Re: Re: Re: Re: Re: Stereo
Aw, crap... Well that would be different info than my dealer told me, or what I've read here.
So... If the BOOST amp is internal, and inside the head-unit, does the radio provide seperate outputs as a balanced differential signal, or does the H/K and SoundModule systems get yet another single slot CD head unit, that looks the same as the 4x10, 4x20 units, but outputs just a signal level?
Balance differential signal And factory amps
Well a balance system uses two signal lines i.e. the + signal line and the – signal line. In an unbalanced system or in a single ended system you have only one signal line. The other half or reference is a ground point.
With balanced feed systems they have a far greater noise immunity that the unbalanced or single end systems. The reason for this is in the balance system any noise that is pick up on the feed lines is normally the same level in both wires. When the signal gets to the amp it is very easy to remove this noise, as it is the same on both signal wires.
In a balanced system the signal is normally the opposite on each wire. I.e. max positive on one wire and max negative on the other wire. So what the amp is doing is amplifying the difference between the two signals. Since the noise is the same on the two signal wires it in not amplified.
Most balanced systems use this difference theory, although they do not have to. But it is easier and cheaper to do so.
Now the boost Head unit has an upgraded amp module inside the head unit. The iceman has hinted on this before. To get these hight power levels from the head unit they would be using an audio amp family called BTL.
BTL is bridge tied load. This is when two amps are used in the final audio stage. One set of amps (i.e. the speaker + lead is the output of this set of amps) is driving its output up. The other set of amps (i.e. the speaker – lead is the output of the other set of amps) is driving its output down.
This means the load between speaker + and speaker – leads are see twice the voltage and 4 times the power compared to a single ended amp.
This is why you must never connect any of the speaker leads to ground or each other. As you might let out the magic smoke.
As you can now see that a BTL output provides the same signal to one output and an inverted signal to the other. This sounds like all we needed for a balanced feed, two signal wires and opposite signal on each.
So the input to the H/K amp and the Sound Modul amp is the speaker wires. On looking at the H/K system used in the E46 this is true. The H/K amp in the E46 just takes the 4 speaker outputs( 8 wires) and using them as the input to the amp.
I am guessing the wave head unit also use a BTL output, as it can be speced with the Sound Modul amp.
So the wrap up of this is the following guesses I have made about the system.
The H/K amp and sound Modul use the BTL output (speaker output) of the head unit as the input source.
The Boost head unit for the H/K option is the same unit used for normally Boost systems. Although the head unit must be told that is has a H/K amp so it can make some changes to its operation. Like not to use the speed related volume in the head unit as the H/K amp now does this, and to add the sound effects to the list of options on one of the buttons.
Remember these are guess about the H/K systems as no one has seen one. But they are educated guesses and if any one thinks one or all is wrong. Please correct me. As once we get to the bottom of it a FAQ can be done and everybody questions will be answered.