When we convert it to dB, it is negligible - for example, the "rise" on 10kHz vs. 1kHz (2,256V - 2,24V) is just 0,06dB! If we included possible measuring errors and equipment accuracy...it is flat! It is good info - basically, nothing bad (frequency response wise) happened by the grid-choke. If it sounds good on your speakers like it measures...congrats. Post your other findings - larger output, etc. Thanks!