To cut the long story short, I've been trying to transcode some higher-bitrate files (which are either an overkill for my iAudio X5, or are unsupported on it), and I've been experimenting with impulse_noisetune and impulse_trigger_profile switches in the oggenc2.

Since I can ABX the transcoded file in 99% cases, but those with impulse_x switches sound a little more pleasant to the ears, can someone confirm that the latter is not a placebo effect? And if so, Can you reccommend me how to use those switches (I am trying to move around bitrates of 128, 144, 160 kbps)?

Many thanks.

(edit: typos only)

iAudio X5 is supposed to support at the very least -q1 to -q10, so you shouldn't need to transcode for that reason.

That's not the reason. The main reason are the high-bitrate files in an unsupported format, such as AAC or MPC (yes I am aware of the new Rockbox, but for now I'd like to stick with the original firmware for more than one reason).
The less-important reason is that I move through noisy places a lot, so a medium-quality is sufficient for my portable audio. This also means that I'd be able to store more music, so I wouldn't have to delete stuff that often.

Any ideas for my question posted earlier?
Thanks.

Oh, I'm sorry, I thought you meant you were transcoding high bitrate Vorbis files.
Nevermind me!

I don't really know anything about the impulse options, though you can always try screwing around with them and ABXing between that and a "normal" transcode.

It's on the Recommended Ogg Vorbis page in the wiki how to use them. Don't play around with the trigger profile. If you increase the trigger profile the bitrate will spike dramatically, it's only use for microattacks. If you are trying to control pre-echo or sharp attacks use the impulse_noisetune switch. That is hard-wired directly into the noise biasing curves and can make a small / large improvement on differents types of music, etc. I personally would just perform ABX testing to see if you can hear the difference. What are you transcoding too? are you transcoding Vorbis files down to a lower -q?

Actually, I am transcoding mostly from hi-bitrate MPC. As I said, both are ABXable, and I can hear the difference. I think I'll just play around with those since they are for my personal use and keep those that sound more "listenable" to me.

Thanks.