My old headunit had the LCD/driver failed.
I swapped the headunit out for an Eclipse one, just three wires, ground, constant power, accessories power.
Nothing else in the setup changed.
First time I turned it up loud, as I turned it down, there was still "bass" coming from the subs.
At volume 0, the headunit actually mutes the output, and the "bass stopped" turn the volume back up one notch, and I get near full volume, single frequency tone...
Does this sound like motorboating? and why? whats changed that its happening now?!
I swapped the headunit out for an Eclipse one, just three wires, ground, constant power, accessories power.
Nothing else in the setup changed.
First time I turned it up loud, as I turned it down, there was still "bass" coming from the subs.
At volume 0, the headunit actually mutes the output, and the "bass stopped" turn the volume back up one notch, and I get near full volume, single frequency tone...
Does this sound like motorboating? and why? whats changed that its happening now?!
wiring is like this:
I'm wondering if possibly flat batteries might have increased the chances of it happening...
The sub stage amplifier actually doesn't have its RCA inputs tied to battery ground, they're isolated, so this isn't a ground loop.
edit: I grounded the headunit to the 4ga cable that runs to the front stage amp, as a 50mv difference in ground potential was causing the sub amplifiers to go into protect with the old headunit...
I'm wondering if possibly flat batteries might have increased the chances of it happening...
The sub stage amplifier actually doesn't have its RCA inputs tied to battery ground, they're isolated, so this isn't a ground loop.
edit: I grounded the headunit to the 4ga cable that runs to the front stage amp, as a 50mv difference in ground potential was causing the sub amplifiers to go into protect with the old headunit...
Did you check the shield ground on the head unit to confirm that they were 0v to the case of the head unit?
Did you try one of the other sets of RCA outputs to drive the sub amps?
Did you try one of the other sets of RCA outputs to drive the sub amps?
0v, or 0ohm? 😉 I'll do that later today...
I can't use the other rca cables, as the front stage amp is mounted under the front passenger seat.. Unless you meant to simply swap the rca cables on the headunit?
I only turned it up once, and it did it, so its not really something I want to do again, as I figure I'm risking damaging the subs...
Plus, its too loud to turn it up at home...
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went for a drive today, turned the stereo on... "brrrrrr"
turn the volume down to 0, once again, the sound stops....
so when I got home, I put the scope on the sub amplifiers output, with the subs disconnected....
wouldn't motorboat... tried 3 or 4 times, wouldn't happen....
I actually think its low, although it sounded in the audible range, it may have been lower, and the subs were only saved by the sub sonic filter....
turn the volume down to 0, once again, the sound stops....
so when I got home, I put the scope on the sub amplifiers output, with the subs disconnected....
wouldn't motorboat... tried 3 or 4 times, wouldn't happen....
I actually think its low, although it sounded in the audible range, it may have been lower, and the subs were only saved by the sub sonic filter....
I'll have a look at it later this week once the weather has cooled down.
Its not impossible that the replacement headunit has a grounding issue, or a blown fuse/trace on the rca ground...
Its not impossible that the replacement headunit has a grounding issue, or a blown fuse/trace on the rca ground...
I discovered that if I moved the rca cables near the amp, or played with the rca plugs, I got what could only be described as feedback... higher pitched than the original motorboating I heard... I'd also turned the gain down....
I also have this weird tone, very quite, that will increase in pitch till its inaudible through the subs, then at some point, start decreasing in pitch back down to the subsonic range, and then it repeats... but this is very quiet...
tomorrow, I'll have another look at it!
I also have this weird tone, very quite, that will increase in pitch till its inaudible through the subs, then at some point, start decreasing in pitch back down to the subsonic range, and then it repeats... but this is very quiet...
tomorrow, I'll have another look at it!
I swapped the rca cable today.
What I didn't realise, was that the old cable didn't use the shield as the ground...
Although it had an aluminium foil shield, it wasn't actually grounded!?!
I think the old cable had become microphonic...
Another thing, because the shield wasn't used as ground, instead it has a twisted pair of wired per channel... this meant that the ground wire measured about 0.7ohm! whereas, on the new cable, the ground/shield measures only 0.03ohm... much better!
No more "feedback" not sure about motorboating yet!
What I didn't realise, was that the old cable didn't use the shield as the ground...
Although it had an aluminium foil shield, it wasn't actually grounded!?!
I think the old cable had become microphonic...
Another thing, because the shield wasn't used as ground, instead it has a twisted pair of wired per channel... this meant that the ground wire measured about 0.7ohm! whereas, on the new cable, the ground/shield measures only 0.03ohm... much better!
No more "feedback" not sure about motorboating yet!
Some cables that use a twisted pair for each channel have a shield that's only connected to the shield ground on one end. That end is connected to the source unit.
this was not connected at either end.
I was able to move the cable and kill the "feedback" noise completely, I believe this was because the shield was being connected.
The resistance on the ground wire wasn't helping at all either, and may have been the cause of the motorboating.
We shall see! I was made redundant a week ago, so haven't had to drive the car much, if at all...
I was able to move the cable and kill the "feedback" noise completely, I believe this was because the shield was being connected.
The resistance on the ground wire wasn't helping at all either, and may have been the cause of the motorboating.
We shall see! I was made redundant a week ago, so haven't had to drive the car much, if at all...
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