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  • HPSA-500


    Has anyone had problems with the auto shut off being a bit too sensitive? It seems as though it
    shuts off quite frequently after about 5 minutes or sometimes less of quiet passages in movies or less
    than bassy music, played at lower levels. Is there any way to adjust it at all? or should I just
    increase my "sub-out" level on my receiver and reduce the gain on the amp?

    Thanks for the suggestions.

    -JustinG
    ----------------------------------
    Gear:
    Samsung PN50A650
    Yamaha RX-V2500
    Hafler DH-200
    AC130MKII/BG NEO3PDR Two-Ways
    RS390HF-4 w/ HPSA500

  • #2
    Re: HPSA-500


    > Has anyone had problems with the auto shut
    > off being a bit too sensitive? It seems as
    > though it
    > shuts off quite frequently after about 5
    > minutes or sometimes less of quiet passages
    > in movies or less
    > than bassy music, played at lower levels. Is
    > there any way to adjust it at all? or should
    > I just
    > increase my "sub-out" level on my
    > receiver and reduce the gain on the amp?

    > Thanks for the suggestions.

    > -JustinG
    Justin I have had that problem on a lot of auto on circuits. The sa240 does it also. Crank the sub-out level up and lower the amp gain. That has worked for me. The worst case is just leave it turned on don't use auto. I don't know if that amp has that option but a lot do . It does not cost a lot of extra electricity If you do that with the sa240 plate amp . I don't know with your amp if that is true, but a lot of auto on circuits are the same design.

    Comment


    • #3
      Re: HPSA-500


      That is what I thought I was going to have to do. The amp doesn't have an "always on" selection, just off and auto. Thanks for the confirmation.
      ----------------------------------
      Gear:
      Samsung PN50A650
      Yamaha RX-V2500
      Hafler DH-200
      AC130MKII/BG NEO3PDR Two-Ways
      RS390HF-4 w/ HPSA500

      Comment


      • #4
        Re: HPSA-500


        > That is what I thought I was going to have
        > to do. The amp doesn't have an "always
        > on" selection, just off and auto.
        > Thanks for the confirmation.
        Justin keep an eye on it once you try that. You might be still under warranty these circuits can break a lot. Phil

        Comment


        • #5
          Re: HPSA-500


          > Justin keep an eye on it once you try that.
          > You might be still under warranty these
          > circuits can break a lot. Phil

          I might give PE a call tonight then, I think I already have the output at +7.0 dB on my Yammy.
          Thanks for your advice Phil.
          -Justin
          ----------------------------------
          Gear:
          Samsung PN50A650
          Yamaha RX-V2500
          Hafler DH-200
          AC130MKII/BG NEO3PDR Two-Ways
          RS390HF-4 w/ HPSA500

          Comment


          • #6
            Re: HPSA-500

            Has anyone found a solution to the not-sensitive-enough auto-on or are any schematics available? I'd be surprised if anyone handed over schematics, but my HPSA500 is opened up right now anyways to modify the high pass filter. Again - I'd be surprised if there were any revelations, but I'm hoping! Since I am using an external crossover and crossing over pretty low, the amp turns off WAY too often!

            Eric

            Comment


            • #7
              Re: HPSA-500

              I don't know enough to offer any real assistance, but I have the same auto-on concern on my two amps. Hoping you get some replies offering a fix
              Paul

              The "SB's" build page
              http://techtalk.parts-express.com/sh...-4-(pic-heavy)

              Comment


              • #8
                Re: HPSA-500

                Fix Found.

                After opening up the amp and probing around a bit with an oscilloscope, the auto-on functionality is provided by a single channel of a TL074 op amp on the main amplifier PCB (not the pre-amp). The inverting input is connected to a negative peak detector which is supplied by the preamp PCB, and the non inverting input is supplied with a voltage reference to compare this peak value to. From the factory, the circuit turns on the amplifier at -5.1V, and some hysteresis is used to let the amplifier stay on until that voltage falls back through -4.1V. The pin on the op amp tied to the voltage reference is pin 5. From pin 5, there is a 20k resistor to ground (R38), 43k resistor to -15V (R39), and a 390k resistor (R37) to that opamps output (pin 7) which provides the hysteresis. By changing R39 to 100k, the voltage levels can be changed to -3.01V to turn on/-1.78V to turn off, or with a 150k the levels can be set to -2.33V on/-1.03V off. By increasing the hysteresis to >1V, the amp should stay on longer through quiet passages, and by decreasing the threshold, the amp should turn on at an input of <1/2 the original voltage.
                Attached Files

                Comment


                • #9
                  Re: HPSA-500

                  This is some great information. Are you going to make this "update" to your amp? If so, please report back with the results. Since I have little electrical knowledge (I can change out a resistor, but wouldn't begin to be able to trace a circuit or test), I don't want to modify my amp(s) until someone with your experience level says it works and has no ill-effects on the rest of the amps performance.

                  Thanks for posting!
                  Paul

                  The "SB's" build page
                  http://techtalk.parts-express.com/sh...-4-(pic-heavy)

                  Comment


                  • #10
                    Re: HPSA-500

                    I plan on implementing the change tonight with a 200k resistor (on at -1.97V, off at -0.63V), and I'll post my results following some time for testing. This should make the auto-on much more sensitive and require long periods of "silence" before it'll shut off again.

                    Comment


                    • #11
                      Re: HPSA-500

                      Any update after the changes(s)?
                      Paul

                      The "SB's" build page
                      http://techtalk.parts-express.com/sh...-4-(pic-heavy)

                      Comment


                      • #12
                        Re: HPSA-500

                        Seems to be working great so far. I haven't noticed the amp turning off in quiet passages, and doesn't take as much to turn it on either. I currently have a MiniDSP before the sub, so it is only getting from 35Hz down with a 24db/octave slope. For normal TV content, there isn't much that the sub handles - hence the auto-off being such an annoyance! I'd suggest going to a 180k or 200k - 150k might not give you as much improvement as what you'd like. Hope this helps someone out there!

                        Eric

                        Comment


                        • #13
                          Re: HPSA-500

                          This is great, thanks for posting your results. Sounds like a nice improvement!
                          Paul

                          The "SB's" build page
                          http://techtalk.parts-express.com/sh...-4-(pic-heavy)

                          Comment

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