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Wiring a bluetooth module into car radio, issue with switching between radio and blue

  • 08-02-2019 12:36PM
    #1
    davkav
    Registered Users, Registered Users 2 Posts: 512 ✭✭✭


    I have an old Blaupunkt Radio in my 91 VW golf. I have purchased a Bluetooth module from eBay and I have wired the line out from this into the Left and Right inputs to the amplifier that would normally be used for the outputs from the cassette player. The pre-amp for the cassette player is still wired in also, although the tape reader is disconnected.

    From the data sheet for the radio, I can see that when a tape is inserted, the audio source should switch from radio to tape. Here is a link to the data sheet. On page 5 of the linked PDF, on the top right of the sheet you can see the switching circuit for the audio inputs. I have wired my Bluetooth L and R inputs into R1304 and R1305. The input MS is set high when a tape is inserted into the radio.

    The problem that I am having is that the two audio sources are playing through the speakers at the same time.

    I have a few theories as to why and wanted to see what others thought:
    1. The pre-amp for the cassette player is still connected and is interfering with the switching circuit?
    2. The signal from the Bluetooth module isn't the same voltage as the pre-amp for the cassette so the switching circuit isn't functioning correctly?
    3. Maybe I need to wire the Bluetooth module line out into the cassette pre amp?

    I have some more testing to do this evening, it was getting late and I ran out of time, but if anyone has any thoughts on this I would greatly appreciate the help.

    Thanks, Dave


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