Ground Loop?

venomclan
venomclan Posts: 2,467
edited November 2005 in 2 Channel Audio
Hi Guys,
I think I may have a ground loop problem. I recently got a Krell Kav 250a and 250p amp and preamp. When I turn on the 2-channel amp, there is a thump sent through my speakers for a second. What do you think will cause this thump. I had previously had an h/k pa5800 amp and Outlaw Mblocks hooked up with no problems. Is it a ground loop problem? I had heard of others with a similar problem but I don not recall the solution. Any recommendations appreciated. Thanks.
Jeremy
Post edited by venomclan on
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  • F1nut
    F1nut Posts: 50,551
    edited April 2004
    A ground loop (hum) is an entirely different thing, you don't have that problem. Try doing this, turn on the amp first, wait a minute and then turn on your pre amp. When you turn things off, turn the pre amp off first, then the amp. That should solve the problem.
    Political Correctness'.........defined

    "A doctrine fostered by a delusional, illogical minority and rabidly promoted by an unscrupulous mainstream media, which holds forth the proposition that it is entirely possible to pick up a t-u-r-d by the clean end."

    President of Club Polk

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  • gidrah
    gidrah Posts: 3,049
    edited April 2004
    Agreed. This is not a ground loop problem. I have an integrated that thumps on power-up. I make sure to turn the speaker switch to "off" before powering on.
    Make it Funky! :)
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  • steveinaz
    steveinaz Posts: 19,538
    edited April 2004
    Many amps have this "thump" you're hearing at power-up, most notably Soundcraftsmen. Perfectly normal. Just stay in the habit of turning your volume all the way down after turning off your system. It's automatic for me as I had Soundcraftsmen amps for 14 yrs.
    Source: Bluesound Node 2i - Preamp/DAC: Benchmark DAC2 DX - Amp: Parasound Halo A21 - Speakers: MartinLogan Motion 60XTi - Shop Rig: Yamaha A-S501 Integrated - Shop Spkrs: Elac Debut 2.0 B5.2
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  • venomclan
    venomclan Posts: 2,467
    edited April 2004
    Hi Guys,
    Thanks for the advise. I have tried a few times to power on the amp first, the speakers thump every time no matter which order I power up. I spoke to Krell and they said it was normal. I am not the concerned with it just as long as it cannot do any damage to my b&w's. Thanks again guys for the input.
    Best Regards,
    Jeremy
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  • steveinaz
    steveinaz Posts: 19,538
    edited April 2004
    The amp will thump each and every time regardless of your "turn-on" sequence; it's a function of the amplifier.
    Source: Bluesound Node 2i - Preamp/DAC: Benchmark DAC2 DX - Amp: Parasound Halo A21 - Speakers: MartinLogan Motion 60XTi - Shop Rig: Yamaha A-S501 Integrated - Shop Spkrs: Elac Debut 2.0 B5.2
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  • tryrrthg
    tryrrthg Posts: 1,896
    edited April 2004
    This happens with my amp also, you can just leave you amp on all the time. I've read that you should just leave it on, especially if you use it everyday...
    Sony KDL-40V2500 HDTV, Rotel RSX-1067 Receiver, Sony BDP-S550 Blu-ray, Slim Devices Squeezebox, Polk RTi6, CSi3 & R15, DIY sub with Atlas 15
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  • venomclan
    venomclan Posts: 2,467
    edited April 2004
    Hi Guys,
    I have heard form many people that leaving the amp on all the time is good. Does an amp eat a lot of electricity when on, but not receiving a signal? My Krell 250a does get warm when left on and so does my preamp 250p. Are there any drawback to leaving the amp on? fire hazards? anything?
    Regards,
    Jeremy
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  • steveinaz
    steveinaz Posts: 19,538
    edited April 2004
    I guess the only drawbacks would be an elevated electric bill and maybe excessive heat. I personally don't do it.
    Source: Bluesound Node 2i - Preamp/DAC: Benchmark DAC2 DX - Amp: Parasound Halo A21 - Speakers: MartinLogan Motion 60XTi - Shop Rig: Yamaha A-S501 Integrated - Shop Spkrs: Elac Debut 2.0 B5.2
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  • rlw
    rlw Posts: 231
    edited April 2004
    Originally posted by venomclan
    [snip, snip]
    Are there any drawback to leaving the amp on? fire hazards? anything?
    Regards,
    Jeremy

    Yes. Fire hazard is one of them; it's conceivable that an amp can malfunction and start a fire if left on - and if memory serves me correctly, I've read about it happening to at least one person. Another drawback is that leaving the amp on, and drawing current, keeps it warm - - which dries out the capacitors quicker.

