nicholsvt

Hello,

I have a 2006 C4 with limited options, in particular just the stock speakers and ASK amp and without any modifications. I installed the PCCM+ along with new OEM door and rear speakers. While the sound quality is significantly better than before, especially considering I had several blown speakers, it seems too loud (at 7) and there is a persistent white noise even when the volume is at 0. After reading through other threads, I tried isolating the issue by unplugging the AMP, but the noise persists. I also tired the original head unit and don't hear the white noise although the overall volume is lower. It just feels like the gain is too high on the PCCM+ which I was hoping would have been isolated to the amp. Probably unrelated, I noticed that the Configure PCCM+ menu shows that the MOST BUS is NOK, although I haven't noticed any other issues in the dash, etc. While the stereo is admittedly the least important part of this car, I would greatly appreciate any insight in resolving this issue. It would be nice to have an updated head unit especially considering the cost.

Thanks in advance.

Regards,
Jason

Luban

Hi Jason,
I don’t have a solution, but have the same issue with white noise.
My 997.1 C2S cabrio 2008 EU-version had the sound package plus (ASK AMP; no Bose), no Nav, no CD-Changer, no phone. No modifications, totally original condition.
I installed the PCCM+, done the auto configuration and all the settings, everything is working perfectly, having great and much better sound, great volume range, but at Mute and volume 1 I hear white noise, even at vol.2 I can identify it in the background.
It’s independent from the source (radio FM or DAB+, bluetooth, carplay), everytime there.
I have aswell MOST BUS NOK in the self diagnosis.


I tried 2 pieces of ASK AMP, I tried to disconnect the ASK AMP, white noise still there.
When I reinstall the PCM2.1 noise is gone, absolutely clear and silence.
It seems not all units are affected, so here is my firmware:

PCCM+ Firmware

I don’t have any other idea what else to try out 🤷‍♂️

Regards
Luban

nicholsvt

Hi @Luban ,

Thank you for the quick and thorough response. I should have been as detailed, but I've performed everything exactly as you've outlined with the same results. Here are pictures from the version info menu:





I'm out of ideas as well. It just seems like the gain setting on the PCCM+ is too high. Some people have mentioned using one of these adapters (https://connects2.com/Product/Produc...AMPPASSTHROUGH or https://www.porschemarinparts.com/oe...er-99664234100), but I'm not certain if they apply to our setup. If it is a known firmware issue, is there any process to update the firmware or have the dealer replace the unit? If anyone reading this has any insight on how to address the white noise / gain issues, please share!

Regards,
Jason

nicholsvt

@Luban I went ahead and ordered the following parts:

• Connects2 CTAMPPASSTHROUGH: https://www.ebay.com/itm/265485718771
• Wiring Harness Adapter For Loudspeaker - Porsche (996-642-341-00): https://www.porschemarinparts.com/oe...er-99664234100

I'm not sure that either will work, but I'll let you know. I should get the second one next week. I might be delayed installing the first one due to travel obligations.

Luban

ok, thanks, keep us updated please, when there are some results 👍

Luban

I sparked the discussion to white noise in the german pff-forum again.

There are some people with exactly the same white noise behaviour like us:
- gain of the PCCM+ amplifier is generally very high (vol. 5 is quite loud, vol.10 is super loud; of course subjectively assessed)
- white noise is noticeably hearable at mute or vol.1, but somewhere at vol.2 and more you cannot hear it anymore
- the only occasion without white noise is in development mode - mute the pccm+ internal amplifier. Then there is no sound at all of course.


And I’ve found at least one guy with 997.1 w/o Bose having no troubles with white noise. His PCCM+ has been delivered in October 2023 to his dealer and installed by the end of the month. I hope he reads the post and replies with his firmware version. I’ll keep you informed.

moe01325

I ordered and installed a CTAMPPASSTHROUGH for my 997 with the ask amplifier. initial problem was white noise at volume 0-2. already too loud at 10.

now with the CTAMPPASSTHROUGH installed, no white noise. sound starts to be hearable at 5. 30 is just OK sitting in the car without engine noise. so the volume level was reduced, but reduce too much...

conclusion for me: better without the CTAMPPASSTHROUGH.

