Solve my riddle - Stop the POP!

Discussion in 'Home Theater Projects' started by Doug Beavers, Mar 16, 2006.

  1. Doug Beavers

    Doug Beavers Auditioning

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    I have an interesting (frustrating) problem - hopefully someone can help. I have had my HT system for a 2 years now, and have been running my system off the amps in my Rotel RSX 1055 surround receiver, and it has performed well. I decided to add in an Adcom GFA 545 amp to power the front speakers. The performance improvement was noticable, but so was the problem. When I change sources on the reciever, from DVD to Tuner to Ipod -- "POP" comes through the speakers.

    It gets weirder, though. When I watch a DVD, the "pop" comes when I make a selection on the menu, or when a looping menu comes to the end of its loop. "Pop," and then the menu starts again. I love the sound of my system with the added oomph of the adcom amp, but this pop is driving me nuts! Can you help me stop the pop and keep the power? THANKS!

    System (in case it helps solve the problem): Rotel RSX1055 Surround processor, Adcom GFA 545 amp, B & W speakers (5), NHT W1 sub, X1 sub crossover, A1 sub amp, Pioneer Elite 45a Universal Player, Sony 34" Widescreen XBR TV, Scientific Atlanta Cable receiver, Panamax line conditioner/power strip.
    Doug Beavers
     
  2. Chu Gai

    Chu Gai Lead Actor

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    Was there also a 'pop' with just the receiver? Is it limited to just the front speakers, all of them, or just some of them?
     
  3. Doug Beavers

    Doug Beavers Auditioning

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    The pop started with the introduction of the amp. I suspect the sound is only coming from the front speakers, but I will have to check tomorrow to confirm.
     
  4. Chu Gai

    Chu Gai Lead Actor

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    Play around with it Doug. Also, for the hell of it, put the amp on the other speakers and see what happens. Maybe it happens to anything that's connected to the amp, maybe it's only one amp channel.
     
  5. Grant B

    Grant B Producer

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    I had that problem with a Carver Amp/ preamp many years ago.

    Is everything plugged into the power strip? Try going direct to the AC and see if it changes.
    It seems like a grounding problem. can you fun a wire from the case of the Rotel to the case of the amp?
     
  6. Doug Beavers

    Doug Beavers Auditioning

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    Well, the pop only comes from the front speakers. All of the components are plugged into the Panamax. When it started, I had things plugged into some less-than-high-grade power strips. Hoping it would fix the problem, I installed a 15 amp plug in the living room and the panamax power strip. When that didn't work I tried a few different grounding wires from each of the components to the grounding lug on the back of the panamax. No effect, except when I grounded the DVD player, which introduced a lovely interference pattern on the TV - NOT helping.

    I will try grounding from the receiver to the adcom today. Thanks for the help!

    Doug
     
  7. Doug Beavers

    Doug Beavers Auditioning

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    Tried grounding the amp to the receiver. No love. Wierd, huh? The riddle remains unsolved....

    Thanks for trying - I'm not giving up yet!

    Doug
     
  8. Andrew Pratt

    Andrew Pratt Producer

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    Unplug the coax cable from the Scientific Atlanta Cable receiver and see if you still have the problem when watching movies etc. My guess is that you've got a ground loop problem that's very likely from the cable feed. If that lowers or removes the pop altogether let us know and we'll see about fixing the problem. Some might suggest using a "cheater" plug as well but that's potentially very dangerous and really only masks the problem. Still its also a good test to see what the problem is.
     
  9. Doug Beavers

    Doug Beavers Auditioning

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    No luck with the cable in. Did not effect the pop.

    Doug
     
  10. Andrew Pratt

    Andrew Pratt Producer

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    Do you have any cheater plugs/adaptors that we could test with?
     
  11. Chu Gai

    Chu Gai Lead Actor

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    What happens when you don't plug the Adcom into the power strip but into the other outlet?
     
  12. Doug Beavers

    Doug Beavers Auditioning

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    A cheater plug takes the three prong plug to a two prong, right? Don't think I have one around here, but I will check tomorrow. I will try plugging the amp into the wall, and everything else into the power strip.

    Thanks! I'll let you know what happens.

    D
     
  13. Doug Beavers

    Doug Beavers Auditioning

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    Tried pluggin the amp into the the wall outlet and the rest of the equipment into the panamax. Still poppin'. I will hunt down a cheater plug, but I don't intend to override the ground for any longer than to see if it makes a difference. Not interested in taking any risks with electricity, fire, etc.

