PLENTY of speaker. Couldn't the problem be the amp? I've pounded some of my amps over the years and never had one shut down on me EVER. Just my 2cents as a player but certainly could not approach your understanding/level of knowledge.
  16. Skeptismo


    Sep 5, 2011
    I had a pf 350 for about 4 years, and gigged it generally at 8ohms with a 2x10, with all sorts of different eq's. I only had a thermal shutdown once, and that was in hot stuffy circumstances (so, not a mystery).

    Long story short, your experience doesn't sound normal to me. I think you should start trying to isolate the problem. Source electricity, power and speaker cables, speaker cabs, eq's. Once you've gotten the faults to where you can duplicate them and understand the cause, you'll be in a good place to remedy the issue, whatever it is.

    As far as the limiter goes, I would think your 100 watt 2x10 would die a terrible death before your amp went into shutdown mode because the limiter was disengaged. I would be very careful, you don't want to have to replace all your equipment at once!
  17. Mushroo

    Mushroo Supporting Member

    Apr 2, 2007
    Yes, assuming there's not some problem with your equipment, as others are helping you troubleshoot.
  18. lokikallas

    lokikallas Supporting Member

    Aug 15, 2010
    los angeles
    Gain at 3 o'clock is a little heavy, if the bass is active and you also crank the gain, I could see you might have an issue. I use my 350 with a variety of cabs at various rehearsal studios regularly, but usually only through a single cab. The combination of the two might not sit well with the amp.
    alaskaleftybass likes this.
  19. agedhorse

    agedhorse Supporting Member Commercial User

    Feb 12, 2006
    Davis, CA (USA)
    Development Engineer-Mesa Boogie, Development Engineer-Genzler (pedals), Product Support-Genz Benz
    It COULD be, but without exploring what's also connected to it which could be the root of the problem, there is not way to know for sure.

    Provided the load is in fact correct, they the next step is to look at the amp.
    Geri O and SJan3 like this.
  20. versicolor


    Jan 18, 2013
    The bass is a squire vintage modified 70s jazz. Passive
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