Hi,
I hope this is a good place to ask.
I have a '99 Range Rover, that stock came with an Alpine head unit and a separate amp that drives the speakers.
For this reason I've been putting off getting a new head unit, as one with an unamplified output seems to be rather hard to find, especially reasonably priced.
Recently I came across this product from InCarTek, that bypasses the amplified speaker output, and plugs them into the head unit's pre-amp output. Great!
So yesterday I tried connecting everything, and while it works fine, there is a hell of a noise in the speakers. A bit of debugging later showed that this only occurs when nothing is plugged into the head unit's speaker plug, even when the pre-amp plugs aren't even connected.
This noise is gone if I plug directly into the speaker output, but then there's the dual-amp hum, and barely any volume adjustability that I wanted to prevent in the first place.
It seems to me the head unit is kicking out a bunch of noise in the power wires if there is no load on the speaker output.
Does anyone know of a solution to this? I've been trying to do some googling, but not getting many answers. A simple solution seems to be a dummy load, but a 4-8 Ohm 70W resistor is going to be a beefy chonker putting out lots of heat.
Or maybe a recommendation for a head unit that either doesn't have amplified outputs, or where they can be turned off (preferably reasonably priced...)?
Thanks in advance for the advice.
I hope this is a good place to ask.
I have a '99 Range Rover, that stock came with an Alpine head unit and a separate amp that drives the speakers.
For this reason I've been putting off getting a new head unit, as one with an unamplified output seems to be rather hard to find, especially reasonably priced.
Recently I came across this product from InCarTek, that bypasses the amplified speaker output, and plugs them into the head unit's pre-amp output. Great!
So yesterday I tried connecting everything, and while it works fine, there is a hell of a noise in the speakers. A bit of debugging later showed that this only occurs when nothing is plugged into the head unit's speaker plug, even when the pre-amp plugs aren't even connected.
This noise is gone if I plug directly into the speaker output, but then there's the dual-amp hum, and barely any volume adjustability that I wanted to prevent in the first place.
It seems to me the head unit is kicking out a bunch of noise in the power wires if there is no load on the speaker output.
Does anyone know of a solution to this? I've been trying to do some googling, but not getting many answers. A simple solution seems to be a dummy load, but a 4-8 Ohm 70W resistor is going to be a beefy chonker putting out lots of heat.
Or maybe a recommendation for a head unit that either doesn't have amplified outputs, or where they can be turned off (preferably reasonably priced...)?
Thanks in advance for the advice.
I don't understand exactly what you have but an aftermarket head unit will be fine if you use the preamp output only. There's really no reason to have the ability to turn the internal amplifier off.
Can you post a diagram of what you have in both wiring scenarios?
Can you post a diagram of what you have in both wiring scenarios?
Hi Perry,
Thanks for your answer. I tried making a quick diagram:
I hope that's clear enough.
I also got a reply from InCarTech, they recommend (yet another) adapter to suppress the ground loop. But that somewhat defeats their original adapter that gets the unamplified output from the head unit from the RCA jacks...
Thanks for your answer. I tried making a quick diagram:
I hope that's clear enough.
I also got a reply from InCarTech, they recommend (yet another) adapter to suppress the ground loop. But that somewhat defeats their original adapter that gets the unamplified output from the head unit from the RCA jacks...
I'm not sure why you want to avoid using the speaker level output. The newer amplifiers ICs produce a very good quality signal.
How are you connecting the pioneer speaker level signal to the OEM amplifiers? Are you using an adapter plug of some sort or are you using some other method?
How are you connecting the pioneer speaker level signal to the OEM amplifiers? Are you using an adapter plug of some sort or are you using some other method?
Mostly because there's then two amplifiers in series, and the volume adjustment on the head unit barely goes to 3 before it becomes unbearably loud.
As said, an adapter from InCarTek: Range Rover P38 VOGUE (99-02) - InCarTec
Very basic, and they're now trying to sell me yet another adapter to get rid of the ground loop. But I'm not convinced that's going to help anything, as I get the buzz without any speakers connected as well!
Can you return the adapter you have now?
I don't know what their ground loop isolator is. A decent line output converter will have an internal load (not really necessary), transformers to break ground loops and a level control for the preamp output. Examples can be seen on the following page:
Line Output Converters
I don't know what the OEM amplifiers need as a signal. Some use a near speaker level balanced signal. If the OEM amps need a balanced signal, a ground loop isolator may be the solution. Did they say you needed both the adapter you have now AND a ground loop isolator? More information on GLIs:
Ground Loop Isolators
Could you drive a test tone into the the head unit and measure the signal out of the head unit at full volume?A 60Hz would probably be best. You'd measure across the two wires that drive the OEM amplifier.
I don't know what their ground loop isolator is. A decent line output converter will have an internal load (not really necessary), transformers to break ground loops and a level control for the preamp output. Examples can be seen on the following page:
Line Output Converters
I don't know what the OEM amplifiers need as a signal. Some use a near speaker level balanced signal. If the OEM amps need a balanced signal, a ground loop isolator may be the solution. Did they say you needed both the adapter you have now AND a ground loop isolator? More information on GLIs:
Ground Loop Isolators
Could you drive a test tone into the the head unit and measure the signal out of the head unit at full volume?A 60Hz would probably be best. You'd measure across the two wires that drive the OEM amplifier.
Sorry for the late reply, had been a bit busy dealing with other things.
Dug into it again this weekend. Traced a bunch of wiring and found some issues (rear speakers not connected in adapter, amp in door corroded, bass speaker in LH door broken), but none of it solved the buzz.
Just powering the door amps without the rest of the wiring connected is enough to get the buzz - it seems like they need a strong enough signal to get over it.
I've now wired it in so the adapter does the steering wheel controls (works fine), and the speakers get driven by the head unit's amplified output. Only downside is slightly high volume, but it's not too bad, it's mostly annoying when standing still. And you were right, the 2-amplifier buzz of old doesn't seem to be there anymore with the newer head unit, so that's no problem.
Thanks for the advice. I guess the lesson here is don't try to screw with a finely tuned system...
Dug into it again this weekend. Traced a bunch of wiring and found some issues (rear speakers not connected in adapter, amp in door corroded, bass speaker in LH door broken), but none of it solved the buzz.
Just powering the door amps without the rest of the wiring connected is enough to get the buzz - it seems like they need a strong enough signal to get over it.
I've now wired it in so the adapter does the steering wheel controls (works fine), and the speakers get driven by the head unit's amplified output. Only downside is slightly high volume, but it's not too bad, it's mostly annoying when standing still. And you were right, the 2-amplifier buzz of old doesn't seem to be there anymore with the newer head unit, so that's no problem.
Thanks for the advice. I guess the lesson here is don't try to screw with a finely tuned system...