[Elecraft] Usb-lsb audio tone - Mike iw3smr-Italy

[mic b]

Hi, I'm an OM from Udine, northern Italy.  I own a K3 and I noticed that
changing the mode from Usb to Lsb the audio tone varies slightly.  It's
normal?  The five-pole filter has the center frequency set correctly as per
the label.  Is it possible to vary the carrier frequency of the sidebands?
Thanks for the answers and greetings to all.  '73 de Mike iw3smr