Looking up and reading reviews of the Infinity Basslink (mentioned in a recent post) where they mention it takes either line or speaker level inputs, reminded me to post on this topic.

I realized recently that using speaker-level to line-level adapters wasn't as wasteful of current as I'd assumed off the bat: I'm pretty sure that the high impedance of the units means that the speaker outs aren't actually flowing much current at all, so the head unit or amp that is feeding the adapters isn't using as much current, nor generating as much heat, as it would be were it feeding 4 ohm speakers. Right?

I assume that there are other caveats. Something along the lines of increased distortion, etc. Any comments or pointers to good articles on the topic?

-brendan

Heat is not a concern with using line level adaptors. The only real downside for using them is the increase in distortion. The signal has to travel thorugh the internal amplifier of the radio first. With all amps, there is a small amount of distortion added. When you use a line level adaptor, it limits the output voltage so that the external amp isn't being overdriven. The original signal will still have distortion present, but now you're amplifying it even more and adding additional distortion from the other amp. For a cleaner sounding install the factory amp should be ditched and a new amp using line-level in should be used. If your new radio has RCA outputs, you can also use RCAs with the ends cut off and wired directly to the factory amp's input wires. The only problem with this is that the factory amps gains may not be properly matched to the level of output from the new radio. Just remember: "garbage in-garbage out".