An affordable AV receiver is always a good option to consider, so Denon AVR-S660H vs Denon AVR-X3800H comparison definitely makes sense.
A significant difference between the receivers in the number of channels, Denon AVR-S660H has 5.2 versus 9.4 for Denon AVR-X3800H. Regarding power, then AVR-S660H has such a W/Ohm ratio - 75/8, 100/6 when AVR-X3800H has a power of 105/8, 135/6. The THD is the same and is 0.08%.
Competitors' digital to analog converter (DAC) is identical to 192 KHz/32-bit. Only the AVR-X3800H supports Bi-amping feature. The Denon AVR-X3800H can transmit an audio signal directly to the amplifier and bypasses any DSP processing.
WI-FI modules have the same characteristics: 2.4/5GHz. 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-S660H can work with the audio stream from Deezer, TIDAL, Pandora, SiriusXM, Napster, SoundCloud, and the AVR-X3800H can receive a content from Deezer, TIDAL, Pandora, SiriusXM, Napster, SoundCloud, Amazon Music, Amazon Music HD, MOOD:Mix.
Both AV receivers support HDR10+ technology (High dynamic range). Compared AV receivers retain the quality of 4K/120Hz 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 rivals can scale the resolution of the incoming HDMI signal. The HDR standard - Dolby Vision is supported by these receivers.
The Denon AVR-S660H has 6/1 HDMI inputs/outputs versus 6/3 HDMI connectors of the Denon AVR-X3800H. The HDMI Audio Return Channel (ARC) feature supports both devices. HDMI eARC is available in each model. 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 2.3. 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-S660H and AVR-X3800H can be configured using the Setup assistant.
Both devices have support for Dolby Atmos multichannel audio format. The surround sound technology DTS:X is supported by devices under review.