high pitched noise from system
Printed From: the12volt.com
Forum Name: Car Audio
Forum Discription: Car Stereos, Amplifiers, Crossovers, Processors, Speakers, Subwoofers, etc.
URL: https://www.the12volt.com/installbay/forum_posts.asp?tid=108575
Printed Date: April 29, 2024 at 3:49 PM
Topic: high pitched noise from system
Posted By: shagdrum
Subject: high pitched noise from system
Date Posted: October 31, 2008 at 6:58 PM
Here is what I am running (relevant to this issue) from newest component installed to oldest: an Alpine PDX 4.100 4 channel ampifier, a Clarion MAX685BT headunit, a pair of Alpine SPX-17REF in the doors and a pair of Alpine SPR-57c in the rear. The car is a 1996 Lincoln Mark VIII and the headunit was installed about 2 months ago, and the Amp about a 5 to 6 weeks ago. There is also a pair of subs run through aPDX 1.600 amp, but I don't think that is relevant to this issue. I recently started noticing a slight high pitch noise coming from the system. It didn't stay all the time but came on and off; intermitently. It did it on any input (DVD/CD, radio or Ipod)and it didn't matter if the car was running or not. It did not increase in pitch or intensity as the engine was reved, and it was present at all volume levels except zero. Thinking it might be the gains, I turned them all the way down and then listened for it. I couldn't hear it at any volume, though that could be because the signal wasn't boosted enough. I started adjusting the gains, and at even a very minor adjustment, the noise started coming back intermitently. It seemed more pronounced in the rear when adjusting the gains; as soon as the gain was moved it started making the noise. However, since the noise is so faint, it was hard to really tell. I am never hard on the system, and used a 1000Hz test tones to initially set the gains, as well as readjust them and check for the noise. I have checked all the connections on the headunit and the amps, and they are all fine. Any idea what it could be? What should be my next step(s) for troubleshooting this?
Replies:
Posted By: i am an idiot
Date Posted: October 31, 2008 at 7:02 PM
With the gains all the way down, are you able to reach your desired listening level? I know you will have to turn the volume of the radio to a higher level.
Posted By: shagdrum
Date Posted: October 31, 2008 at 7:04 PM
i am an idiot wrote:
With the gains all the way down, are you able to reach your desired listening level? I know you will have to turn the volume of the radio to a higher level.
Not anywhere near. At that level, the factory system would seem as loud if not louder, and probably as detailed...
Posted By: i am an idiot
Date Posted: November 01, 2008 at 4:05 PM
If the noise is not there at 0 but it is apparent at level 1, it can only be coming from the deck. I woldn't expect that from a Clarion deck, but it has to be coming from the deck.
Posted By: johnhansmann
Date Posted: November 01, 2008 at 4:26 PM
The noise your getting could be coming from having your power wire for your amp to close/same side of the car as your RCA wires. I had a high pitch noise in my stereo and i moved my RCA's to the otherside of the car and it solved the problem for me. Just a thought, you might be having the same problem.
Posted By: reax222
Date Posted: November 01, 2008 at 6:29 PM
It might also be worth looking at the alternator and battery.
Posted By: i am an idiot
Date Posted: November 01, 2008 at 6:39 PM
If it were the alternator, the battery or the patch cord being located next to the power wire, the noise would not go away when the deck was turned to 0.
Posted By: shagdrum
Date Posted: November 01, 2008 at 9:08 PM
RCA's are on the opposite side of the car from the power line and separated as much as possible at the point where they connect to the amp...
Posted By: shagdrum
Date Posted: November 01, 2008 at 10:19 PM
Here is what someone on another forum said about the 4 channel PDX amps... have a PDX2.150 and it is great. The 4.150 was terrible. It shares the same power supply for all four channels which resulted in a super high pitched noise that only some people could here when the car was not running. The 2.150 has the same power supply but, just for two channels. Great amp too. I also read something about an early batch of the PDX line having a defect (something to do with a circuit board or chip that was difficult to solider in the amp) that they fixed in newer runs. I don't know if that is related to the supposed power supply issue, but I think my Amp is one of the earlier PDX's (got it off ebay). Would that power supply thing in the amp be a possibility given the symptoms I described?
Posted By: i am an idiot
Date Posted: November 01, 2008 at 11:09 PM
Do you have a 1/8 inch to RCA cable so you can inject I-Pod audio directly into the amplifier?
It is Logic, the noise is not there at 0 but it is there at 1. The power supply of the amp can not tell when the radio comes off of mute. The alternator does not know when the radio comes off of mute. The only thing that knows when the mute circuit of the radio comes away from ground, is the radio.
Posted By: shagdrum
Date Posted: November 03, 2008 at 6:24 PM
Ok, I am pretty sure it is the 4 channel amp! Here's why... I went to reset the gains again with a 1000Hz test tone, but this time I unhooked all the RCA cables accept for the the "channel 1" (LF) cable. Then I disconnected the "channel 1" (LF) set of speaker wires. When I started playing the test tone, I could hear it coming through the rear speakers (though at somewhat less volume, but definately noticable and not at all faint). I disconnected the rear speaker wires (so only the RF speaker was connected), and didn't hear anything...until I had it and just below full volume ( "30" to be specific, and the volume goes from "0-33"). So, it looks to me like it is the amp. Would I be wrong in this diagnosis?
Posted By: i am an idiot
Date Posted: November 03, 2008 at 7:13 PM
Channel Separation
Also referred to as crosstalk. The amount of interference on one stereo channel caused by the leaking of the other stereo channel. The higher the rating in decibels (dB), the better the Channel Separation.
Posted By: shagdrum
Date Posted: November 03, 2008 at 11:01 PM
...so would I be correct in thinking it is the amp?
Posted By: i am an idiot
Date Posted: November 04, 2008 at 7:44 AM
It is normal for most amplifiers to have crosstalk, (this is what you are hearing) when driving one channel, the others will get signal from that channel and faintly play as you are describing. Perform the same test with someone elses amp, same results will be there. No I do not think it is your amplifier. Did you try the I-Pod directly into the amp yet?
Posted By: shagdrum
Date Posted: November 04, 2008 at 9:16 AM
I don't have an adaptor for the Ipod
Posted By: shagdrum
Date Posted: November 04, 2008 at 1:47 PM
The noise from the other speakers is not that faint... it is probably around 1/2 to 3/4 volume of what is (or should be) coming out of the speaker channel hooked up; and that is only the rear speakers. The other front speaker without a channel hooked up has no noise at all until very near full volume then there is a slight popping and it starts playing the signal at around the same volume as the rears.
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