Contour 1.3.3 makes the FiiO KA15 play exactly the curve and preamp you see.
- Shelf filters. The KA15 plays LOW SHELF and HIGH SHELF with a Q 1.41 times (√2) lower than the value it stores. A shelf sent with Q 0.71 sounded like Q 0.50 - a wider, softer slope than the graph showed. Peak filters were already right. Contour now stores shelf Q x 1.41 and divides by 1.41 when it reads the KA15, so you hear the shelf on the graph - the one squig.link and AutoEQ profiles describe.
- Preamp. Every USER preset on the KA15 plays 12 dB quieter than EQ off, on top of its own preamp: a profile with preamp -4 dB played 16 dB below EQ off. Contour now adds those 12 dB back when it writes the preamp, so PREAMP in Contour is the real level against EQ off. On the KA15 it goes from -24 to 0 dB. Leave it on AUTO, so the curve never goes above 0 dB.
- Send your KA15 profiles again after updating. Profiles sent with 1.3.2 read back with the shelf Q and preamp the KA15 actually played, so they lose ON DAC until you send them again.
- The FiiO app shows other numbers. The FiiO app and FiiO's EQ web page show the stored values, so there a shelf reads 1.41 times higher in Q and the preamp 12 dB higher than in Contour. That is expected.
- Shelf Q up to 7.07 on the KA15, because the stored value stops at 10. Contour blocks sending a sharper shelf and says why.
Measured on a KA15: a sweep through the dongle into a PC line-in, each result compared with EQ off - four shelves at different frequencies, gains and Q values, and six preamp settings. After the change, a profile sent from a phone matched Contour's graph within 0.03 dB and its preamp within 0.01 dB. Details in PROTOCOL.md.
The shelf problem was measured and discussed on Audio Science Review. Thanks to u/bootymeister on Reddit for pointing it out.
Updating from 1.3.2 keeps your profiles.
SHA-256 of contour-1.3.3.apk: 1d918da9e79518e70f161335dcb319fcae8cd9f691326d3438743d111c6c1cea
Signed by CN=Chronosaur, certificate SHA-256 c8c8caea761628ed9d505ff07342ee5ea0d466a4ad718d0db077422ba3f7e601.