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Receivers, Amps, and Processors

jsbenson's Avatar jsbenson
02:27 PM Liked: 10
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I have a paradigm sub and the amp died. Unfortunately it's out of warranty so I looked for an alternative power method. I had an extra Denon receiver so I used that exclusively to power the subwoofer. But I'm getting some unexplained hiss and I haven't been able to pinpoint the problem.

Main receiver - Denon AVR-1912
--subwoofer preamp out to
Subwoofer receiver - Denon AVR-3806 Right-channel in
--subwoofer receiver set to "direct in" and right speaker channel to
Paradigm subwoofer


I have tried lowering the volume on the sub pre-amp and increasing the sub level output on the main amp (and visa-versa) but I still get very noticeable hiss.

Here are other things I have tried:
Changing speaker wire and rca cable
Checking other inputs on sub amp...hiss only occurs on whatever input is receiving the subwoofer signal
EQing all the high frequencies down on the subwoofer amp
Hiss increases with either sub amp volume level or sub pre-out

Does anyone have a clue what this might be? Is there an alternate setup I could use to avoid this?

Thanks
JHAz's Avatar JHAz
02:51 PM Liked: 167
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Generally hiss, at least as I think of it, should be filtered out by the low pass to the sub, presumably fromvthe main receiver's basd managrment. What is your sub crosdover frequency? But if the receiver channel in the second receiver has a bunch of intrinsic noise the first receiver's crossover won't eliminate it.
jsbenson's Avatar jsbenson
02:58 PM Liked: 10
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Quote:
Originally Posted by JHAz View Post
Generally hiss, at least as I think of it, should be filtered out by the low pass to the sub, presumably fromvthe main receiver's basd managrment. What is your sub crosdover frequency? But if the receiver channel in the second receiver has a bunch of intrinsic noise the first receiver's crossover won't eliminate it.
That's correct, and the filter is set that way. LFE+Main crossover is set to 80hz, which is what will be output go to the main receiver's sub preamp out, which should be the only signal sent to the subwoofer amp.

I also tried cutting all the frequencies above 125hz on the subwoofer amp and it makes no difference. If I change the input on the subwoofer amp to another input then the hiss is gone. I plugged my ipod into one of the inputs and the output to the sub was clean on that input.
jsbenson's Avatar jsbenson
04:29 PM Liked: 10
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I wonder if I go from my SW preamp to one of the inputs on the same amp (like CD right channel) and then assign CD to zone-2 and just use zone-2 for the subwoofer.

Anyone see any problems with this?
jsbenson's Avatar jsbenson
04:51 PM Liked: 10
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I started messing around with my signals and figured this out:

If I play a movie, there's no hiss. My movies are all dolby digital
When I'd stop the movie on my HTPC the his would start up again.

If I play a music video I get hiss. Figured out my music vids are PCM

Switched to directv and got hiss. It was in PCM mode so I switched to dolby digital and the hiss went away.

So I guess the real problem is that I'm getting hiss only on PCM and only in my subwoofer. Does anyone know why I'd get hiss in my sub with PCM?
jsbenson's Avatar jsbenson
05:22 PM Liked: 10
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Quote:
Originally Posted by jsbenson View Post
I started messing around with my signals and figured this out:

If I play a movie, there's no hiss. My movies are all dolby digital
When I'd stop the movie on my HTPC the his would start up again.

If I play a music video I get hiss. Figured out my music vids are PCM

Switched to directv and got hiss. It was in PCM mode so I switched to dolby digital and the hiss went away.

So I guess the real problem is that I'm getting hiss only on PCM and only in my subwoofer. Does anyone know why I'd get hiss in my sub with PCM?
It seems like Netflix and everything else on my HTPC (including WMC with exception of movies) uses PCM even though I set my audio device to output using dolby digital. My audio device is a realtek HD audio device.

Does anyone have any ideas on this or should I start a new thread in home theater PCs?
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