Experiments with cheap MOST optical interface
04-06-2018, 02:23 PM
#1
Racer
Thread Starter
Experiments with cheap MOST optical interface
A few weeks ago I ordered a MOST optical audio interface sold by Seicane. These are the made-in-china boxes with 2 RCA audio inputs, ground, power, switched 12v and the optical block connector on them. I also got a fiber optic cable from a Chinese vendor on ebay, this just made it easer to experiment without taking anything apart in the car.
It's easy to unplug the optical cable from the Bose amp. Just push the seat all the way forward to reach it. There's a latch and it comes right out. Then I just plugged the optical cable I got right into the amp. Easy peasy.
The other was plugged into the MOST adaptor and I powered it up with my iPhone on the audio inputs.
Once the MOST interface is powered, it begins flashing the red LED on the optical interface. This signals the Bose amp to turn on. No need for any other signal from the car or even to put in the key. The amp just turns on as soon as there's a data link turned on at the optical input.
All in all, it worked as expected. I could play music on the phone, control volume and EQ. The Bose amp simply runs in whatever state it was in - fader settings, effects, linear or optimized. The MOST box only puts stereo audio on the optical bus, the Bose amp does the rest of the processing. With surround mode on, all speakers including center were active. Subwoofer was active too.
The downside: Unfortunately, this box has an internal engineering issue on the input side. With the volume turned down or muted from the input, there's a steady hiss, which is normal, but there's also a series of undertones that are audible going on. These audible defects were present at low volume and were still present with no input connected, and even with the RCA inputs shorted to their own grounds. This means the noise originates inside the interface box itself. I've run into similar problems with A/D designs that didn't have well thought out analog sections and grounding in their board designs.
So bottom line, this particular cheapo made-in-china box is a bust.
The Nav-TV MOST HUR product is not the same box. I haven't tried the MOST-HUR, but if they did a good job with their design and board layout work, it should be fine. On the other hand, one could buy some nice compact amps that will fit in the same spot as the Bose amp for the same or less money, and retain fading control.
It's easy to unplug the optical cable from the Bose amp. Just push the seat all the way forward to reach it. There's a latch and it comes right out. Then I just plugged the optical cable I got right into the amp. Easy peasy.
The other was plugged into the MOST adaptor and I powered it up with my iPhone on the audio inputs.
Once the MOST interface is powered, it begins flashing the red LED on the optical interface. This signals the Bose amp to turn on. No need for any other signal from the car or even to put in the key. The amp just turns on as soon as there's a data link turned on at the optical input.
All in all, it worked as expected. I could play music on the phone, control volume and EQ. The Bose amp simply runs in whatever state it was in - fader settings, effects, linear or optimized. The MOST box only puts stereo audio on the optical bus, the Bose amp does the rest of the processing. With surround mode on, all speakers including center were active. Subwoofer was active too.
The downside: Unfortunately, this box has an internal engineering issue on the input side. With the volume turned down or muted from the input, there's a steady hiss, which is normal, but there's also a series of undertones that are audible going on. These audible defects were present at low volume and were still present with no input connected, and even with the RCA inputs shorted to their own grounds. This means the noise originates inside the interface box itself. I've run into similar problems with A/D designs that didn't have well thought out analog sections and grounding in their board designs.
So bottom line, this particular cheapo made-in-china box is a bust.
The Nav-TV MOST HUR product is not the same box. I haven't tried the MOST-HUR, but if they did a good job with their design and board layout work, it should be fine. On the other hand, one could buy some nice compact amps that will fit in the same spot as the Bose amp for the same or less money, and retain fading control.
04-06-2018, 04:05 PM
#3
Rennlist Member
Thanks for the review Larry. Too bad the cheap MOST doesn't work well. With the cost of the Nav-TV MOST HUR, I think the best option is to replace the Bose amp when replacing the head unit.
04-06-2018, 04:14 PM
#4
Several reviews around. Mine and other peoples had no noticeable hiss and I get zero "undertones." It would be interesting to buy the NAVTV one and open them both up to see the differences 
https://rennlist.com/forums/997-foru...s-or-less.html
It would be interesting to find out what was causing your noise issues since they are not present in all the boxes. Any ideas? If its a quality control issue with some folks getting it and some not maybe there is something that can be done to keep it from happening?
Mike
https://rennlist.com/forums/997-foru...s-or-less.html
It would be interesting to find out what was causing your noise issues since they are not present in all the boxes. Any ideas? If its a quality control issue with some folks getting it and some not maybe there is something that can be done to keep it from happening?
Mike
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