In todays newer vehicles we can no longer easily replace the factory radio. If we want to add aftermarket amplifiers we need to take the factory signal and convert it from speaker level to RCA low level for our new amplifier with a Line Output Converter or Digital Signal Processor.
What should you install for a basic setup? Line Output Converter OR Digital Signal Processor?
A line output converter is cheaper than a DSP and is easy to install as compared to a DSP where you will have to tune the DSP further. The factory speaker wires goes into the line output converter and then it converts it into low level signal which can be sent to the amplifier through a RCA wires. A premium line output converter will have some added functionality as well. The line output converter can be a 2 channel and 4 channel and even 6 channel as well depending upon the requirement. It will even have the level adjustments for the tuning purposes.
A premium line output converter or digital signal processor will be expensive but it will be worth for the install as they will have better filtering of the signals and they will have advanced features as well which will help to sound better than ordinary line output converter or digital signal processor.
There are basically two types of line output converters one is the active and second is the passive converter. The difference between the two is with the passive line output converter you not going to have any power connections and the active will have the power connections. Active line output converters are preferred as they gives us stronger output voltage which leads to a cleaner signal which gives better sound. The downfall part of line output converter is we cannot control the equalization on it. It will just convert the signal of the speaker level to low level only. If you have a decent audio setup with factory radio and you do not need very loud sound you can definitely go for line output converter only if you have a aftermarket amplifiers installed in the vehicle. You do not need any converter or DSP if you do not have any kind of aftermarket amplifiers installed.
NOTE: Do not buy any cheap or not branded converter to save money as they will sound crap and will destroy your sound output. The signal converters are the roots of the audio chain and if the roots are not good the sound cannot perform good. A good converter will send the signals as it is getting from the stock radio without changing the sine waves and the voltage as cheap and non branded converters result in changing the voltage artificially and will introduce distortion starting from the converter itself.
DSP (DIGITAL SIGNAL PROCESSOR) for high end setups!
A DSP is the best choice if you have a good budget for the install as it is expensive than line output converters but it is worth the price as it has proper tuning facilities and features like time alignment as well. A DSP give us the ability to control the crossovers to limit the bandwidth.
A DSP will gives us option to set the equalizer according to our taste which a line output converter cannot do. A DSP can be difficult to install as some DSP requires power connections within it to start and it will require extra wiring. With a DSP you can control the sensitivity of the input channel, phase settings for the subwoofer, crossovers and slopes, bass boost, time alignment which will align the sound of the speakers and subwoofers to the seats of the car. A DSP
A DSP is an improvement on line output converter. although you do not need to install both of them in a single install as it will cause less output voltage. A DSP can be 6 channel or even 8 channel as well. The advantage of having more channels is you can separately connect your mids and highs and subwoofers or even add extra speakers like midrange speakers if you want additional one. A DSP does not have manual adjustments like line output converter as a DSP is tuned through the computer via USB or even bluetooth also in premium DSP.
The advantage of choosing a DSP over a line output converter is that the factory radio manufacturers by default set the equalizer curve according to the speakers they designed for the vehicle to sound good. In this case you even if you set the equalizer to flat they will not sound flat, they will sound according to the curve the manufacturer applied to sound the stock speakers better. A DSP will fix that curve and make the sound much more better and according to your taste. If you have aftermarket speakers installed in your car and you have a stock factory radio installed, you should definitely go for a DSP if you have a budget for it as it will make the experience of the listening to the best. It will give a full control over the sound and the audio system of the car. In some cases while tuning the DSP you will need some additional gear like an RTA for fine tuning the DSP. A DSP will have a better output voltage than a line output converter which will make the sound distortion free even at high volume level. Nowadays the amplifiers comes with a built in DSP features and are compact in size and superior as well, Try to buy such amplifiers if you are planning a amplifier as it will be a future proof for your car for further install or upgrades.
If you are starting from scratching and planning to but car audio gears for your setup you can read this how to plan a car audio step by step! Which will help you how you can start with your audio in stages.