I just got a pair of DSP-33s and they were running fine. Then I upgraded and they were popping. Then I hard Reset them and the popping went away.

Check Cables
Check Levels
Check Firmware
Check everything is in a clean state (i.e. reset/type).

P.S. What's a 568.25?

- Fiddler (IMHO)

If you think listening to music is fun, try learning an instrument.
HT: G61RSL, 4x5K, 5.5KHC, 2xSC6000, Transporter, HD621, Philips BDP7501 4K, Tivo, 65" LG OLED 4K C6
Computer: Foobar2000, 5K, Mojo, HiFiMan HE1000 V2