Hello experts!
I'm an electronics engineer student trying to hack a HiFi and I have a simple problem but I'm not sure which is the (best) solution.
The thing is that I found a Sharp Micro HiFi (similar to this one) having a decent loudspeakers. The CD is broken but both the radio and cassette work perfectly, and I thought I could use the whole HiFi as an external amplifier+speakers for my laptop/mp3/etc and so my idea was to find a way to add a stereo audio input to the amplifier board so that I only had to plug a regular headphone output to it.
The HiFi has a dedicated board for amplifying the audio signals, drive the speakers and handle the radio system. I found the two traces in the PCB which carry the radio audio signals prior to be amplified and I disconnected them and made a simple board with a DPDT relay to switch between the existing radio signal or my external headphone signal. The problem is that when I switch to the external signal (coming directly from an MP3 stereo jack) the volume is really low and barely audible.
The PCB trace comes from a DC-blocking capacitor which is connected to the radio IC. I have no clue of its output impedance or the input impedance of the adjacent amplifier...
At first I thought the problem was the voltage level, but it's not. If I plug in my Android mobile, which happens to have a higher level, I can certainly hear distortion at higher volumes. Besides, the voltage levels when the radio is connected are pretty much the same. So I guess the issue must be related to unmatched impedances then? What do you think?
Thanks in advance!!
I'm an electronics engineer student trying to hack a HiFi and I have a simple problem but I'm not sure which is the (best) solution.
The thing is that I found a Sharp Micro HiFi (similar to this one) having a decent loudspeakers. The CD is broken but both the radio and cassette work perfectly, and I thought I could use the whole HiFi as an external amplifier+speakers for my laptop/mp3/etc and so my idea was to find a way to add a stereo audio input to the amplifier board so that I only had to plug a regular headphone output to it.
The HiFi has a dedicated board for amplifying the audio signals, drive the speakers and handle the radio system. I found the two traces in the PCB which carry the radio audio signals prior to be amplified and I disconnected them and made a simple board with a DPDT relay to switch between the existing radio signal or my external headphone signal. The problem is that when I switch to the external signal (coming directly from an MP3 stereo jack) the volume is really low and barely audible.
The PCB trace comes from a DC-blocking capacitor which is connected to the radio IC. I have no clue of its output impedance or the input impedance of the adjacent amplifier...
At first I thought the problem was the voltage level, but it's not. If I plug in my Android mobile, which happens to have a higher level, I can certainly hear distortion at higher volumes. Besides, the voltage levels when the radio is connected are pretty much the same. So I guess the issue must be related to unmatched impedances then? What do you think?
Thanks in advance!!