User 4221

Anybody connected an aftermarket amp to the CDR system?
I'd like to add a small amp and subwoofer to the car but, as far as I can tell, all signaling to the subwoofer is digital or PWM based.

Anybody find an analog attach point I can tap for amplifier input? Signal level is not important as the amp has a broad input range.

Tx,
Scott

ltc

Actually (and FWIW), the interface to the subwoofer IS analog.

The subwoofer is a slave to the MOST DSP amplifier in the rear cargo compartment; the MOST DSP amp is a node on the MOST ring, mastered of course by the CDR23 (or PCM).

Then again, what do I know about this stuff anyways........

User 4221

Thanks Lewis. I will pull out the O-scope today and dig a little further.

I got some weird readings last night but could have had my coupling settings wrong.

I plan to post a write-up so others can use this info so I may be bugging you for a little insight........ Which I've heard you may have

ltc

Me, insight? Into Porsche electronics?

Lies, all lies.

Budget M3

Is the analog feed to the subwoofer a filtered signal (i.e. only low frequencies), or is the filtering done at the subwoofer itself? Obviously there would be some degradation/attenuation of the signal due to all the extra equipment in the loop, but either way it would seem this is an easy way to hookup an aftermarket amplifier setup without losing the stock head unit (and steering wheel controls), right?

User 4221

Yep, it's analog. I just confirmed it is a low pass signal good for about 20- 150 Hz.
I used a CD with freq. sweep from 20Hz - 20Khz. The signal started outvery strong and rolled off nicely.

I'll post pics from my other PC shortly with the connector pinout, etc.
I also

Budget M3

Cool...I can see an amplified subwoofer in my future...

While you are in there, are the other speaker outputs also analog (and full range)?

User 4221

No full range inputs. That may be tricky as the head unit and DSP unit handle the crossover and audio functions. You would need to tie to the controller output to ensure you have proper DSP imaging.

Here's what I found........ Scope indicates analog output with 50 Hz signal. It was at moderate volume so I assume the signal would be a 5V drive. Thus, your amp would need to handle higher voltage inputs as most can today.

Next photo is the probe point where I captured the signal above.

Third is the connector pinout

Fourth is the factory sub...... Funny enough, I could not detect a difference in sound with it removed. I guess the door drivers handle a significant amount of sound....... The silver box is the 100 watt amp. I understand it's a PWM based ckt with efficiencies in the 90%, but the size is still striking.
Maybe Lewis can add his $0.02 here on why a wimpy 5-1/4 driver was chosen, too.

GM Austin

Amar was really big on 5 1/4 inch drivers. Bose has an abundance of them. In the Bose world, the 5 1/4 inch driver is a cost effective solution to many problems.

ltc

All EQ is done in the DSP.

Since you asked......
Yes, there is a very simple way to allow you to use the stock amp to drive secondary/aftermarket amplifiers, and thus maintain MOST ring integrity and steering wheel controls.

You simply run the MOST DSP amplifier with a flat equalization and then use the amplifier's (flat) outputs to drive whichever amplifier you chose to drive whichever speakers you prefer.

All that is required is a S/W update to orogram/load a flat EQ into the MOST DSP amplifier (update can be performed over the MOST ring via CDROM).

Then again, this is the internet, you can't believe everything you read.......

Budget M3

Well...I don't usually believe everything I read (Internet, NY Times, or otherwise), but you HAVE proven to be a trustworthy source of information up to this point...then again, this is the internet, you can't believe everything you read

Seriously, who/what/where/how can I get hold of that software update to flatten the EQ on the DSP amp? Sounds like something that will require much more than my laptop with a USB connection ...and if the amp is programmed for flat EQ to make this work, will I still be able to control EQ (bass and treble) through the MOST head unit?

ltc

The S/W (actually it's just a tuning file) can only be obtained from the designers of the MOST DSP amplifier.

No, it's rather simple. You simply insert the CDROM with the S/W update into the headunit's CDROM slot, wait a few minutes for the Flash memory to be updated and you're done. No tools required.

Yes.

Budget M3

Great!

Excellent!

Well...that sux...any idea where a poor "common man" can obtain such "exotic" s/w?

ltc

I'm afraid you're going to have to track down someone who designed the MOST DSP amplifier....and hope you're on his 'good' side

ltc

As a backup plan, you could always install a Clean Sweep, which will simply use another DSP to undo the EQ done by the amplifier's DSP:
http://mobile.jlaudio.com/products_c...php?page_id=94