Ok, heres the low down.... I recently (2 hours ago) installed 2 new JL Audio 5x7's to a JL Audio e1200 amp. I ran speaker wire through the doors directly to the amp. Power wire is installed, and ground is pretty good, considering the power coming from the amp. The problem is that when the speakers play, i get this low humming noise, and when my friend revs his engine (I did it in his truck) the humming from the speakers grows lowder. I rechecked all connections, no analog-signal wires are running next to the power or ground wire. All RCA connections are correct and complete. The only thing I can think of is finding a different ground, maybe the excess power is being pushed back through the RCAs, that had happened to a friend when he hooked up his subs/amp, but I never had it happen before when doing 5x7/amp. If you have any suggestions or ANYTHING, pleaaaaase oh please let me know HAPPY
Thanks tons,
-Sylver
Replies (6)
swez on 12/28/2003 07:35:50
Ahhhh, noise is the baine of all installers. Was there any noise in the system with the engine off, but when you fired it up, Viola... ALT whine? Our FAQ section has a few sub topics on same too.
There are a few basic things to check out first:
1. A solid ground to floor pan (bare metal) for HU & amp (without these firmly in place, noise is common... no harness grounds here)
2. Make sure you have the amp gains set to match the output of the HU... (if you have a 2.0 volt HU, set the gain at ~2 volts... not 250mV!) Most amp gains have a variable setting dial on them. They typically range from 1/4 volt (250mV is max gain setting) to 4.0 volts. Your 2.0 volt setting is usually close to midpoint on the gain dial(s).
If after checking these for correct install practices, the noise is still present, try shifting the RCA's a bit to see if that cures the problem. If the RCA's do come near the main power feed line, make sure they cross the power feed line at 90 degree angles. This minimizes noise transfer.
Worst case, may need to add a ground loop isolation transformer. This is an air core transformer that passes AC signals (via RCA cables) but blocks DC which can creat noise. Not always effective... but if the grounds and RCA wiring are not good, this may your last resort. Read this for clarification:
http://www.eatel.net/~amptech/elecdisc/glisoltr.htm
Swez
ttocs on 12/28/2003 10:45:07
audible tachometer...............
Sylver on 12/28/2003 11:48:51
Thanks for the help, it turned out that I had done it right, but the amp the guy gave me to put in that he had "sworn was in perfect working condition" was actually not in proper working condition. His RCA's are trying to pull power, and when we hooked it back up I smelled a burning from the amp, not good. He said that he smelled that all the time when he had it last hooked up, so I just took it out and sold him a new amp, put it in and it worked great. Thanks again for the help guys!!!
swez on 12/28/2003 12:00:33
Good nuff... "RCA's pulling power" ??? I don't get that part... RCA's carry low voltage audio signals from the source unit, back to the amp. They also provide a common ground reference between HU & amp(s) to help reject noise. They do not pull power at all, only feed what is present from source... back to a secondary device like an amp, signal processors and the like.
My guess, the magic smoke is from a filter or preamp circuit in this amp. Repairs are the cure after he tracks down what componets are in question in the amp...
Swez
cplkittle on 12/28/2003 15:24:21
off topic..
where did your medal go, swez?
ttocs on 12/28/2003 15:27:36
SWEZ GOT DEMOTED!!!!! Did you and walter have a falling out, or did you give it up for that hot singer like I was trying too?
I think he meant that he had a dc voltage on his rca's.
Thanks tons,
-Sylver
Replies (6)
swez on 12/28/2003 07:35:50
Ahhhh, noise is the baine of all installers. Was there any noise in the system with the engine off, but when you fired it up, Viola... ALT whine? Our FAQ section has a few sub topics on same too.
There are a few basic things to check out first:
1. A solid ground to floor pan (bare metal) for HU & amp (without these firmly in place, noise is common... no harness grounds here)
2. Make sure you have the amp gains set to match the output of the HU... (if you have a 2.0 volt HU, set the gain at ~2 volts... not 250mV!) Most amp gains have a variable setting dial on them. They typically range from 1/4 volt (250mV is max gain setting) to 4.0 volts. Your 2.0 volt setting is usually close to midpoint on the gain dial(s).
If after checking these for correct install practices, the noise is still present, try shifting the RCA's a bit to see if that cures the problem. If the RCA's do come near the main power feed line, make sure they cross the power feed line at 90 degree angles. This minimizes noise transfer.
Worst case, may need to add a ground loop isolation transformer. This is an air core transformer that passes AC signals (via RCA cables) but blocks DC which can creat noise. Not always effective... but if the grounds and RCA wiring are not good, this may your last resort. Read this for clarification:
http://www.eatel.net/~amptech/elecdisc/glisoltr.htm
Swez
ttocs on 12/28/2003 10:45:07
audible tachometer...............
Sylver on 12/28/2003 11:48:51
Thanks for the help, it turned out that I had done it right, but the amp the guy gave me to put in that he had "sworn was in perfect working condition" was actually not in proper working condition. His RCA's are trying to pull power, and when we hooked it back up I smelled a burning from the amp, not good. He said that he smelled that all the time when he had it last hooked up, so I just took it out and sold him a new amp, put it in and it worked great. Thanks again for the help guys!!!
swez on 12/28/2003 12:00:33
Good nuff... "RCA's pulling power" ??? I don't get that part... RCA's carry low voltage audio signals from the source unit, back to the amp. They also provide a common ground reference between HU & amp(s) to help reject noise. They do not pull power at all, only feed what is present from source... back to a secondary device like an amp, signal processors and the like.
My guess, the magic smoke is from a filter or preamp circuit in this amp. Repairs are the cure after he tracks down what componets are in question in the amp...
Swez
cplkittle on 12/28/2003 15:24:21
off topic..
where did your medal go, swez?
ttocs on 12/28/2003 15:27:36
SWEZ GOT DEMOTED!!!!! Did you and walter have a falling out, or did you give it up for that hot singer like I was trying too?
I think he meant that he had a dc voltage on his rca's.
Copyright ClubKnowledge 2009 * All Rights Reserved
