***Install aftermarket head unit in MOST car WITHOUT removing factory amp***
#32
05-02-2018, 10:13 AM
Registered User
Join Date: Apr 2018
Location: Athens GA Area
Age: 53
Posts: 212
Rep Power: 14 
The MOST conversion box could still be proving a constant digital audio signal even if you unplugged the analog pre-amp output from your HU or turned down the volume.
Have you tried disconnecting the power from the MOST conversion box and then turning off power to the HU? This would tell us if the pop is being caused by the AliExpress box.
How are you harnessing to the remaining factory radio cables?
Have you tried disconnecting the power from the MOST conversion box and then turning off power to the HU? This would tell us if the pop is being caused by the AliExpress box.
How are you harnessing to the remaining factory radio cables?
Last edited by ZuffenZeus; 05-02-2018 at 10:28 AM.
#33
05-06-2018, 09:18 AM
I disconnected power to the MOST conversion box leaving ground connected. No popping noise but no sound as well.
I had switched power from the Porsche harness connected to both the head unit and the MOST adapter. Constant power was connected from an unused factory cell phone harness to both the MOST and the Head unit. I tested these just to make sure they worked properly.
Perhaps if I install a timer to turn the amp off first before the head unit goes off the noise will go away. I found a couple of these inline timers on Amazon. I think when they are going off at the same time the noise is generated. Thanks for your advice by the way.
I had switched power from the Porsche harness connected to both the head unit and the MOST adapter. Constant power was connected from an unused factory cell phone harness to both the MOST and the Head unit. I tested these just to make sure they worked properly.
Perhaps if I install a timer to turn the amp off first before the head unit goes off the noise will go away. I found a couple of these inline timers on Amazon. I think when they are going off at the same time the noise is generated. Thanks for your advice by the way.
#34
05-06-2018, 10:08 AM
Registered User
Join Date: Apr 2018
Location: Athens GA Area
Age: 53
Posts: 212
Rep Power: 14 I disconnected power to the MOST conversion box leaving ground connected. No popping noise but no sound as well.
I had switched power from the Porsche harness connected to both the head unit and the MOST adapter. Constant power was connected from an unused factory cell phone harness to both the MOST and the Head unit. I tested these just to make sure they worked properly.
Perhaps if I install a timer to turn the amp off first before the head unit goes off the noise will go away. I found a couple of these inline timers on Amazon. I think when they are going off at the same time the noise is generated. Thanks for your advice by the way.
I had switched power from the Porsche harness connected to both the head unit and the MOST adapter. Constant power was connected from an unused factory cell phone harness to both the MOST and the Head unit. I tested these just to make sure they worked properly.
Perhaps if I install a timer to turn the amp off first before the head unit goes off the noise will go away. I found a couple of these inline timers on Amazon. I think when they are going off at the same time the noise is generated. Thanks for your advice by the way.
IMHO, you should use the constant and switched 12V power from the Porsche radio harness which feed the HU and frunk amp. Use the phone connector's switched 12V and ground to power and ground to the MOST conversion box. The amp could still pop when it's powered on, if there is a strong audio signal feeding regardless if it's an analog or digital type audio signal. It would be better if the MOST conversion box muted the digital audio signal, then turned off BEFORE the amp and HU when powering down the system.
My father was an military trained engineer and after his service, installed Becker radios in the Porsches back when we lived in Atlanta. As a kid, I enjoyed listening to his instructions and hearing all the in depth analysis of properly matching components on a audio system. Does that make me an expert? Absolutely not! hahaha But I learned a lot for him. He is still a very good bench technician that can get down to the component level on a circuit board. Why am I saying all of this? Because I've dealt with your problem many times over the years.
If I'm not mistaken, the proper start up and shut down procedure should go like this...
Power on > Head unit powers > 12V to amp turned on (internally or externally via pre-amp > audio signal sent to amp(s) > speakers receive signal
Power off > audio signal muted to amp(s) > Amp turned off > HU turns off
Because amp pops are common, some aftermarket units will allow you to delay the pre-amp audio signal output. This is a setting in the preferences menu. Unfortunately, we have NO way of knowing how the analog to MOST converter box is handling the optical signal output. It's probably keeping the digital audio signal active even if it sees an pre-amp analog signal or not. It probably comes on fully active when the switched 12V turns the unit on. That may mean that even if you can delay the audio signal from the HU, it will still cause a popping sound. If you could put a delay on the switched 12V feeding the conversion box, that would be a great test.
