Sony CDP-M95 line input modification for headpone amp question

[versusliveact]

Hi Everyone!

I am a hobbyist in electronics world.
I have one Sony CDP-M95, It have headphone amp and I really like the sound of it, unfortunately it have no line input,
so I thinking about the modification,I can see from the schematic, the Audio board have 7 pin input,

the 7 is a right channel audio
the 5 is a ground
the 3 is a left channel audio

I tried soldier a stereo jack socket to those pins,and the input is working but activated only when I put a CD in and pressed the play button,and I can hear the CD music,and the line in at the same time.Ok I could write a 70 minutes empty CD,but maybe have a more elegant solution for this.

The CD player section is not important for me,I would like to use just the headphone amp mainly.

If You have any advice,how to do this,it would be great!

Thank You!

Best wishes!

Lac


The full Schematic is here: https://elektrotanya.com/sony_cdp-m95_sm.pdf/download.html
The Audio and headphone section is here:

 

[skywaveTDR]

Just supply the 1 and 3 terminals of the Headphone amp input with a signal with a 10K resistor in series and both commons of the input to pin 2. You do not need all that other circuitry before the headphones and the reason it mutes is because of the mute line pin 2 of that connector. Adding the input to the headphone amp through those 10K resistors is like creating a mixer. The NJM4556 might5 not have that much drive and I have put LM386 into tape decks when the amps they used for the headphones were noisy being speaker amps with gain wide open. The Tascam 52 has a very much better headphone amp circuit in it with low noise op amp and transistors for current drive. Even a hobbyist should be able to build a headphone amp using a proto board, some pots and LM386 or a like chip. The power supply I would select is 12 Vdc with an additional 1000uFd 16V caps for good filter of supply. Yes, I am a BSEE so the advice should be accurate plus I have probably worked on that CD player at one time over 47 years- I did work at Sony for a while.