    D
     
  14. DaveHo

    DaveHo Supporting Actor

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    I suspect the real issue is with your Rotel receiver, not the amp. I used to have an Adcom GFA-535 & a GTP-500. The GTP-500 had two outputs one marked "lab" and another marked "normal". I remember something in the manual about using the "lab" output if the amp could support being direct coupled. Something that was true of the Adcom amp & not of all others. I suspect your receiver is momentarily shorting the output when changing processing modes, which in turn is causing the Adcom amp to generate a pop. Apparently the Rotel's own amps use a different design which accounts for this. This is all speculation of course and I may have some of the terminology wrong. Have you tried any other amps?

    -Dave
     
  15. Chu Gai

    Chu Gai Lead Actor

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    Let's see if I can summarize the situation as it stands right now.

    1) Your existing setup, minus the amp, worked fine. No pops no matter what you did but you wanted to add a separate amp so you bought a used amp.

    2) Once you added the amp to the front channels you noticed several problems. Among those being a series of pops and ticks that occurred only to the front channels.

    3) Moving the amp to the other channels still resulted in pops from the front channel. Did you actually move the amp to the other channels?

    4) No matter how you hook up things with the amp, disconnect the cable, run additional grounds here and there still there are ticks and pops.

    Probably the last thing I'd try is to confirm #3 above and then just remove the amp completely from system to see if there are problems that weren't there before. If there are, then DaveHo's thoughts sound reasonable.

    As a final thought, you are using shielded cables connecting the amp to your receiver, right?
     
  16. Kevin T

    Kevin T Screenwriter

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    are you using optical or coax from your dvd player to receiver? perhaps your receiver is losing it's "lock" on the digital signal and the corresponding pop you hear is it re-acquiring the signal. without hearing the pop, i obviously couldn't be sure. for shits and giggles try a different type digital cable than what you already use.

    kevin t
     
  17. Doug Beavers

    Doug Beavers Auditioning

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    Thanks for the great ideas guys - I will test your ideas tonight. In response to Chu Gai:

    1) Everything was fine before the amp.

    2) When I introduced the Adcom (from another system I had) it performed well with the noticable exception of popping when changing menu selections on DVDs, and when changing between some sources on the Receiver. Otherwise, no problems.

    3) I will try running the amp through different channels, and I will try a different digital link tonight. If I can find a cheater plug in the house, I will give that a shot too.

    4) The cables came with the amp, but I also tried some different ones, and they did not help.

    5) If none of that makes a difference I will pull the amp out, to confirm that the pop stops when the amp is gone.

    Doug
     
  18. Chu Gai

    Chu Gai Lead Actor

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    If it turns out it is the amp Doug, you can give Adcom a call and tell them about it as well as all the things you tried. There might be something simple. I also have one last idea with absolutely no guarantee that it'll work. Although you'll have to spend money and time, you can get your money back. The time...well, that'a another story.

    The thing is, we really don't know how the pops are making their way into the amp. I suspect that it's not through the power cord but through your interconnects. If that's the case, then maybe a product called the EbTech Hum Eliminator might do the trick. It's available at a variety of pro audio shops. If you look up 'Guitar Center', you'll probably find that there's one pretty close to where you live. Give them a call to check on availability and try this. The 10 second explanation of this product is that it sits between your amp and preamp. It breaks the ground with essentially no degradation in signal quality. I believe it does this via the use of isolation transformers. Jensen also sells these but they're much pricier. You might also be able to find a similar product from Radio Shack but I think its frequency response isn't out to 20 kHz. Guitar Center has a pretty good return policy (confirm this on the product) so if it doesn't work, you're out time.
     
  19. Brian Osborne

    Brian Osborne Stunt Coordinator

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    I think Kevin is on the right track. I have the same problem. Happens when i change inputs on the reciever, when making selections on menues from digital sources, and when my DVD player switches layers on DVDs. I introduced all new equipment with I did it so I can't place blame on one particular peice.
    I will try changing the audio conection type. Strange thing, it didn't do this when I had my DVD player hooked up via HDMI, but it does via optical.
     
  20. Doug Beavers

    Doug Beavers Auditioning

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    Believe it or not - I finally came up with a set up that eliminates the pop! I have no earthly idea what the problem was, but mayb e somebody will get it when I explain what I did.

    Previously, I had run the pre-outs for the front L & R signal out of the Receiver and directly into the Adcom L & R inputs. This was followed by all the popping. Today, I finally had a chance to spend a few hours with it. I took the amp out and the noise disappeared. Then, I ran the Front L & R pre-outs from the rotel into the NHT X1 crossover input, then brought the hi pass output back into the Adcom inputs, and the sub outs into the sub input on the A1 (I only have 1 A1 amp and one w1 sub)

    Voila - The pop stopped! Thanks for your help folks!

    Doug Beavers
     

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