Want to mention it on earfilter.org? That would also help me find out if everything is working as it should on there. Among other things, I’m not sure how “locked down” the site should be. Because I don’t have a team of bot-wielding spam fighters at my disposal, I’m inclined to require registration for editing, and I’ve enabled reCAPTCHA, but I’m no MediaWiki guru so I’m not sure it’s working as planned yet. If you have a mo, please let me know x spk

Essentially it comes down to two things: the choice of algorithms that is available, and the input connections. Most of the portable audio processors I’ve seen either have microphone or guitar (Hi-Z) inputs.

Let’s take the Korg Pandora as our example. In this case, the input is mono, and Hi-Z. The best we’d be able to do with this would be to add an impedance matcher to the input and short in the live signals of both channels of our hi-fi’s line-level output. This would give us a clean enough mono signal, but it would destroy the stereo image of the source recording. For a first attempt at an earfilter hardware device, that might not matter, but then consider the algorithms available. I expect we’d need at least a four-band dynamics processor and a six-band parametric EQ in order to get useful results, and the Pandora, if I’m not mistaken, features neither of these.

If we find a portable device with a stereo line input that’s capable of running those algorithms, then maybe we need do nothing further. But I don’t know of any such device yet.

On the other hand, the earfilter might be able to function as an open-source Pandora, with the simple addition of an impedance-matching mono input and a few good free amp-sim & FX plugins.