Super simple, manual, why?!
PRMP really good, two switchable between a switch (or one in the CAR or the other jack) 4 dual outputs (ie power supply of 8 headphones!) With an output for each volume. Equa hi & low for the main entrance
I use it for the past six years, without any concern, the sound is clear, to me it is the top of the market, unfortunately, little known trs! nine silent in the price of 300 euros in 2000