It makes sense comparing Denon AVR-S640H vs Marantz NR1509 because they both are able to give some premium features.
Considered AV receivers have the same number of channels 5.2. Regarding power, then AVR-S640H has such a W/Ohm ratio - 75/8, 100/6 when NR1509 has a power of 50/8, 60/6. The THD is the same and is 0.08%.
Characteristics of digital to analog converter (DAC) are different, 192 KHz/32-bit for AVR-S640H and 192 KHz/24-bit for the NR1509. None of the models 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 Apple Music service is implemented on considered devices: AirPlay, AirPlay 2. Spotify can be used on each receiver. The AVR-S640H can work with the audio stream from Deezer, TIDAL, Pandora, Napster, SiriusXM, TuneIn Radio, iHeart Radio, Sound Cloud, and the NR1509 can receive a content from Deezer, Pandora, TuneIn Radio.
These units support HDR technology. 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 Denon AVR-S640H has 5/1 HDMI inputs/outputs versus 7/1 HDMI connectors of the Marantz NR1509. 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. These compared receivers have a built-in phono stage for connecting a vinyl player. Supported voice control technologies are identical - Amazon Alexa, Google Assistant, Siri, Josh.AI. It is also worth noting that the ECO mode is presented in each of the receivers. Both AVR-S640H and NR1509 can be configured using the Setup assistant.
None of the rivals equipped with Dolby Atmos multichannel audio decoder. The receivers do not support the surround sound technology DTS:X.