    With that said, I leave my amp on quite a bit - I like to fire it up on Thursday, and let it run through the weekend. I find that by Saturday, it's sounding very relaxed.
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  • venomclan
    venomclan Posts: 2,467
    edited April 2004
    Hi Guys,
    Thanks for the info. Anonymouse you are 100% right. I spoke with Krell and they said my amp has no relay, but also to not leave it on all the time because of the heat it produces. My Krell 250a is rated at 250 watts(8ohm) and 500 watts (4ohm), I am using B&W CDM7NT's for my mains and they are 8ohm speakers rated to handle 150 watts. I hope the power of the amp is not too much. I have heard that Krell power ratings are often underrated, and that my amp might be pushing more power than thought.

    I am curious to know at start-up how much power is behind the "thump". Amps usually do not need to output the majority of their power at low volumes or only if there is a sudden need, like an explosion in a movie. Does anyone know how much output the amp puts out when switched on?
    Thanks,
    Jeremy
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  • steveinaz
    steveinaz Posts: 19,538
    edited April 2004
    Don't sweat it brother, just get in the habit of "zeroing" your volume knob after shutdown...

    My Soundcraftsmen manual assured me that the thump was both normal and harmless.
    Source: Bluesound Node 2i - Preamp/DAC: Benchmark DAC2 DX - Amp: Parasound Halo A21 - Speakers: MartinLogan Motion 60XTi - Shop Rig: Yamaha A-S501 Integrated - Shop Spkrs: Elac Debut 2.0 B5.2
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  • HBombToo
    HBombToo Posts: 5,256
    edited April 2004
    Originally posted by venomclan
    Hi Guys,
    Does an amp eat a lot of electricity when on, but not receiving a signal? Regards,
    Jeremy

    My amp eats 1 amp while idle.:D

    Outlaw 770 with massive torroids and caps and at 7 channels what can 1 expect.

    HBomb
    ***WAREMTAE***
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  • polkatese
    polkatese Posts: 6,767
    edited November 2005
    I am resurrecting this thread, since my new power amp exhibits the "thumps", since it doesn't employ any muting capacitors to filter, during power on/off.

    I am curious if there is documented case(s) in which these thumps cause damage to speakers? annoying? yes, but I can live with that. Turning down the volume to minimum doesn't make it dissapear, and having 7 speakers thumps simultaneously is a bit nerve wrecking..
    I am sorry, I have no opinion on the matter. I am sure you do. So, don't mind me, I just want to talk audio and pie.
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  • phoneisbusy
    phoneisbusy Posts: 867
    edited November 2005
    The only time I've heard of power on thumps causing damage is in the case of active speakers where there is little or nothing between the amp and the tweeters. Thumps tend to be lower frequency and sending them to an unprotected tweeter will likely cause damage. Speakers with passive crossovers will filter the thump out to the tweeters.

    regards

    Dave
    Time is the best teacher. Unfortunately it kills all its students.
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  • McLoki
    McLoki Posts: 5,231
    edited November 2005
    My amp thumps on power down to my LSiC, sub, and 4 LSi7's. The amp is much stronger than the speakers are rated for and it does not appear to hurt them in the least. I have not measured the DB of the thump when it turns off but I bet it is about 80db and that should be under 1 watt of power running to them.

    It should'nt be a problem.

    Michael
    Mains.............Polk LSi15 (Cherry)
    Center............Polk LSiC (Crossover upgraded)
    Surrounds.......Polk LSi7 (Gloss Black - wood sides removed and crossovers upgraded)
    Subwoofers.....SVS 25-31 CS+ and PC+ (both 20hz tune)
    Pre\Pro...........NAD T163 (Modded with LM4562 opamps)
    Amplifier.........Cinepro 3k6 (6-channel, 500wpc@4ohms)
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  • polkatese
    polkatese Posts: 6,767
    edited November 2005
    thanks for the info, guys.
    I am sorry, I have no opinion on the matter. I am sure you do. So, don't mind me, I just want to talk audio and pie.
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  • steveinaz
    steveinaz Posts: 19,538
    edited November 2005
    Won't hurt a thing, relax bubba.
    Source: Bluesound Node 2i - Preamp/DAC: Benchmark DAC2 DX - Amp: Parasound Halo A21 - Speakers: MartinLogan Motion 60XTi - Shop Rig: Yamaha A-S501 Integrated - Shop Spkrs: Elac Debut 2.0 B5.2
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