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New Radio Head Unit, High Pitch Hissing From Speakers
I just got a new head unit as the current one was buster, this was the cheapest plug and play I could find on Amazon. In the future I plan to get a better one with Carplay, but not today.
I plugged int he grey and brown plugs as well as the antenna directly, and it just worked. But whenever something is playing there is a bit of a high pitch hiss in the background. Is this from the 20+ year old speakers in my Disco 2, or the cheap head unit, or something else entirely.
Also, I know that there is an amplifier in this car, I'm trying to understand how that works. Is the amplifier in use with my current setup? Lastly, There is one cable not connected. This is the jack looking one next to the antenna, does anyone know what that is for? I assume the coloured blocks above the Grey and Brown plugs are for steering controls?
Speakers don't hiss on their own, no matter how old.
There's an entire subforum on here about audio, with several threads about the different plugs in the back of the unit. There are two antenna plugs on the stock unit, but only one will fit on an aftermarket box.
Depending on how things are connected, you may be bypassing the factory amp and your cheap unit is picking up interference, or you're using the amp and it's amplifying a not-great signal from your new cheap unit. You can usually add noise suppressors to reduce it, but a better unit is a better solution.
These are the outputs:
I'm using the ISO connector directly from the car
EDIT: I realised you probably mean is the output of the sound balanced left and right, in which case yes it is. I can also mess with the balance on the head unit from left to right and front to back without any issue
Last edited by Abandisco; Nov 5, 2024 at 06:56 PM.
Speakers don't hiss on their own, no matter how old.
Depending on how things are connected, you may be bypassing the factory amp
I was wondering if this was possibly happening, but I'm not sure how as I used the stock connectors, its wired the same way the stock head unit was with exception of the three coloured plugs and the second antenna. I'm assuming the three coloured connectors are for wheel controls, but maybe thats wrong?
Originally Posted by mollusc
You can usually add noise suppressors to reduce it, but a better unit is a better solution.
A new head unit is definitely the plan, but theres more important work to do before hand. This was just a cheap solution for the time being.
EDIT: I realised you probably mean is the output of the sound balanced left and right, in which case yes it is. I can also mess with the balance on the head unit from left to right and front to back without any issue
The factory head unit as well as the factory amp use balanced lines, so you need a unit with balanced outputs to properly drive the balanced inputs of the amp. If you have a mismatch, you will get noise issues definitely.
The BOSS unit has speaker outputs (8 pin ISO) and unbalanced outputs (RCA), but no balanced outputs. It looks like you connected the speaker outputs to the factory amp input, which creates a pool of problems (impedance & voltage mismatch as well as noise from the internal digital power amp) and then causes the noise. You need an adapter with integrated filters to correct this.
Last edited by Discorama; Nov 5, 2024 at 08:07 PM.
Still troubleshooting same issue with my D1. Suspect a signal isolator is needed between the radio and amplifier. There are at least two signal grounds for the radio, so an isolator can solve that. The ground loop (caused by multiple ground points) picks up high frequency interference (changes with engine speed) from things like the alternator, ignition, and injectors. First I will try to change the grounding so there is only one ground point (not a loop), when time allows.
The factory head unit as well as the factory amp use balanced lines, so you need a unit with balanced outputs to properly drive the balanced inputs of the amp. If you have a mismatch, you will get noise issues definitely.
Understood, thanks for the explanation and the link. I think I’ll leave it like this for now since it doesn’t seem to pose any danger of further issues and it’s a decent cheap fix. When I upgrade the head unit to one with CarPlay I’ll make sure it has balanced outputs.
I was wondering if this was possibly happening, but I'm not sure how as I used the stock connectors, its wired the same way the stock head unit was with exception of the three coloured plugs and the second antenna. I'm assuming the three coloured connectors are for wheel controls, but maybe thats wrong?
The top connector is for the speakers. The plug should be brown. The RCA connectors on your unit are amplified outputs for if you don't have a separate amp.
In the pictures you posted, the pins in the other connector (grey plug) don't include anything for steering wheel controls. That head unit only has permanent power, aux power, ground, and system enable pins.
New Radio Head Unit, High Pitch Hissing From Speakers
