CTX-3305 | Optic Fiber decoder | BMW 1 series | BMW 3 series | BMW 5 series

The CTX-3305 Optical Fiber Decoder makes it possible to connect an aftermarket Android car radio to the in a neat and hassle-free manner original Top-HiFi sound system in your BMW. Thanks to this decoder, which uses the original fiber optic (optical) connection, you don't have to run cables through the car.

This way, you retain the original amplifier and speakers, while still being able to enjoy the latest infotainment features of an aftermarket car radio.

This optical fiber decoder is suitable for BMW models with:

BMW 1-series (E81/E82/E87/E88) – 2004 to 2010
BMW 3-series (E39/E46/E90/E91/E92/E93) – 2006 to 2011
BMW 5 Series (E53/E60/E61)
BMW X5 (E70) – 2007 to 2013

✅ Only suitable for vehicles with Top-quality Hi-Fi audio via fiber optics (MOST system)

How does the car radio fiber optic decoder work?

The CTX-3305 converts the digital audio signal running via fiber optics from the amplifier to the speakers into a usable signal for an aftermarket radio. This allows the original speakers and amplifier to remain fully active, while the audio source is replaced by your new car radio.

This way, you can seamlessly switch to Android, CarPlay, or other modern systems without any modifications to the original wiring.

When is the CTX-3305 required?

Two situations are shown in the images:

Situation 1: The green fiber optic cable is present and traditional speaker cables are missing. In this case is the CTX-3305 necessary.
Situation 2: Traditional speaker connections are present and no fiber optics. In this case the CTX-3305 is not needed.

Connect & Installation

The fiber optic connection is usually green in color and is located on the back of the original factory radio. The CTX-3305 It is placed behind the aftermarket radio and connected directly to the car radio and the fiber optic cable. No cables need to be run to the amplifier.

The installation is technically simple, but requires basic knowledge of car systems. The decoder comes with clear connection labels.

This product is only required for BMW models with Top-HiFi via fiber optic cable. Don't have an original premium audio system? Then the CTX-3305 is not necessary.

Frequently Asked Questions (FAQ)

Do all original speakers work with the CTX-3305?
Yes, all original speakers continue to function fully via the fiber optic (optical) channel.

Can I control each speaker individually?
No. Control is via a single shared fiber optic channel. Individual speaker control per channel is not possible.

Will the original amplifier be kept?
Yes, the original BMW amplifier (Harman Kardon/Logic 7/Individual/Enhanced Premium) remains fully active.

Do I need to reroute cables to an amplifier?
No, that is not necessary. The connection is made entirely behind the radio via the fiber optic connection.

Is the decoder suitable for every BMW?
No, exclusively for the mentioned models with Top HiFi and MOST fiber optic system.

Can I connect any aftermarket car radio with this?
Yes, the CTX-3305 is compatible with all common aftermarket Android car radios with an RCA audio output.

Important to know

This article is only necessary when your BMW is equipped with a Original Top-HiFi audio system with fiber optics (MOST). Without this system, the decoder is not needed, and a standard connection simply works via speaker cables.