2016 Porsche Macan main 9 channel amplifier

Hey all,

I don't care if you think Bose sucks. You need to take a peek at this mass manufactured multi-channel amp. In my 30 years in electronics development this one has captured my attention. They have optimized their design to the point where there they supply a decent amp with only a few manufacturing steps. This does not impact quality but significantly reduces manufacturing cost. If aftermarket brands could follow these design cues they could drastically reduce their cost to us. This is not a praise to Bose. It is just showing you what can be done with decent design practice.


Amp mounted in car
Attachment 10190


Extracted
Attachment 10191


To the left is a MOST25 optical communications buss connector from the head unit. To the right are the speakers out. The center connector is not connected. Maybe used for factory end of line test?
Attachment 10192


Variable speed intake fan to cool what's inside. I've never noticed fan noise from this amp even with the access cover taken off the vehicle. They must have a good strategy to only ramp up fan speed as the amp gets hotter.
Attachment 10193


Bottom plate. I can see stamping's to press against cooling points and holes to ventilate heat.
Attachment 10194


Back plate removed. Notice the rectangular contact patches on the PCB where the bottom plate touches to facilitate cooling. Notice the EMI shield over 1/2 the board. This is to minimize interference between high speed digital circuits and the sensitive analog circuitry.
Attachment 10195


Main board pulled out. Just like the sub-woofer amplifier this board uses Texas Instuments audio amplifier IC's. This is a 9 channel amplifier. The IC's have 2 channels each. The IC channels can be bridged for higher output. Heat sink contact points revealed. The 5 points with heat sink compound dissipate more power. This is most likely for mid-bass and maybe mid-range channels. There is one point with a thermal pad. Chances are this IC does not consume as much power and requires less cooling. Perhaps this supplies tweeters? Note, there is an even larger EMI shield on this side of the board.
Attachment 10196

I'm really digging these amp guts analysis posts, thanks for taking the time to do them. We rarely see OEM stuff and it's a great insight into how a company like Bose works to create decent performance at a minimal cost. Car manufacturing is so ruthlessly cost-driven, they must have to jump through a lot of difficult hoops with their OEM products.

That said, I gotta rant a bit. I generally hate how Bose stuff sounds and I get annoyed at how their successful marketing has conned so many people thinking into thinking Bose is a high quality brand. My old Mazdaspeed3 had a Bose system that was little more than Mazda paying Bose to put their name in the car. Friends would get in, see the Bose labels and act all impressed while the system sounded like garbage (the base non-branded stereo in my Golf sounded better). When I installed a new system I removed every Bose tag from the grills so that I wouldn't have to hear passengers mention it, also yeah, a bit out of spite:P

Day two of this write up.

Here is a zoom up of the heat sink. That little black patch in the center of the heat sink isn't from thermal damage. It appears to be ink. The sub amp also had one of these in side it. My best guess is that it is some mark put on inside the factory to signify the heat sink passed incoming inspection or had been through all the required machining processes?
Attachment 10330


Here is another shot of the boards top side. Notice the exposed copper (presumably ground plane) around the edges of the board that contact the heat sink for additional cooling. There is a torrid inductor on the power input and a large bank of capacitors. However, this does not appear to be a dual rail switching power supply like what you would find in typical high power amplifiers. There is only one winding on the torroid and no power FETs or rectifying diodes that would be required for the switcher. The audio amps run off the cars VBAT voltage and drive low impedance speaker loads to deliver more power. I believe the inductor and caps are just used for power supply filtering. The capacitors help hold the voltage up during start/stop engine cranking events.
Attachment 10331


Here is a shot with the EMI shield removed to reveal the high speed digital section.
Attachment 10332


Inside the EMI barrier is the SHARC DSP, a huge 16 bit micro, MOST transceiver, a set of Cirrus Logic multi-channel codecs, and switching power supply. This isn't the best by today's standards but was pretty damn powerful back in 2013 / 2014 when it was developed. There is an impressive amount of hardware packed into this small little chassis.
Attachment 10333


