An affordable AV receiver is always a good option to consider, so Onkyo TX-NR555 vs Onkyo TX-SR393 comparison definitely makes sense.
A significant difference between the receivers in the number of channels, Onkyo TX-NR555 has 7.2 versus 5.2 for Onkyo TX-SR393. Regarding power, then TX-NR555 has such a W/Ohm ratio - 130/6 when TX-SR393 has a power of 80/8, 155/6. The THD is the same and is 0.08%.
Characteristics of digital to analog converter (DAC) are different, Hi-Grade 384 KHz/32-bit for TX-NR555 and AKM 384 KHz/32-bit for the TX-SR393. Only the TX-NR555 supports Bi-amping feature. The Onkyo TX-NR555 can transmit an audio signal directly to the amplifier and bypasses any DSP processing. Rivals from our review have Bluetooth support. Only the TX-NR555 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. The TX-SR393 can scale the input HDMI signal, unlike the TX-NR555. Dolby Vision technology found support only on the TX-SR393.
The Onkyo TX-NR555 has 6/1 HDMI inputs/outputs versus 4/1 HDMI connectors of the Onkyo TX-SR393. The HDMI Audio Return Channel (ARC) feature supports both devices. Unfortunately, HDMI eARC is not available on monitored devices. 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-NR555 has a built-in phono stage for connecting a vinyl player.
Each of the AV receivers from our review supports 2 Multi-room zones. A voice control is not available. An ECO mode is only available for the TX-NR555. Unfortunately, the setup assistant is not available in each of the models.
Both devices have support for Dolby Atmos multichannel audio format. The surround sound technology DTS:X is supported by devices under review.