Having had an opportunity to test Onkyo TX-NR555 vs Pioneer Elite SC-LX904, I’d like to share my impression here to facilitate your choice of a new AV receiver.
The number of channels for receivers is different - 7.2 versus 11.2, respectively, for devices. In terms of power, there are differences, the TX-NR555 has such a ratio W/Ohm - 130/6, while the Elite SC-LX904 has a power of 140/8. A common feature for devices is the same total harmonic distortion - 0.08%.
The manufacturer installed different DACs, the TX-NR555 received the model Hi-Grade 384 KHz/32-bit, but the Elite SC-LX904 is equipped with ES9026PRO 384 KHz/32-bit. Each of the compared opponents supports Bi-amping. Both Onkyo TX-NR555 and Pioneer Elite SC-LX904 can transmit an audio signal directly to the amplifier and bypasses any DSP processing.
These units have the same Wi-Fi modules. Each of the receivers has a Bluetooth connector. The contenders have differences in the supported services from Apple - AirPlay versus AirPlay, AirPlay 2 respectively. Access to the Spotify service is on each of the competitors. Most popular streaming services are available for our models under consideration - Deezer, TIDAL, Pandora. The quality of 4K/60Hz signal remains unchanged when transmitting from a source to a TV or projector via HDMI for both receivers. Signaling over HDMI in standby mode can provide the TX-NR555 and the Elite SC-LX904. Video scaling is only possible with the Elite SC-LX904. Operation with the Dolby Vision is only possible with the Elite SC-LX904.
The number of HDMI inputs/outputs varies depending on the receiver, the TX-NR555 has 6/1, and the Elite SC-LX904 has 7/3. HDMI Audio Return Channel is implemented in both devices. HDMI eARC is only supported by the Elite SC-LX904. When comparing receivers, it becomes clear that each of the rivals can work with HDMI CEC. The TX-NR555 has support for the standard HDCP 2.2, compared to the Elite SC-LX904, which supports the standard HDCP 2.3. Like most receivers, our models have a built-in phono stage for connecting a vinyl player.
Unlike the TX-NR555 where 2 Multi zones is provided, the Elite SC-LX904 works with 3 Multi zones. There is an ECO mode in TX-NR555. The Pioneer Elite SC-LX904 can be properly configured using the setup assistant.
A Dolby Atmos multichannel audio format is available both models. A DTS:X surround technology is supported by devices from our comparison.