[shafu]

If the adapter cable just has greater impedance, wouldn't it be possible to have that built into an amp? I figure since one would only use the adapater cable with an amp, why not have the amp already have that built in?

I've tried to do a search on this, but couldn't find any reference...

 

[thomas]

Yep, it should be possible...

To my knowledge, the 4p-4s convertor cable is nothing more than a 73 ohm resistor in series with the output.

just use a dpdt switch to switch the resistor on/off... If you calculate the values correctly you can add a 3rd impedance level, i built an amp for someone that adjusts between 0 ohms (highest damping factor), 73 ohms (ety 4p conversion), and 120 ohms (international standard)