problem with bass level fluctuations

[BTE]

Here is my problem, I will be driving along listening to music and everything sounds great, but then, the bass level drops like I turned it down. It will come back on its own, but it is random. Basically it's like if I had my bass set at 10, it will play at 10 for a while then drop to 5, then back to 10, then to 5 and so on. But always to the same two levels it seems. It started out happening less frequently but now it happens all of the time, even on short drives.

My set-up is as follows:

Alpine 9883

Alpine PDX-5

JL 10W3V3

Alpine SPX 17REF components

Everything is about a year old minus the head unit, which is 6 years old.

Is it possible the sub pre outs are loosing connection? It doesn't appear to be the amp going into protection mode because it doesn't turn the light red and it doesn't seem to affect the other speakers. The tech at Alpine only suggested sending it in to be tested.

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[thevic24 5,000+ posts]

Are you using a remote bass level control?

You can check the input jacks by trying to move them while the amp is playing to see if you can duplicate the problem.

 

[goingdef 10+ year member]

I had something like that once, it was a bad rca connection at the amp if you have it turned down low unplug one and then the other it should get half as loud each time you unplug one but if it stops playing on one you know which is bad.

 

[BTE]

No remote bass control. I will start checking the RCA's.

 

[West]

Sometimes the RCA covers (between the cord and the pin) have to be turned to get a good ground. Not sure what brand he is using. I had the same thing happen last week with my front left channel.

 

[keep_hope_alive Premium Member]

voltage drop will do that as well. install a volt meter in the dash (even a cig lighter one) and see if the battery voltage drops when that happens.

loose grounds can cause this as well.

 

[BTE]

I tried what goingdef suggested. I unplugged one and nothing happened, then unplugged the other and lost the signal. So I assume I am looking at an RCA problem? Or can a bad preout translate through an RCA making it look like the problem? I will pull the headunit and try a different set of RCA's to see what happens.

I will also check the RCA covers.

The volts do not look like they drop when this happens, but I am using the factory gauge.

 

[BTE]

OK, I installed a different set of RCA's and turned on the stereo. I pulled each RCA plug one at a time and both times the bass level dropped, but it didn't cut out.

So it seemed like the old RCA's were bad. I then re-connected the old ones to see if the problem followed the cables, and I got the same result as I did with the new cables. Now I am more confused because it could still be the old cables with an intermittent problem or the preouts.

 

[keep_hope_alive Premium Member]

ditch the old cables. they can have intermittent connections. run the new ones. if it still acts up, then it could be the inputs on the amp.

 

[quackhead 10+ year member]

voltage drop will do that as well. install a volt meter in the dash (even a cig lighter one) and see if the battery voltage drops when that happens.
loose grounds can cause this as well.

loose grounds or loose connections on the power wire, check the fuse near the battery. Go over every connection with a DMM and check for voltage irregularities.

Check the amp connections and make sure there is not any stray single strands of wire at the power/remote connections and the speaker connections that may be touching something they shouldn't.

 

[BTE]

I will go over and double check everything. Thanks for all the information, you all have been a ton of help!