CTX-3305 | Fiber optic decoder | BMW 1 Series | BMW 3 Series | BMW 5 Series

The CTX-3305 Optical Fiber Decoder allows you to connect an aftermarket Android car radio to the original Top-HiFi sound system in your BMW in a neat and hassle-free way. Thanks to this decoder, which utilizes the original fiber optic connection, you do not need to route any cables through the car.

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

This fiber optic 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-HiFi audio via fiber optic (MOST system)

How does the car radio Fiber Optic Decoder work?

The CTX-3305 converts the digital audio signal that travels via the fiber optic cable from the amplifier to the speakers into a signal usable by an aftermarket radio. This keeps the original speakers and amplifier fully active, while the audio source is replaced by your new car radio.

This allows you to switch to Android, CarPlay, or other modern systems without making any modifications to the original wiring.

When is the CTX-3305 required?

The images show two situations:

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

Connection & Installation

The fiber optic connection is usually green in color and is located at the rear of the original factory radio. The CTX-3305 is installed behind the aftermarket radio and connected directly to both 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 labels for connection.

This product is only required for BMW models with Top-HiFi via fiber optic. If you do not have an original premium audio system, the CTX-3305 is not necessary.

Frequently Asked Questions (FAQ)

Do all original speakers work with the CTX-3305?
Yes, all original speakers remain fully functional via the fiber optic channel.

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

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

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

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

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

Important to know

This item is only necessary if your BMW is equipped with an original Top-HiFi audio system with fiber optic (MOST). Without this system, the decoder is not needed and a standard connection will work simply via speaker wires.