996 MOST Bose PCCM+ quiet (sort of)

Car configuration first I guess: 2003 996 Turbo, originally fitted with PCM2 with Bose amplifier and speakers, over MOST optical. It's still a 2003 996 Turbo but has a PCCM+, still using Bose amp and speakers over MOST. On "full" volume on the PCCM+, on Android Auto (Tidal specifically), it's not even approaching loud, I can hear tire noise over it. MP3 and Radio are louder but still not by much. I'd expect "full" to be borderline on uncomfortable to listen to, like it is in most cars I've driven. Bass heavy stuff is fine but less bassy music I'd at least like the option of going a bit higher. I can't remember if the PCM2 was loud or not, I swapped it within a week of buying the car. Is there a secret gain control somewhere on the PCCM+ that isn't the screen where you set different input levels to match? The menu for balancing the different input levels doesn't affect the Android Auto (or Apple CarPlay) input and I can't find anything obvious in the Android interface (the actual head unit OS one, not Android Auto this time).

You have got the option to turn it on to loud. I thought exactly the same thing when I had mine fitted

When I installed my modern head unit onto my Bose + non-MOST car, I seem to remember reading that the Bose amp has a volume control all of its own which can only be changed by the original head unit. So to change it you’ll need to plug in the old head unit and turn the volume up high, and play some music to verify it’s loud. Then turn off the ignition, switch out the head unit for the new one, and hopefully it should be louder. Hope that works for you.

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I had forgotten about that! I'll dig the old one out if the loud switch doesnt fix my issues. Good call.

Loud switch sounds awful Cranking the volume right up with the old head unit didnt change anything, they're both MOST interface ones so I guess the new unit just set the amp to where it wanted to be. Thanks for your ideas anyway.

I guess you've done this already, but just in case... "Press the settings menu button and then touch and hold the volume section for 10 seconds. That will bring up another menu . Press the CAN switch button once to change from CAN to AMP and then restart the system" There's also a loudness option in there.

I found the line out voltage from the replacement head unit (not PCCM+ but a clone) was low, so I inserted a line driver like the one below between RCA out of the head unit and the RCA in for the BOSE MOST Fibre converter, this allowed me to wind up the input signal voltage and gave excellent results in terms of volume and 'punch'. The a decent graphic equaliser calibration on the new HU using an RTA app and mic on my iPhone made a world of difference to quality, the Bose system has lots of frequency gaps and peaks that I guess are normally tuned out by the PCM2 Audiopilot system, but reappear when signal is raw from a new source.

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I didnt realise the volume section had a hidden menu too, I'll try it in the morning. I had thought about a line booster type thing but it's all scuppered by needing to buy something to boost the analogue output, then something else to convert it to MOST for the amp - or replace the amp as well (...and speakers, sound deadening material in the doors, new sub box, feature in Max Power (RIP), etc).

Hopefully you found within the settings the option I mentioned to turn up the volume to loud. Not that it makes it ridiculously loud but it’s definitely an improvement on the base setting which you can hardly hear. When I get my car out today I’ll check mine to see if it gives any other options like the one Photek mentioned as that sounds different to what I did

Here's a link to the Porsche Technical Information Installation guide : link Pages 10 - 12 show the menu I mentioned earlier.

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I did a lot of research as I was trying to find out how the RCA-Fibre converter box actually worked, i.e. if fibre is an optical signal and not a 'voltage' then how could boosting the into voltage of an RCA into the fibre converter make the optical signal 'louder'... just did not make sense... so I bought one anyway and sure enough, even when converted to fibre for the BOSE amp, boosting the RCA voltage into the fibre converter actually worked, I got at least 40% more volume and punch than I had before, for the same volume on the head unit... still not quite sure how the fibre converter works, but it seems 'more power in = louder out'...

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Massive tangent, but: Analogue to digital converters work by recieving the audio signal, estimating where on a scale of 0-255 (or other arbitrary but not really number) how loud it is. Then transmitting that value as a piece of volume data. It gets converted back into analogue volume by the amplifiers digital to analogue converter circuitry by working out what proportion of, say, 88/255 loud is, expressed in a voltage* *With the massive caveat that it's far more complicated than that, for example, the frequency associated with that volume is another mathematical estimate. Here's the standards on MOST if you fancy being a Big Nerd™ https://www.mostcooperation.com/specifications/ The "book" at the bottom summarises a lot of it. There's far more than just audio being transmitted over MOST.

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I think that helped, it's increased the volume of the Android/CarPlay mode enough that when I turn the other modes back down, they're all loud enough over the engine noise. Analogue to digital converters interpret the range of 0v to 1v into 1-256 levels of "loud" then transmit this volume data along with the frequency data to the amp, which coverts it back. 0.5v analogue volume would be converted to 128, then converted back to 0.5v at the digital to analogue converter in the amp. If you get 0.5v out of your source, boost it to 0.6v, then run it into the fiber converter, it translates to 154, then back to analogue at 0.6v. Only caveat is that I have no idea what voltages in car analogue audio is and assumes 8-bit digital volume, might be incorrect. Principally that's how it works though.

Could have sworn that first one didnt post

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So can this be used with factory amp/fibre optic? And possibly used to provide front/rear adjustment in the event that fader is lost? I have the BOSE system with fibre and factory amp. I have upgraded the speakers but the head unit appears to be an Ali Express special and needs swapping too. I'm trying to decide whether the factory amp is worth keeping, and find a HU that is a good match. Or whether its better value for money swapping the OE amp too. I want wireless CarPlay and a decent screen (my 996 is convertible) and have been looking at the Kenwood DMX8021DABS or Alpine iLX705D. Although I have read that the screen on the Kenwood is not great. I have discounted PCCM+. Any thoughts appreciated.