Output Impedance Switching Benefits

[Loquah]

I hadn't previously realised that the Mainline has an output impedance switch and it has me wondering now, why this is necessary? My previous understanding was that lower is always better. When is that not the case?

[Paul Birkeland]

Lower impedance taps deliver better damping and noise performance into high impedance loads, but at reduced power. If you have power hungry headphones, the higher impedance setting will give better performance.

[Loquah]

OK. Thanks Paul.

I guess it depends on how the output impedance is implemented then. The iRiver AK100 portable DAP has a 22ohm resistor on the output circuit which is completely redundant from a performance perspective (by all accounts and my personal experience). Does the Mainline OI switch just add impedance with a resistor or is it a output transformer winding? (I haven't gotten to that stage of the build yet)

[Paul Birkeland]

A 22 Ohm resistor at the output would be to shed some VT age and improve the noise floor. This would come at the expense of power and damping.

The Mainline switches the actual transformer impedance, no resistors are used.

[Loquah]

Great. Thanks for the explanation!