Sony STR-ZA3100ES vs Onkyo TX-RZ840 comparison definitely makes sense.
A significant difference between the receivers in the number of channels, Sony STR-ZA3100ES has 7.2 versus 9.2 for Onkyo TX-RZ840. Regarding power, then STR-ZA3100ES has such a W/Ohm ratio - 70/8, 90/6 when TX-RZ840 has a power of 180/6. The THD is 0.09% for the STR-ZA3100ES but 0.08% for the TX-RZ840. Both the STR-ZA3100ES and the TX-RZ840 support Bi-amping. Each of the AV receivers can transmit an audio signal directly to the amplifier and bypasses any DSP processing.
Only the Onkyo TX-RZ840 can connect to the Internet via WI-FI. Rivals from our review have Bluetooth support. Only the TX-RZ840 supports Spotify. Compared AV receivers retain the quality of 4K/60Hz signal when transmitting from a source to a TV or projector. HDMI signal transmission in standby mode is implemented in each of the devices. Both competitors are not able to scale the HDMI signal. The HDR standard - Dolby Vision is supported by these receivers.
The Sony STR-ZA3100ES has 6/2 HDMI inputs/outputs versus 7/2 HDMI connectors of the Onkyo TX-RZ840. The HDMI Audio Return Channel (ARC) feature supports both devices. HDMI eARC is available in each model. The Consumer Electronics Control (CEC) feature is present in most modern AV receivers and the models in our comparison are no exception. Both models support the standard HDCP 2.2. The TX-RZ840 has a built-in phono stage for connecting a vinyl player.
The STR-ZA3100ES supports 2 Multi-room zones, versus 3 for the TX-RZ840. An ECO mode is not present in each of the AV receivers. Both STR-ZA3100ES and TX-RZ840 can be configured using the Setup assistant.
Both devices have support for Dolby Atmos multichannel audio format. The surround sound technology DTS:X is supported by devices under review.