I hadn't played with the EQ settings in a while and opened it up just now to find that an update has added numeric values to the sliders, allowing them to be set accurately. This is great, thanks Andre! Looking through the changelog I assume this happened in build 839. If anyone's interested, it looks like the Q value for the filters is 1.5. This is necessary info if you're looking to model the EQ in another app in order to match the response to a target curve. I measured this the same way as described above and found the effect of the 1kHz band was 3dB down at 1.3kHz
I was trying to find this out myself, and after doing some searches it seems this question has been around for a while. So I decided to do an experiment and find out the EQ steps for myself. Executive summary: each step in the EQ (by tapping above or below the slider) is 1.5dB Details: Poweramp full version v3-build823 All audio processing done in Adobe Audition I created a 24/48 flac file containing a -20dB pure 1kHz tone in Audition then played in in Poweramp on my phone and routed the headphone out to the line-in on my motherboard. Then I recorded the output from Poweramp while changing the 1kHz EQ silder. After recording each step in the EQ I analysed the volume using Audition amplitude statistics and noted down the total RMS amplitude for each segment. Here's the results: Step level difference 0 -22 0 1 -20.5 1.5 2 -19 3 3 -17.5 4.5 4 -15.99 6.01 5 -14.49 7.51 6 -12.99 9.01 7 -11.49 10.51 8 -9.99 12.01 9 -8.49 13.51 10 -6.99 15.01 -1 -23.51 -1.51 -2 -25.01 -3.01 -3 -26.45 -4.45 -4 -27.95 -5.95 -5 -29.45 -7.45 -6 -30.95 -8.95 -7 -32.38 -10.38 -8 -33.88 -11.88 -9 -35.38 -13.38 -10 -36.88 -14.88 The slight drift seen from step -7 down may simply be due to non-linearity in my recording setup and is not significant. As you can see, the maximum range is +/-15dB and this is broken into 10 equal 1.5dB steps.