Hope you find a solution!
#35
05-27-2018, 03:48 PM
I have a different problem. I just installed my box and a Kenwood stereo. I had some wining noise when I started the car so I installed a noise isolator as well. I took it for a long drive and everything worked fine. On the way back the sound started to chip out - the sound comes and goes every couple of seconds. Turning off the HU I can hear a whining noise come and go. I stopped the car, turned off ignition and back on again. It is still there. Has anyone else experienced this? I suspect/hope there's some glitch (wiring). Will have to take out the HU to troubleshoot...
I was reading somewhere that someone else had a similar problem and the conclusion was that the box was bad. I sure hope that is not the case. It was working great for a while.
I was reading somewhere that someone else had a similar problem and the conclusion was that the box was bad. I sure hope that is not the case. It was working great for a while.
#36
05-27-2018, 07:19 PM
Problem solved.
I have a different problem. I just installed my box and a Kenwood stereo. I had some wining noise when I started the car so I installed a noise isolator as well. I took it for a long drive and everything worked fine. On the way back the sound started to chip out - the sound comes and goes every couple of seconds. Turning off the HU I can hear a whining noise come and go. I stopped the car, turned off ignition and back on again. It is still there. Has anyone else experienced this? I suspect/hope there's some glitch (wiring). Will have to take out the HU to troubleshoot...
I was reading somewhere that someone else had a similar problem and the conclusion was that the box was bad. I sure hope that is not the case. It was working great for a while.
I was reading somewhere that someone else had a similar problem and the conclusion was that the box was bad. I sure hope that is not the case. It was working great for a while.
#37
05-28-2018, 03:57 PM
Registered User
Join Date: Apr 2018
Location: Athens GA Area
Age: 53
Posts: 212
Rep Power: 14
#38
05-28-2018, 05:03 PM
I put in MPOW ground loop insulation that I had laying around instead of PAC-SN1. That fixed it.
The problem started when I turned on the vents above the HU. When I turned off the vents there was still some whining noise with the PAC loop isolation. The MPOW fixed it.
The problem started when I turned on the vents above the HU. When I turned off the vents there was still some whining noise with the PAC loop isolation. The MPOW fixed it.
#39
05-28-2018, 05:29 PM
Registered User
Join Date: Apr 2018
Location: Athens GA Area
Age: 53
Posts: 212
Rep Power: 14 Super! Ground loop problems are some of the most common issues with sound systems.
#40
07-19-2018, 12:13 PM
In case this might help someone else: someone mentioned that the alternator cable runs through the bottom of the center column next to the unused phone connector. Guess what - I moved the phone connector I use for 12v switch power to the MOST box as far away I as I could to the passenger side. The whining noise is gone and I no longer need the noise isolator.
#41
07-19-2018, 01:40 PM
Registered User
Join Date: Apr 2018
Location: Athens GA Area
Age: 53
Posts: 212
Rep Power: 14 In case this might help someone else: someone mentioned that the alternator cable runs through the bottom of the center column next to the unused phone connector. Guess what - I moved the phone connector I use for 12v switch power to the MOST box as far away I as I could to the passenger side. The whining noise is gone and I no longer need the noise isolator.
Moving the analog to MOST conversion box away from the high current power line is a smart decision. It's not uncommon that electronics lack the shielding necessary to prevent noise or interference from other devices.
#42
08-14-2018, 11:23 AM
In my case I get this anoying click or popping sound when the ignition is turned off even if the radio is off. Searching other car audio forums suggest that the problem is that when the amp goes off the noise is generated. Still looking into how to correct this but overall the stereo works well, a big improvement over the CDR-23 even with the same amp and speakers.