Here is the bottom side of the board with the EMI shield removed. Nothing spectacular here. You'll notice the beefy TVS diode off to the upper right hand side. That and additional exposed copper at the board edges that touches the bottom plate to facilitate cooling.
Attachment 10334


The 5 rectangular exposed pads on the bottom side of the board are positioned right underneath the amplifier IC's on the top side. The amplifier IC's have another heat slug underneath them that solders to exposed pads on the top side. The exposed pads on top and bottom side are connected together with through hole vias.
Attachment 10335


I'm a little concerned about the longevity of this amplifier. Exposed copper around the edges of the board should be tin plated. However, as you can see in the photo above much of the tin plating has worn off which exposes bare copper. Exposed bare copper will oxidize eventually. Maybe that makes a difference, maybe not. This amp has been through full automotive validation so I assume it will function as intended for at least 10 years. One thing is for sure, this amp has been through a few thermal cycles :). You can see the bluish discoloration of the exposed copper lands.

Let's talk a little bit about the amps cooling solution even though it does not require aggressive cooling.


As mentioned earlier here is a shot of the variable speed fan. It draws in cool air to blow over the heat sink fin stack. But what is the piece of black plastic over the top of the heat sink?
Attachment 10343


It's just a shroud to direct air flow. Here you can see an exhaust port on the other side.
Attachment 10344


Here is a shot with the shroud removed. The heat sink fins sit right on top of where the integrated audio amplifiers touch the heat sink on the other side. Some air is directed over the fins and exhausted out the other side. Some air is blown inside the amp to help cool parts inside.
Attachment 10345


Again, a shot of the bottom side of the heat sink. The fan vents to the inside of the heat sink are to the left and blow into the output stage cavity:
Attachment 10346


As mentioned earlier, the rectangular cut-outs and indents in the bottom plate touch the heat slugs on the bottom side of the board. The bottom plate then bolts to the heat sink to help transfer heat back into the heat sink.
Attachment 10347


Again, Bose is not my favorite audio supplier by a long shot. However, I need to hand it to them. This little amp is an impressive piece of hardware that has been optimized for high volume manufacturing. These things can be put together with minimal parts and process steps. I wish I had a way to connect to this thing with the engineering development software to see what it is fully capable of. But, that is proprietary BOSE stuff. I've never seen anyone hack into one of these amps using aftermarket tools.

Quote:

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Originally Posted by goatpanda

I'm really digging these amp guts analysis posts, thanks for taking the time to do them. We rarely see OEM stuff and it's a great insight into how a company like Bose works to create decent performance at a minimal cost. Car manufacturing is so ruthlessly cost-driven, they must have to jump through a lot of difficult hoops with their OEM products.

That said, I gotta rant a bit. I generally hate how Bose stuff sounds and I get annoyed at how their successful marketing has conned so many people thinking into thinking Bose is a high quality brand. My old Mazdaspeed3 had a Bose system that was little more than Mazda paying Bose to put their name in the car. Friends would get in, see the Bose labels and act all impressed while the system sounded like garbage (the base non-branded stereo in my Golf sounded better). When I installed a new system I removed every Bose tag from the grills so that I wouldn't have to hear passengers mention it, also yeah, a bit out of spite:P

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My entire point of making these posts was to show what high level of engineering went into making these amps. Suppliers like BOSE need to make the best product they can on a shoe string budget. By optimizing the design of these amps they have reduced manufacturing cost significantly. This helps lower the cost back to their customers who want to pay as little as possible. Bose still had budget left over to put an impressive grade of electronics on the board.

I know the rant about BOSE quality sucking. For as cool as these amps are they have still been know to produce a lot of crap. I've been in vehicles with Bose systems where i would rather turn the radio off vs. being subjected to listening to it. HOWEVER, the system in my Macan is surprisingly good considering what it is. If I had a way to put better quality loudspeakers in the car then re-tune the amps I may not rip the entire system out. However, the public does not have access to Bose engineering evaluation / calibration tools. So, I need to go aftermarket and put in amps that do give me full access.

Ge0