Octavia II Scout DPS Amp bypass or replacement.

[Kiwibacon]

I've fitted an android head-unit in place of the Audience MP3 in my Octavia 2 Scout.  This car has the 12 speaker system with a DPS amplifier under the passenger seat.

 

The amp is allegedly activated by Canbus and I cannot get it to respond.  So no sound out the speakers.  Everything else on canbus works fine.  I have tried the battery disconnect trick with no success.  Plugging the old head-unit back in works fine.

 

So what options exist for plug-ins to bypass or replace the existing amplifier?  Are there any?  I presume this setup is common to many VAG group cars but I don't have the right search terms to find them.
Manually splicing two dozen wires is a last resort at this stage.  I'd far rather order something from the other side of the world and wait for it.

[Kiwibacon]

So interesting development.

Today after an oil change and service reset I used VCDS to check block 47 - Sound System.

 

The amp turned on for about 3 seconds and the speakers played.  Then it stopped.

Repeat the test and same every time.

 

So it appears VCDS has some ability to turn this amp on.  But how do I do it longer term?  Does anyone know how the VCDS coding works for this block?

[Kiwibacon]

Today I pulled out the passengers seat, pulled the factory amp and set to identifying wires.

 

There are two connectors.  I'm calling them A and B.

B is the input.  Looks like a pair of power wires and 8 inputs.  These inputs are speaker pairs and direct connection to the block connector behind the head-unit.

A looks like output.  It's got a couple of bigger likely power wires and then 20 others.

 

I'm out of time for today but I've identified one pair of pins in the connector A that powers up the mid and tweeter speakers on the LHR door.  Jumping those across to inputs on B gives me sound.

 

So far soo good.  I purchased 4 three-way filtering cross-overs from Aliexpress and planned to wire those in place of the factory amp.  But I should have counted wires first.  It appears I may only need 2 way crossovers.  We shall see.

Edited 26 February, 2023 by Kiwibacon

[Kiwibacon]

Fixed and it sounds great.  I spliced four cross-over filters in place of the main amp.

 

The car has two feeds to each door.  Main and tweeter are on the same feed and will have some filtering somewhere.  Woofer has it's own feed.  Head-unit has only one feed for each door.

 

Wire colours:
From Head-Unit on plug A.

Pins 20/21 White and Brown feed for Right Rear speakers.

Pins 17/18 Black and Brown feed for Left Rear speakers.

Pins 14/15 Green and Brown feed for Right Front speakers.

Pins 11/12 Blue and Brown feed for Left Front speakers.

 

To Speakers on plug B.  These are all twisted pairs.

Pins 1/2 White and White/Brown to Left Rear Mid and Tweeter

Pins 4/5 Blue and Brown/Blue to Right Rear Woofer

Pins 3/6 Red/Green and Brown/Green to Left Rear Woofer

Pins 7/8 Yellow and Brown/Yellow to Right Rear Mid and Tweeter

Pins 10/11 Red/Yellow and Brown/Yellow to Left Front Mid and Tweeter

Pins 12/15 Blue/White and Brown/White to Left Front Woofer

Pins 13/14 Red and Brown/Red to Right Front Woofer

Pins 16/17 Blue/Black and Brown/Black to Right Front Mid & Tweeter

 

This leaves 2 wires on plug A and 6 wires on plug B unused.  A look like Canbus and B look like power wires for the original amplifier.  I plan to bundle them safely and leave them in the connector.

 

Filters/Cross-overs:
I purchased 3 way cross-overs (from aliexpress) with woofer, mid and tweeter outputs because I thought they were needed.  They're not. 

I found the mid-tweeter setup sounds best when driven straight from the head-unit feed, I was losing top-end clarity when it was connected to the "mid" and sounding scratchy when connected to "tweeter".  Connected directly to the feeds they mid and tweeters sound great.
So I'm only using the cross-overs to filter the woofer inputs.  Which I could have acheived a whole lot quicker and cheaper with smaller units that have fewer connections.

 

Wiring:
I just had to identify and label the wire pairs, extend them and wire them in.  It's not difficult work but takes a methodical approach.

 

Other than that I've lost the button functions on my chinese android head-unit and the slot in the face that looks just like a micro-SD card slot isn't.  Feed a card into that and it's not coming back!

 

Hopefully this can help someone else.