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  1. #1

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    Default Amp discharge on power down.

    Trust this is the right section to post this in;
    I'm no tech & I need some guidance here. I picked up a PS Audio amp that seems to work fine but it discharges on shutdown & I'm concerned about the long term effect on my speakers, esp the tweeters as the discharge can be crackles as well as assorted pops & whistles. So the seller gave me 4 resistors & said I can use these to absorb the sound. I have a speaker selector switch & I'm going to connect these resistors - (2) Dale DCS 1/2, 1 0 mu 1 %, 7028 & (2) marked the same except 7026. So if I put a 7026 & a 7028 on left & 1 of each on the right, will that absorb the discharge from a 200 wpc amp? Speaker set "A" will be normal speakers, speaker set "B" will be the resistors. I would switch to set "B" before powering down. Sorry to be long winded but I don't want to make a potential problem an actual problem. Additionally, is it normal for an amp to discharge on shutdown? I haven't noticed it ever before on any of my equipment. TIA

  2. #2

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    I have an ATI amp that does the same thing. It is my understanding that some amps are designed this way to eliminate thump when powering on. Since the output capacitors are drained they must charge up when powered on eliminating the thump. Some amps have relays that open on shutdown, eliminating the drainage through the speakers. In my case as long as I turn off the pre or source first I get a silent shutdown, but if I just shut off the amp it will continue to play music for about 10-15 seconds before it dies off, giving pops and clicks for the last 3 to 4 seconds.
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  3. #3
    pepster
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    Pre have "mute"?
    Try muting it and then turn your amp off.

    I always turn my pre off last.

  4. #4

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    Thanks for the suggestions. As the pre is upstream of the amp (from the speakers), it has no effect on this phenomena. source to pre to amp to speakers. The discharge is from the amp & it is connected directly to the speakers so I can't fix this by powering down or muting the pre. I tried. I'm thinking there may be a defective protect relay in the amp. I'll need to read up on the amp & confirm it has one.

  5. #5
    pepster
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    Quote Originally Posted by Bob in WI View Post
    Thanks for the suggestions. As the pre is upstream of the amp (from the speakers), it has no effect on this phenomena. source to pre to amp to speakers. The discharge is from the amp & it is connected directly to the speakers so I can't fix this by powering down or muting the pre. I tried. I'm thinking there may be a defective protect relay in the amp. I'll need to read up on the amp & confirm it has one.
    You may have a bad resistor in your amp.
    Just a thought, and not 100% sure, but if you have major problems shutting down your amp, you got problems..................Just saying.

    Bleed resistor?

    My thoughts are the pre is is whats causing any shutdown noise.
    I have my doubts the actual amp is the cause.

    I would do a DMM test to check the amplifier before making any short term decisions on the amp.
    Could be, because the amp does not have NEAR as much gain as the preamp.

    And again.I am not sure, just a thought, nothing else.

    Hopefully someone with more "knowlege" than myself can chime in here!
    Last edited by pepster; 07-04-2013 at 01:24 AM.

  6. #6

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    Quote Originally Posted by Bob in WI View Post
    Trust this is the right section to post this in;
    I'm no tech & I need some guidance here. I picked up a PS Audio amp that seems to work fine but it discharges on shutdown & I'm concerned about the long term effect on my speakers, esp the tweeters as the discharge can be crackles as well as assorted pops & whistles. So the seller gave me 4 resistors & said I can use these to absorb the sound. I have a speaker selector switch & I'm going to connect these resistors - (2) Dale DCS 1/2, 1 0 mu 1 %, 7028 & (2) marked the same except 7026. So if I put a 7026 & a 7028 on left & 1 of each on the right, will that absorb the discharge from a 200 wpc amp? Speaker set "A" will be normal speakers, speaker set "B" will be the resistors. I would switch to set "B" before powering down. Sorry to be long winded but I don't want to make a potential problem an actual problem. Additionally, is it normal for an amp to discharge on shutdown? I haven't noticed it ever before on any of my equipment. TIA
    I think what you are hearing is just the sound of the power supply caps discharging. It would help to say what model amp, since PS Audio has made several 200 WPC models. If the amp has an output relay, it could be bad. If there is no output relay (for purist design reasons) the speakers are always connected to the output and the noise is just something you will have to learn to live with. Its audible, maybe annoying but harmless. Your speakers make louder sounds when you are watching a movie with loud explosions, gunshots, etc. or listening to music, not so ?
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  7. #7

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    PS Audio 200CX. Pre on or pre off makes no difference.

    " Its audible, maybe annoying but harmless" ....my only concern is for the speakers. I've heard that distortion blows more speakers than volume & the sounds is bugger makes on power down sure aren't musical. But if its not abnormal for this amp, I'm all good with it.

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    Seems odd to me. As I mentioned my amp dumps its stored energy thru the speakers but you cant hear unless I give it a signal to amplify. I can't imagine where those harmonics are being generated if not thru the input. Have you tried powering down with the interconnects disconnected from the amp? Perhaps the cables are picking up some emi/rfi. Or are you getting any ground loop hum in your system? My logic tells me the dc current should remain flat/silent unless its getting a signal from either input, ground, or emi/rfi. Im betting its not the amp its interference.

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    I can't say anything for certain but I've has 3 different pre's, & shut down the CD player before powering down the amp. The noises are not the same every time but tend to be a pop or thump followed by crackle or buzz sometimes for 10 seconds or more. Not usually hum, crosstalk, etc. The pre & turntable are grounded to the house wiring. I should prolly pick up new RCA jacks regardless, the one I have are pretty old (decades) altho they have been cleaned. I'm going to try with the input jacks disconnected next. That would surely eliminate or verify up stream sources.

  10. #10

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    +1 on what pester mentioned about turning off the preamp last. I've always followed the sequence of shutting off all power amps before turning off the preamp. I've got a couple of Soundcraftsmen power amps and they absolutely have___ to be turned off first before turning off the preamp , if not I'll fry some circuitry in them! There's a way to rewire them so I don't have to worry about this every time,but I'm not savvy on doing the work. I've noticed on my power amps when I power down the speakers will pop too, unless I use the speaker switch( A,B) to disconnect the signal to them.Obviously, I always mute the source on the preamp. It sounds like your PS Audio power amp may have a similar speaker selector switch to turn or off speaker set A or B or both?
    Last edited by Polkie2009; 07-04-2013 at 04:56 PM.

  11. #11

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    I bought a separate speaker selector switch for exactly that purpose. It gets installed tomorrow. I truly am not understanding how the pre that sits upstream on the amp - speaker connection can make any difference unless the source of the discharge is the pre itself & I'm fairly certain that is not the case. Regardless, its free to try so I will do that.

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    Quote Originally Posted by Polkie2009 View Post
    +1 on what pester mentioned...
    Freudian slip?

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    LOL!!!! Good catch BlueFox ! Sorry about that Pepster, it was my slip up.

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    B&K amps are famous for this. They do it while switching inputs too. I have been able to resolve this problem using a line conditioner on the amp. We use this guy, http://www.amazon.com/Panamax-M4300-...s=panamax+4300. Panamax 4300. We use another trick too but I cant remember it. I will post it as soon as I do remember.
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