What's the difference between the front and rear headphone jacks on the Symphony Desktop?

Connect low-impedance headphones to the rear 1/8" jack, and high impedance headphones to the front 1/4" jack.

The Symphony Desktop headphone output jacks utilize a unique Zero Ohm impedance circuit. Read more about this special circuit here:

https://apogeedigital.zendesk.com/hc/en-us/articles/360053665773-Symphony-Desktop-FAQ-s#h_01EKZW6NN545CKEXXBDE3EFQSB