One common cause of Pocket Operator sound differences is incorrect signal balance. By default, Pocket Operators are configured to receive signals from both the left and right channels. If you are sending a mono signal (only one channel is being recorded), then your Pocket Operator will not hear any input from the other channel and will output only the mono signal.
If you want your Pocket Operator to also output signals from the other channel, you can simply turn off Left/Right Mode in Settings ▸ Audio & Mics. However, be aware that doing this will add extra noise (multitrack audio synchronization) since both channels will now be outputting simultaneously.