Luban

bad news, but thank you very much for sharing the info!

moe01325

as somehow expected, the CTAMPPASSTHROUGH is a quite basic setup of capacitors and resistors. unfortunately i am not very proficient in electronics...
so i would need quite some time to figure out which parts/layout would work...

AndreSilva

Hey OP.

Just curious if you managed to fix the issue. Got a brand new PCCM+ and have the exact same hissing sound, not sure what the problem can be, I checked all the connections and everything looks good.
It's not antenna-related because it also happens with Bluetooth and when the sound is at 0

PorscheCambs

Hi,
RE. White noise fix for PCCM+ audio when interfaced to the ASK amplifier.
I managed to fix the issue with white noise on my 2005 Porsche Boxster with ASK amplifier. But it involved making a custom cable using an 8 way in-line ISO car audio extension cable with 4 in-line 12ohm 25W wire wound resistors (available on either Amazon or EBay). The resistors soldered in on each half way (either + or -), to increase the load to 16ohms per channel. White noise is completely removed and volume sensitivity as expected in the 0 to 30 range. Suddenly the PCCM+ sounds fantastic.
Hopefully other Porsche owners with the issue can benefit from this post. Message if you need more detail.
Regards, PorscheCambs.

Loko

This is great news. I’ve been trying to attenuate the units output but not managed to fix it. The PCCM plus unit is 4x45W amp, do your resistors get hot? The power of each channel will now be shared between resistor and the speaker.
I’ve tried a coupe of adjustable amp integration cables on the brown iso cable but they lower too much the volume.
Just adding a resistor alone will cause a problem with the impedance varying with frequency such that it can change the behaviour of the speaker. It depends on the speaker itself as to how different it may sound. Did you try 4 ohm resistors to achieve 8 overall? I would have thought going from 4 ohms to 16 per channel would have quietened it too much.

PorscheCambs

I tried 4ohm, 8 ohm and 12ohm. It needs 12ohm to work well with the 0-30 volume range.
Sound quality is excellent, using USB with mp3 at 256-bit.

No problems with heat, I did trial 8 resistors at 6ohm, as I too was worried about heat. But 8 resistors is quite bulky.

PorscheCambs

I mounted the resistors on two copper plates in an aluminium housing. Soak tested for 30 minutes with very little heat generated at a volume of 10, which is reasonably loud, but comfortable. On mute, no white noise whatsoever. In terms of audio quality, better than the Bose in my 2024 Audi.
I previously tried one of those CTAMPPASSTHROUGH, designed to drive a pre-amp, and it was dreadful. Way too much attenuation (designed to drive 20k ohm or more) and extremely distorted. ASK amplifier is designed to take Speaker load at input.

PorscheCambs

I have also tried many different options to try and solve the white noise, it seems you have been down a similar path.

I tried one of the these variable attenuation step downs, but they are designed to output at phono level, and the ASK amplifier is unusual in that it takes speaker level input: “Connects LP3-4 LocPRO Series 4-Channel Line Output Converter for OEM or Aftermarket amplifiers”

Both the Connects2 LP3-4 LocPRO and the CTAMPASSTHROUGH are a complete impedance mismatch with way too much attuation and the audio quality is dreadful.

Regarding the in-line resistors:
I tried 4ohm, 8 ohm and 12ohm. It needs 12ohm to work well with the 0-30 volume range.
Sound quality is excellent, using USB with mp3 at 256-bit.

No problems with heat, I did trial 8 resistors at 6ohm, as I too was worried about heat. But 8 resistors is quite bulky.

The quoted unit 45W x4 will be peak, converting to RMS, it is more like ~30 watts per channel.

You can get higher wattage resistors, 50 watt, but they are bulky.