Ok, good to know. I had wondered if it had anything to do with this amp being injecting noise into the other amps of the system when not used with a ground loop isolator.
By bridging, and please bear with me, you mean simply soldering a wire between them and installing back in the car?
By bridging, and please bear with me, you mean simply soldering a wire between them and installing back in the car?
Yes.
Why can't you test it out of the car?
This amp has balanced inputs. It should not be causing noise in the system. I'm assuming that you're driving the other amps from the head unit and not the RCA outs from this amp.
What's the resistance from pin 5 that you used for ground and the RCA shields?
Why can't you test it out of the car?
This amp has balanced inputs. It should not be causing noise in the system. I'm assuming that you're driving the other amps from the head unit and not the RCA outs from this amp.
What's the resistance from pin 5 that you used for ground and the RCA shields?
I neglected to make any reference measurements before taking it out of the car and thought it would be easiest to compare in the car and to see if the same amount of gain gave the same amount of output from the sub.
Do I drive a signal into it, measure the voltage at the speaker terminals then install the bridge wire and do the same again looking for an increased voltage?
The resistance between pin 5 and the output RCA shields is very low, around the resistance of the leads plus a decimal point or two.
I am driving the other amps from the same head unit, the balanced inputs explains the infinite resistance between the RCA shields on the input ( I think) but it's very bizarre.
I took the whole relay/aux power panel out of the car to see if that was causing noise, nada. The two other amps, a Soundstream and and a Sony, are perfectly quiet on their own or in combination with any other sub amp I own; this JBL adds engine speed dependant whine whenever plugged in without a transformer based isolator.
Do I drive a signal into it, measure the voltage at the speaker terminals then install the bridge wire and do the same again looking for an increased voltage?
The resistance between pin 5 and the output RCA shields is very low, around the resistance of the leads plus a decimal point or two.
I am driving the other amps from the same head unit, the balanced inputs explains the infinite resistance between the RCA shields on the input ( I think) but it's very bizarre.
I took the whole relay/aux power panel out of the car to see if that was causing noise, nada. The two other amps, a Soundstream and and a Sony, are perfectly quiet on their own or in combination with any other sub amp I own; this JBL adds engine speed dependant whine whenever plugged in without a transformer based isolator.
At a low level (whatever is possible on the bench), you should be able to make/break the connection to see if the difference is significant.
Infinite resistance to ground is normal from the input shields.
0 ohms from ground to the output shields is normal.
Infinite resistance to ground is normal from the input shields.
0 ohms from ground to the output shields is normal.
The difference seems significant, with the jumper installed the output is 36V and without it's 30V.
Just to be clear, the input shields read infinite resistance both to ground and to each other.#
So if I have understood once more, installing that bridge defeats the remote bass knob circuit and I have my answer, being that if I do buy a bass knob I can turn the gain up a bit and probably get the headroom I wanted?
Just to be clear, the input shields read infinite resistance both to ground and to each other.#
So if I have understood once more, installing that bridge defeats the remote bass knob circuit and I have my answer, being that if I do buy a bass knob I can turn the gain up a bit and probably get the headroom I wanted?
Last edited:
With as much voltage as you have across the LED, I think the LDR/LCR should pass audio as well as the jumper. I have no proof of that.
I see, so in other words without replacing it there is no way to know definitively?
Would leaving the jumper in long term cause any harm?
I think I'll order a bass knob anyway but could test it in the car in the meanwhile if not.
this still ealves the issue of the whine which has me baffled, given that the balanced inputs make it impossible for this amp to be injecting noise into the head unit, what about it could possibly cause the noise in the other amps only when this one is connected?
I don't mind sending it away for repair if the possible causes are beyond my abilities, just curious as have never encountered this before, could a faulty LCR be behind it?
Would leaving the jumper in long term cause any harm?
I think I'll order a bass knob anyway but could test it in the car in the meanwhile if not.
this still ealves the issue of the whine which has me baffled, given that the balanced inputs make it impossible for this amp to be injecting noise into the head unit, what about it could possibly cause the noise in the other amps only when this one is connected?
I don't mind sending it away for repair if the possible causes are beyond my abilities, just curious as have never encountered this before, could a faulty LCR be behind it?
Replacing it may tell you if it's defective.
The jumper won't do any harm. It could cause a turn on/off noise.
Engine noise can be difficult to troubleshoot. Where are you getting the signal for it?
The engine noise isn't likely due to the LCR.
The jumper won't do any harm. It could cause a turn on/off noise.
Engine noise can be difficult to troubleshoot. Where are you getting the signal for it?
The engine noise isn't likely due to the LCR.
Ok, I’ll order the part and replace it too.
The signal comes directly from the head unit sub out pre out. The head unit is a pioneer, the rca have been checked, as has the head unit ground.
The signal comes directly from the head unit sub out pre out. The head unit is a pioneer, the rca have been checked, as has the head unit ground.