It makes sense comparing Onkyo TX-RZ830 vs Yamaha RX-V485 because they both are able to give some premium features.
A significant difference between the receivers in the number of channels, Onkyo TX-RZ830 has 9.2 versus 5.1 for Yamaha RX-V485. Regarding power, then TX-RZ830 has such a W/Ohm ratio - 180/6 when RX-V485 has a power of 80/8, 145/6. The THD is 0.08% for the TX-RZ830 but 0.09% for the RX-V485.
Characteristics of digital to analog converter (DAC) are different, AK4458 384 KHz/32-bit for TX-RZ830 and Burr-Brown 384 KHz/32-bit for the RX-V485. Both the TX-RZ830 and the RX-V485 support Bi-amping. Each of the AV receivers can transmit an audio signal directly to the amplifier and bypasses any DSP processing. Rivals from our review have Bluetooth support. The Onkyo TX-RZ830 has support for AirPlay, and its competitor in our comparison - AirPlay, AirPlay 2. Spotify can be used on each receiver. The TX-RZ830 can work with the audio stream from Deezer, TIDAL, TuneIn Radio, and the RX-V485 can receive a content from Deezer, TIDAL, Pandora, Napster, SiriusXM.
Both AV receivers support HDR10 technology (High dynamic range). 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. The RX-V485 can scale the input HDMI signal, unlike the TX-RZ830. The HDR standard - Dolby Vision is supported by these receivers.
The Onkyo TX-RZ830 has 7/2 HDMI inputs/outputs versus 4/1 HDMI connectors of the Yamaha RX-V485. The HDMI Audio Return Channel (ARC) feature supports both devices. The HDMI eARC is available only on the RX-V485. The Consumer Electronics Control (CEC) feature is present in most modern AV receivers and the models in our comparison are no exception. The TX-RZ830 supports the protection of digital content of the standard HDCP 2.2, versus HDCP 2.3 in the RX-V485. The TX-RZ830 has a built-in phono stage for connecting a vinyl player.
The TX-RZ830 supports 3 Multi-room zones, versus 2 for the RX-V485. The TX-RZ830 supports voice control via Google Assistant, and the RX-V485 - Amazon Alexa, Google Assistant, Siri. An ECO mode is only available for the RX-V485. Both TX-RZ830 and RX-V485 can be configured using the Setup assistant.
Only the TX-RZ830 has a Dolby Atmos multichannel audio format support. A surround technology DTS:X is supported only by the TX-RZ830.