Hi all.
This is my first post (except for my intro) here so I hope I'm in the right place.
I guess mine is a common project, adding an auxiliary stereo input to a car radio / cassette player.
The stereo in question is a Blaupunkt ACR 3231 which has a very simple tape head reader. From reading up on-line I already knew that adding the line in RCA jacks to the tape head L&R channel wiring was not going to work but I tried it out anyway... and sure enough, the sound quality was very poor, and the volume of the auxiliary audio feed (in this case my smart-phone) needed to be very low for the sound from the stereo to be even intelligable.
Investigating more, I was able to identify the pre-amp chipset as a 6458DS, and I found the schematic on-line.
Having identified the output pins of the pre-amp, I thought that soldering the RCA positive channel wires to these pins would be the answer, so that my auxiliary audio was not passing through the pre-amp. Although the sound was better and the volume more reasonable, there were still problems however.
Firstly, the sound quality was OK with only the RCA positive wires connected, but too low to be useful, but as soon as the negative was connected to ground, the auxiliary line in audio became subject to a large amount of interference from the radio feed, which in theory was isolated by having operated the micro-switch which swapped the output audio from radio to cassette. When there is a quiet moment in the audio input through the RCA jacks, the radio can clearly be heard in the background the auxiliary input audio is simply being plaed over a reduced power radio feed.
The overall output volume is better though.
It seems then, that I need to move my RCA connections, from the output side of the 6458DS pre-amp and possibly directly to the input of the Multiplexor. which is an AN7465S. But this is where my capabilities have run out...
I cannot trace a direct circuit from the pre-amp to the AN7465S, and I do not understand the schematic of the IC well enough to know which pins may be the input from the tale head pre-amp.
Can anyone help?
This is my first post (except for my intro) here so I hope I'm in the right place.
I guess mine is a common project, adding an auxiliary stereo input to a car radio / cassette player.
The stereo in question is a Blaupunkt ACR 3231 which has a very simple tape head reader. From reading up on-line I already knew that adding the line in RCA jacks to the tape head L&R channel wiring was not going to work but I tried it out anyway... and sure enough, the sound quality was very poor, and the volume of the auxiliary audio feed (in this case my smart-phone) needed to be very low for the sound from the stereo to be even intelligable.
Investigating more, I was able to identify the pre-amp chipset as a 6458DS, and I found the schematic on-line.
Having identified the output pins of the pre-amp, I thought that soldering the RCA positive channel wires to these pins would be the answer, so that my auxiliary audio was not passing through the pre-amp. Although the sound was better and the volume more reasonable, there were still problems however.
Firstly, the sound quality was OK with only the RCA positive wires connected, but too low to be useful, but as soon as the negative was connected to ground, the auxiliary line in audio became subject to a large amount of interference from the radio feed, which in theory was isolated by having operated the micro-switch which swapped the output audio from radio to cassette. When there is a quiet moment in the audio input through the RCA jacks, the radio can clearly be heard in the background the auxiliary input audio is simply being plaed over a reduced power radio feed.
The overall output volume is better though.
It seems then, that I need to move my RCA connections, from the output side of the 6458DS pre-amp and possibly directly to the input of the Multiplexor. which is an AN7465S. But this is where my capabilities have run out...
I cannot trace a direct circuit from the pre-amp to the AN7465S, and I do not understand the schematic of the IC well enough to know which pins may be the input from the tale head pre-amp.
Can anyone help?