[Jun Fan]

I replaced the head unit in my 2011 328i with a Pioneer AVH-2330NEX several years ago. The installation involved adding a RadioPRO unit for chimes and steering wheel controls and an AVIN MOST interface to go with the Logic7 factory amplifier.

Everything works sometimes. When I start the car, sometimes I have audio and other times there's nothing. Specifically, when I have no audio:
--The head unit works - all controls work and there is sound coming from the unit (tested by plugging in speakers to the RCA outs at the rear of the unit)
--The fiber optic cable to the amp is flashing (visually verified)
--The amp has power (amber LED is on at the opposite end)

At the time of installation, we replaced the head unit to see if that was the cause of the intermittent operation, and that didn't solve anything. I just lived with it until recently when I came across a used Logic7 amp to test, and that didn't solve the issue either.

I also put an optical bypass on the satellite unit to eliminate that possibility, and that didn't solve anything either.

I rechecked all the wiring and everything is secure. I don't think anything is shaking loose - this happens while I'm in park, and if I stop and restart it a few times, I might have audio again.

I'm almost to the point where I want to replace the Logic7 amp with an aftermarket amp in the hopes that it will be the end-all solution, but before I go that route, is there anything else I need to check or change or add to make this system work reliably?

[ctuna]

Are you sure your battery voltage is still good.
If to low the IBS could be cutting voltage to the amp.

[Canuck335]

By process of elimination it seems like it’s the Avin MOST interface.

[Jun Fan]

Originally Posted by ctuna

Are you sure your battery voltage is still good.
If to low the IBS could be cutting voltage to the amp.

The battery was recently replaced and is at around 14V (if I remember correctly) according to a scanner I was using to diagnose some other issues.

Is there another way that I can check to be sure? Maybe breaking out a multimeter and testing something somewhere?

[ctuna]

It's practically meaningless to do things based on what things where
what are they now yes go right to the multi meter.

[Jun Fan]

Originally Posted by Canuck335

By process of elimination it seems like it’s the Avin MOST interface.

I was thinking that too, and I was in a chat with the Avin folks who suggested going over my wiring to make sure everything was right. I did and all is right according to their instructions. My unit is out of warranty with them, so I'd either have to buy a new unit and hope that it fixes things (and if it doesn't, then I'm out $100 since they have a no refund policy for those units), or I go to plan B and get an aftermarket setup.

I suppose I could always try a different brand, but then I run the same gamble as I would by buying a second Avin unit.

If anyone has any experience with Avin or other MOST interfaces, I'd love to hear from you.

[Jun Fan]

Originally Posted by ctuna

It's practically meaningless to do things based on what things where
what are they now yes go right to the multi meter.

I probably should clarify that this intermittent condition was the same before and after the battery replacement about 6 months ago.

I'm not sure where I should be testing. I'm guessing the constant power and the switching wires?

[Canuck335]

Have you considered just bypassing Logic7 altogether and just running wires to the speakers?

You’d have to do some research on how to run wiring to the Logic7 amp area in the trunk, mess with crossovers and probably get a Technic harness.
But given that the Pioneer probably has excellent sound out of the box, I’m thinking you’d end up in a better place.

[ctuna]

Logic 7 amps only accept the Fiber Optic Input from the proprietary BMW
Most connection.

There are no analog Inputs on a Logic 7 Amp.

If you want to go analog you have to loose the Logic 7 amp
which means replacing a 9 channel amp.

[Canuck335]

Yeah but in his case the head unit contains its own amp.
I looked up the specs for his Pioneer - it puts out 4x50W.

[Jun Fan]

Originally Posted by Canuck335

Have you considered just bypassing Logic7 altogether and just running wires to the speakers?

You’d have to do some research on how to run wiring to the Logic7 amp area in the trunk, mess with crossovers and probably get a Technic harness.
But given that the Pioneer probably has excellent sound out of the box, I’m thinking you’d end up in a better place.

I actually hadn't considered that. I've been fixated on getting the amp to work or getting a new amp that I didn't think to see if I had a built-in amp already. That'll save a few bucks for sure.

Is this the harness you were talking about? https://technicpnp.com/product/logic...-applications/

I was looking at the manual and it looks like I can connect just about everything except for the center channel. I guess it's a small price to pay for a system that works reliably.

[Canuck335]

Actually this is the one.
https://technicpnp.com/product/logic...-applications/

I’m not familiar with doing this, so I’d recommend you contact Technic directly for advice and help.

[ctuna]

How is a 50watt per channel head unit that is more like 12 to 16 rms at level
that is not 10 percent distortion compare to a 9 channel amp if you have logic 7.
Have to read the spec's closely .
I have had Alpines Head Units with those amp an that 50w x 4 is not the same as
50 watt channel on a decent amp.

Technic does have a harness for those that want to totaly replace there Logic 7 amp.
It requires some expense on a significant aftermarket amp/dsp to get any quality out of it
though.

Logic 7 is a 9 channel amp
The technic harness for Logic 7 allows you to access the speakers and gives you
some RCA's to replace the fiber cable.
If you really want to replace it I would look at audiotec fisher DSP/Amps

Also that link only takes you to the front page of technic's website.

[simmonsshorovitz]

I wanted to replace my head units but after reading this post I understand that it is better to ask some professionals in this field to check the most reliable for my car and install it. I've thought it is not so hard to do, but the problems that may appear scary me.

[ctuna]

Do your homework first because a lot of pretty shoddy installers out there.
In London you should be able to find some good ones.
I would go to the UK technical sub forum here and try to find one.

[RocknRollOutlaw]

Hello, I have been having the exact same issue as you although I have an android head unit. Sometimes there's no sound on start up and I have to reset my head unit to get sound back. I also have logic 7 and am using a MOST converter box. I had come to the same conclusion as you that it had to be something to do with the MOST box. I am at a complete loss for ideas, I've scoured the internet and not found any solutions. If you find one please let me know.

[Jun Fan]

Originally Posted by RocknRollOutlaw

Hello, I have been having the exact same issue as you although I have an android head unit. Sometimes there's no sound on start up and I have to reset my head unit to get sound back. I also have logic 7 and am using a MOST converter box. I had come to the same conclusion as you that it had to be something to do with the MOST box. I am at a complete loss for ideas, I've scoured the internet and not found any solutions. If you find one please let me know.

I ended up replacing the Logic7 setup because I couldn't replicate the issue reliably enough to say that it was the MOST converter. I got a Technic harness (https://technicpnp.com/product/logic...-applications/) and bought extra RCA cables and an optical bypass. I replaced the amp with a JBL DSP4086 Everything sounds great now - I finally have sound that reliably fires up every time I start my car.