CKKeung,
May be you can consider the " Interocitor " transformer . They have a model that perhaps can solve your impedance mismatch :
# Unity-gain (1:1) and impedance conversion (4:1) models available.
# 4:1 model acts as impedance converter for driving long interconnects.
# 4:1 model offers transparent attenuation for high-gain systems.
Gary Koh started a very interesting thread on it: RMAF: The Interocitor Saved My Life
http://www.whatsbestforum.com/showthread.php?4248-RMAF-The-Interocitor-Saved-My-Life
May be you can consider the " Interocitor " transformer . They have a model that perhaps can solve your impedance mismatch :
# Unity-gain (1:1) and impedance conversion (4:1) models available.
# 4:1 model acts as impedance converter for driving long interconnects.
# 4:1 model offers transparent attenuation for high-gain systems.
Gary Koh started a very interesting thread on it: RMAF: The Interocitor Saved My Life
http://www.whatsbestforum.com/showthread.php?4248-RMAF-The-Interocitor-Saved-My-Life