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Niles amplifier thumps when power off

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  • Niles amplifier thumps when power off

    Hi!
    I got an used digital Niles SI-250 amplifier (link below) that thumps only when turned off.
    I 'm worried it can damage my loudspeakers as the woofer cone moves so far.
    Any experiences with this amp?
    THX
    http://www.nilesaudio.com/product.ph...rdcdID=FG01701

  • #2
    Are you using the front power switch to turn off the unit or are you cutting the AC to the amp using some external control (e.g., power strip switch)? Also, have you tried the auto sense turn on/off to see if the same problem exists when the amp turns itself off?

    Comment


    • #3
      It probably relates to the order that you power up and power down your components - try shutting off the Niles power amp before powering down the pre amp or AV receiver that is feeding the input of Niles power amp ;)

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      • #4
        To Mike and Coke thanks for your reply. I've tried all yours suggestions and the problem remains.

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        • #5
          Originally posted by abn1701 View Post
          To Mike and Coke thanks for your reply. I've tried all yours suggestions and the problem remains.
          Is it a 2 prong plug on the amp? You might try flipping over the amp cord into the wall outlet/receptacle. You can if the amp cord/plug isn't "polarized" otherwise you'll need an adapter. Sometimes you can install (if you know how) a sparking capacitor across the On/Off switch contacts and that will kill some of the On/Off pop, but not necessarily the thump. I almost always retro fit my equipment with a sparking capacitor across the On/Off switch. A "thump" is usually a large current draw, which would benefit from some sort of soft start. If the amp never thumped until now, then that would be indicative of a growing problem.

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          • #6
            Some amps do that, it usually isn't a problem. I can't say if it's normal for this amp.
            www.billfitzmaurice.com
            www.billfitzmaurice.info/forum

            Comment


            • #7
              Agree with Alan here about the soft start. However, stick to the following start up and shut down sequence to prevent thumping your speakers:

              Start up: Amp --> Preamp --> Source

              Shut down: Source --> Preamp --> Amp

              Let us know if this helps.

              Hong
              Some people are addicted to Vicodin. I'm addicted to speaker building.

              The Chorales - Usher 8945A/Vifa XT25TG Build
              ESP Project 101 Lateral MOSFET Amplifier
              LM4780 Parallel Chipamp
              Sonata Soundbar Project
              The Renditions - Active/Passive Towers

              Comment


              • #8
                Hong, that's exactly backwards of what I do and what I'd recommend!
                Paul

                Originally posted by hongrn View Post
                Agree with Alan here about the soft start. However, stick to the following start up and shut down sequence to prevent thumping your speakers:

                Start up: Amp --> Preamp --> Source

                Shut down: Source --> Preamp --> Amp

                Let us know if this helps.

                Hong

                Comment


                • #9
                  Heck, you're right Paul. I'm allowed one stupid mistake a year, am I not? All my built amps have soft starts, so I guess the sequence doesn't matter, hence MY confusion. Sorry abn1701.
                  Some people are addicted to Vicodin. I'm addicted to speaker building.

                  The Chorales - Usher 8945A/Vifa XT25TG Build
                  ESP Project 101 Lateral MOSFET Amplifier
                  LM4780 Parallel Chipamp
                  Sonata Soundbar Project
                  The Renditions - Active/Passive Towers

                  Comment


                  • #10
                    Yep, you're allowed one stupid mistake a year, and when you get to be my age, you're allowed to have numerous "senior moments" all year long, stupid or otherwise!
                    Paul

                    Originally posted by hongrn View Post
                    Heck, you're right Paul. I'm allowed one stupid mistake a year, am I not? All my built amps have soft starts, so I guess the sequence doesn't matter, hence MY confusion. Sorry abn1701.

                    Comment


                    • #11
                      Originally posted by Paul K. View Post
                      Yep, you're allowed one stupid mistake a year, and when you get to be my age, you're allowed to have numerous "senior moments" all year long, stupid or otherwise!
                      Paul
                      Yeah, but you know how badly it hurts being corrected by someone older than you are... (insert crying emoji here).
                      Some people are addicted to Vicodin. I'm addicted to speaker building.

                      The Chorales - Usher 8945A/Vifa XT25TG Build
                      ESP Project 101 Lateral MOSFET Amplifier
                      LM4780 Parallel Chipamp
                      Sonata Soundbar Project
                      The Renditions - Active/Passive Towers

                      Comment


                      • #12
                        This is strange.
                        I opened the amplifier and it has sof start .When power on the relay clicks and so when turned off. So the protection circuit appears to be working
                        I'm really confused why the amp thumps when turned off only.
                        Cheers

                        Comment


                        • #13
                          It is odd, the relay should disconnect the output devices before a turn off thump occurs.
                          www.billfitzmaurice.com
                          www.billfitzmaurice.info/forum

                          Comment


                          • #14
                            I have a carver amp that does that.....It started to happen after I changed some bulbs on the unit. After a google search looking at the service manual there is mention that there is some sort of relationship between the two. I'm considering placing the old bulbs back to confirm it :-)

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                            • #15
                              I have had a few amps that thumped when you turn them on but most of them didn't make any sound through the speakers . Only the amp it self made the sound .

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