어테뉴에이터 - 헤드폰 출력을 마이크 단자에

어테뉴에이터 

- 헤드폰 출력을 마이크 단자에

- 스피커 출력을 라인인 단자에

Connecting 

speaker signals

to line level inputs

http://www.epanorama.net/circuits/speaker_to_line.html

Line level signal 

to microphone input adapter

http://www.epanorama.net/circuits/line_to_mic.html

40 dB PAD

Consumer audio line (-10dBu) level to microphone matching can be done using a "40 dB L-pad attenuator". This circuit is indeed quite simple:

+Line level input -----R1----+-- +Mic level output
                             |
                  +----R2----+
                  |
Ground (input)----+--------------- Ground (output)

R1 = 10 kohm
R2 = 100 ohm