An affordable AV receiver is always a good option to consider, so Denon AVR-S640H vs Denon AVR-S740H comparison definitely makes sense.
A significant difference between the receivers in the number of channels, Denon AVR-S640H has 5.2 versus 7.2 for Denon AVR-S740H. Regarding power, then AVR-S640H has such a W/Ohm ratio - 75/8, 100/6 when AVR-S740H has a power of 75/8, 110/6. The THD is the same and is 0.08%.
Competitors' digital to analog converter (DAC) is identical to 192 KHz/32-bit. 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.
Both models have the ability to connect to the Internet via WI-FI. 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. Deezer, TIDAL, Pandora, Napster, SiriusXM, TuneIn Radio, iHeart Radio, Sound Cloud - all of these streaming services have found application in each of the models.
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 6/1 HDMI connectors of the Denon AVR-S740H. 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 AVR-S740H can be configured using the Setup assistant.
Only the AVR-S740H has a Dolby Atmos multichannel audio format support. A surround technology DTS:X is supported only by the AVR-S740H.