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Sub Rumble/Noise but not ground or RCA's?

Old 01-27-2012, 04:19 AM
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Question Sub Rumble/Noise but not ground or RCA's?

I have a low rumble / noise like / grumble comming out of the RCA outputs of my ppi 4 channel amp.


I have a PPI 4240 4 channel amp feeding the main speakers. The main speakers sound fine. I have RCA output from the PPI going to a Phoenix gold octane amp to power a single sub.



There is no noise/rumble to the main car speakers, only on the RCA output that is feeding the the input of the sub amp.


My first Three thoughts were:

• Sub amp problem - not so, fed different RCA source to sub amp (from ipod) and it sounded fine. Used RCA's from PPI 4 channel amp, and there was the rumble again.

• Bad ground - not so, double and triple checked the grounds, it's solid.

• Bad RCA cable - not so, switched out the RCA' cable and the same prob.




So I'm thinking possibly it could be the RCA terminal output of the PPI amp, I'm about ready to crack it open but thought I would ask if anyone had any other ideas before I get jiggy on the innards of the ppi? Anything I should be looking for inside he ppi?

Last edited by Big_T; 01-27-2012 at 07:28 PM.
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Old 01-27-2012, 09:55 AM
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Is the RCA putput of the PPI a low-pass through, or a summed low pass output? I think you're on the right track, but you're likely going to have a bugger of a time identifying which component is causing trouble as the output is only "rumbly", so it's not as if you're going to see black marks or anything clearly fried.
My $.02
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Old 01-27-2012, 07:24 PM
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Originally Posted by audio1der View Post
Is the RCA putput of the PPI a low-pass through, or a summed low pass output? I think you're on the right track, but you're likely going to have a bugger of a time identifying which component is causing trouble as the output is only "rumbly", so it's not as if you're going to see black marks or anything clearly fried.
My $.02


Audio1der I appreciate your $.02!!

I'm not sure if it is a low-pass through, or a summed low pass output. Do you know how I can find out? all it says in the manual is


"Selectable FULL/HPF/LPF RCA Output"




Actually I found this pretty sweet site showing the interior.

http://amp-performance.de/408-Precis...r-PPI4240.html

Yep it looks just as daunting as I imagined. I mean I can see the RCA modules but I have a feeling it's goign to look nice and clean as you mentioned.

Could it be a failed capacitor not holding a load? I had a home audio selfpowered woofer that would rumble and make a grating noise when pushed and it was a capacitor. This may be different though.

Last edited by Big_T; 01-27-2012 at 07:26 PM.
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Old 01-27-2012, 08:57 PM
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Go buy some RCA Y cables and call it a day.

What audio1der said is true. Its most likely not going to be obvious what component of the filter is causing the bad RCA signal out. Hence my suggestion. You're most likely not going to be able to fix it, specifically without proper equipment. (Like an Oscilloscope to name one)

Last edited by Njord; 01-27-2012 at 09:04 PM.
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Old 01-28-2012, 10:18 AM
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^ Yep, as long as your PG amp has its own crossover you can use a pair of y-cables.
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Old 01-28-2012, 01:47 PM
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Yes this looks like the best overall solution thanks guys.

For my particular situation it won't work because I failed to mention in my orig post that am taking high level inputs to the PPI from the head unit speaker wires.

I know I know!! It's better to get the the direct RCA's but for this particular car (jag xj8) replacing the head unit is a can of worms I just don't have the time, or finances to get into. It would be easier to find a new (old) amp that takes high level inputs. I tried a high level input converter but it bled engine rpm related noise into the signal.

Last edited by Big_T; 01-28-2012 at 01:49 PM.
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Old 01-29-2012, 11:03 AM
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Keeping the factory deck is fine. I did on my last car and I am going to on my current car.

Maybe look into a Re-Q5. It's a great line level converter and has a summed sub out with level control. It also has a headphone jack input on it. Pretty nice piece for not a lot of bux.
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Old 01-31-2012, 07:16 PM
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Originally Posted by Dukk View Post
Keeping the factory deck is fine. I did on my last car and I am going to on my current car.

Maybe look into a Re-Q5. It's a great line level converter and has a summed sub out with level control. It also has a headphone jack input on it. Pretty nice piece for not a lot of bux.
Thanks for that Dukk, That's a pretty sweet piece of gear I never knew existed.
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Old 02-02-2012, 10:49 AM
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Even a high quality high-low level converter is not a lot of money, and do a good job without introducing alternator whine.(if the Re-Q5 is too much?)
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Old 02-02-2012, 02:35 PM
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For sure. The Re-Q5 isn't the cheapest LOC out there but it has so many neat features I recommend it to everyone who wants to keep their factory radio and doesn't want to pop for a full on processor like a BitOne, etc.
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