#44
08-12-2019, 02:06 PM
IMHO, you should use the constant and switched 12V power from the Porsche radio harness which feed the HU and frunk amp. Use the phone connector's switched 12V and ground to power and ground to the MOST conversion box. The amp could still pop when it's powered on, if there is a strong audio signal feeding regardless if it's an analog or digital type audio signal. It would be better if the MOST conversion box muted the digital audio signal, then turned off BEFORE the amp and HU when powering down the system.
My father was an military trained engineer and after his service, installed Becker radios in the Porsches back when we lived in Atlanta. As a kid, I enjoyed listening to his instructions and hearing all the in depth analysis of properly matching components on a audio system. Does that make me an expert? Absolutely not! hahaha But I learned a lot for him. He is still a very good bench technician that can get down to the component level on a circuit board. Why am I saying all of this? Because I've dealt with your problem many times over the years.
If I'm not mistaken, the proper start up and shut down procedure should go like this...
Power on > Head unit powers > 12V to amp turned on (internally or externally via pre-amp > audio signal sent to amp(s) > speakers receive signal
Power off > audio signal muted to amp(s) > Amp turned off > HU turns off
Because amp pops are common, some aftermarket units will allow you to delay the pre-amp audio signal output. This is a setting in the preferences menu. Unfortunately, we have NO way of knowing how the analog to MOST converter box is handling the optical signal output. It's probably keeping the digital audio signal active even if it sees an pre-amp analog signal or not. It probably comes on fully active when the switched 12V turns the unit on. That may mean that even if you can delay the audio signal from the HU, it will still cause a popping sound. If you could put a delay on the switched 12V feeding the conversion box, that would be a great test.
Hope you find a solution!
My father was an military trained engineer and after his service, installed Becker radios in the Porsches back when we lived in Atlanta. As a kid, I enjoyed listening to his instructions and hearing all the in depth analysis of properly matching components on a audio system. Does that make me an expert? Absolutely not! hahaha But I learned a lot for him. He is still a very good bench technician that can get down to the component level on a circuit board. Why am I saying all of this? Because I've dealt with your problem many times over the years.
If I'm not mistaken, the proper start up and shut down procedure should go like this...
Power on > Head unit powers > 12V to amp turned on (internally or externally via pre-amp > audio signal sent to amp(s) > speakers receive signal
Power off > audio signal muted to amp(s) > Amp turned off > HU turns off
Because amp pops are common, some aftermarket units will allow you to delay the pre-amp audio signal output. This is a setting in the preferences menu. Unfortunately, we have NO way of knowing how the analog to MOST converter box is handling the optical signal output. It's probably keeping the digital audio signal active even if it sees an pre-amp analog signal or not. It probably comes on fully active when the switched 12V turns the unit on. That may mean that even if you can delay the audio signal from the HU, it will still cause a popping sound. If you could put a delay on the switched 12V feeding the conversion box, that would be a great test.
Hope you find a solution!
Posting my solution which this thread helped me arrive at.
I have a 997 with bose. I replaced the HU for a Sony AX1005DB (great unit!) using the Connects2 MOST adapter cables. Everything worked great except for 2 things - no reception on FM and poping noise about 10 seconds after key was removed.
Solution for the FM reception was to connect a switched power source to the white wire that is in the Porsche harness connector (the connector also has the brown (ground) and red/green (12v) wires). This white wire is for the built in FM aerial amplifier which for some reason the Connects2 adapters do not cater for. I just tapped this white wire to one of the red switched wire in the Connects2 adapter harness.
For the audio pop I first tried a power delay module for the HU. The idea was to delay the power off of the HU to allow the Bose amp to power down before it. This didn’t work - all that this did was delay the whole problem! The HU stayed on for 15 seconds after the key was removed but so did the pesky amp! At least the pop noise would have now occurred when I’d left the vehicle!!
In the end the solution was simple. The Connects2 MOST adapter takes a switched 12v source (red wire) from the ‘powered amp control’ connection in the Sony harness (blue/white stripped wire). This was creating a non optimum power down sequence for my setup so I moved this from the blue/white wire to a normal ‘switched power’ red wire (in this instance I just used the one in the Sony harness that HU itself also used. I now have no pop noise as the MOST adapter (and amp?) power down at the same time with no ‘white noise’ being amplified.
Hope that makes sense - can post pics if needed.
Cheers
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