New amplifier & microphone?

Not knowing what the symptoms are, it is difficult to figure out which parts would have to be replaced. Here is a rough idea of how the system works.

The navigation, radio, DVD, and CD changer are all housed in one unit. It sits behind the brushed aluminum plate in the front and is held on by four bolts. There are a number of connectors (around 19) that go into the back of the unit.

I believe there are three microphones in the XLR. One is for measuring the ambient sound (the "noise compensation microphone") and is used by the DSP. The other two are noise cancelling microphones and are used by the Onstar and voice recognition systems (both mics are used by both systems, if that makes sense). Those microphones are made by Andrea electronics.

The speakers are, of course, separate. The signals for the speakers come from the back of the main nav/radio unit.

So, unless one of the microphones is malfunctioning, the nav/radio unit would be the likely source of any problem. There is nothing really difficult about replacing that unit if you have the service manual and the parts.

If you can provide more details, I *might* be able to be more specific.

ctsvman said:

I believe my vette has 350 but not sure.
Note that I use the XLR's DSP with it set to spacious on CD's & XM radio.

Click to expand...

The XLR is a 250 Watt system. Since Wattage is logarithmic, the difference between a 250 Watt system and 350 Watt system is barely noticible, if at all. To get twice the power of a 350 Watt system you would need a 3500 Watt system. Half the power is a 35 Watt system.

So, what is going on with the XLR? It isn't the power amps, but the inputs to the amps (IMHO). Try a simple test - without changing the volume level, play an XM source and then play an AM source (if someone else is trying this who doesn't have XM, try a low level CD). You'll hear quite a bit of difference in level. I've found that the XM input level is significantly lower than what is used for CD or the other radios. I'm not sure why GM did this, but I don't know of a thing that can be done to change it.

On the noise compensation microphone, I notice too much of a change when I stop at a light, so I've disabled the function (using the button with the musical note to the left of the LCD). If you aren't noticing any difference, you might have your dealer check the microphone next time the XLR is in for service. I assume you've tried disabling the noise compensation to see if that improves your audio output levels??

You may find you are pretty much stuck. I haven't seen a way to change the input level and the amplifiers are actually more than powerful enough (if the input level was high enough). I'm hopeful that something is wrong with the noise compensation system and it that is what is causing your loss of level (not having heard the problem, it is difficult to say for sure). With the roof closed, it should be impossible to have a conversation with the XM all the way up, but not ear-bleeding volume.

The problem with any upgrade is that almost everything is integrated into the Nav/DVD/Radio/CD Changer unit. There are outputs to the various speakers, but I'm not sure if those are line level (going to a speaker amp like on some of the earlier Bose systems) or if they are speaker level.

If they are line level, then you could boost those but then you might overdrive the speaker amp. If they are speaker level, you would have to drop back down to line level and then amplify the signal. That is off the top of my head, so I would definately get a "pro" to look at the output before trying any modifications.