The Bose amplifier is triggered ON/OFF via the single wire in the YELLOW mini-ISO plug (wire C6). This wire must subsequently be connected to the REM OUTPUT wire from your new headunit (usually BLUE/WHITE), which supplies the +12V signal.
There are options to make this connection:
1. fit matching mini-ISO terminal/plug onto end of REM OUTPUT wire and connect to mini-ISO plug
2. cut off YELLOW mini-ISO plug and attach matching (bullet) terminal onto wire and connect to REM OUTPUT wire
The audio signal from the factory headunit comes via the speakerwires. In 'Bose mode', the headunit provides a 'low level' (low voltage) signal. When no Bose amplifier is fitted, the speakerwires provide a 'high level' (amplified) signal to drive your speakers directly.
To connect audio to the Bose amplifier from your new headunit, it is preferable to use the RCA preouts. This is because the signal bypasses any internal amplifier ICs, so remains of optimal quality (low distortion, higher clarity/bandwidth/signal-noise-ratio). Because the preouts use 'phono' style terminals, and because the Alfa plug is ISO style, it is recommended to use an RCA-ISO adaptor harness. You can either construct your own, or buy one like the nexxia PC2-36-AMPR.
The PC2-36-AMPR includes a mini-ISO connection for the REM OUTPUT wire. You can purchase the PC2-36-AMP alone, which does not include the remote connection.
NOTE: when utilising RCA preouts, two important conditions should apply:
1. buy a headunit with at least 2 sets of RCA preouts (4 channels); the Bose amplifier relies on 4 channels of audio input; utilise the 'front' and 'rear' preouts (not 'sub' preout)
2. buy a headunit with at least '4V preouts'; this strength of output is required to drive the Bose amplifier to high volume; if the signal is lower voltage (eg: 2V or less), full volume on the headunit may not offer a signal powerful enough to drive the amplifier to high volume
NOTE: when using the RCA preouts, your new headunit's speakerwire ISO plug remains disconnected
NOTE: if you do not have a headunit meeting the above conditions, it is recommended you utilise the 'speakerwire' outputs, which are higher voltage; this usually means simply plugging the supplied headunit's speakerwire ISO plug into the corresponding Alfa ISO plug; because the signal may be higher than the factory headunit, the volume may be very loud with only a low setting on the volume control, and each increment of change causes a relatively large change in volume; unfortunately, there is no 'happy medium' between using the low level preouts and high level speakerwire outputs in this situation; the Bose amplifier sensitivity cannot be adjusted
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