CitroenCrazy
- Sep 23, 2012
- 2
- Joined
- Sep 23, 2012
- Messages
- 2
For some while, I've been messing around with the Philips car radio / cassette player in my car.
The basic idea was to remove the entire cassette mechanism & use the audio input for an MP3 player. There are some pictures here:
http://www.flickr.com/photos/citroencrazy/sets/72157602218493745/
In brief, I traced the audio feed from the cassette to a Philips TEA 6320 chip.
This is described in the spec sheet as a sound fader control circuit, so it handles switching between inputs and volume / balance control.
Anyway, I lifted the pins associated with the cassette input and fed the audio output from an ipod into these pins.
In addition, there's a small circuit board that mimics the control signals associated with a cassette, but this has no effect on audio.
Getting to the question, I gave no thought whatsoever to impedance matching at the audio input. Although the quality of the sound is reasonable, there seems to be some background noise associated with the car, eg a faint whine that rises and falls with engine revs (it's a diesel car, so not ignition related). This seem to be more obvious when using the ipod input than using the FM radio, which is unmodified.
Anyone any suggestions as to how I could improve the audio input please ?
(For background, although I graduated in electronics, many years ago, I've never worked in the field, so I know what the words mean, but I'm short on practical experience)
Many thanks
The basic idea was to remove the entire cassette mechanism & use the audio input for an MP3 player. There are some pictures here:
http://www.flickr.com/photos/citroencrazy/sets/72157602218493745/
In brief, I traced the audio feed from the cassette to a Philips TEA 6320 chip.
This is described in the spec sheet as a sound fader control circuit, so it handles switching between inputs and volume / balance control.
Anyway, I lifted the pins associated with the cassette input and fed the audio output from an ipod into these pins.
In addition, there's a small circuit board that mimics the control signals associated with a cassette, but this has no effect on audio.
Getting to the question, I gave no thought whatsoever to impedance matching at the audio input. Although the quality of the sound is reasonable, there seems to be some background noise associated with the car, eg a faint whine that rises and falls with engine revs (it's a diesel car, so not ignition related). This seem to be more obvious when using the ipod input than using the FM radio, which is unmodified.
Anyone any suggestions as to how I could improve the audio input please ?
(For background, although I graduated in electronics, many years ago, I've never worked in the field, so I know what the words mean, but I'm short on practical experience)
Many thanks
