To get informed with the specs of the receivers, we suggest you read the Denon AVR-S640H and Yamaha RX-A4A review. According to the results of our review, Denon AVR-S640H received 6.2 points out of 10 possible, and Yamaha RX-A4A was rated 8.7 points. The release date of AVR-S640H is 2018, and RX-A4A is 2021. This review shows us that the RX-A4A is a better choice as a home AV receiver than the AVR-S640H.
For the built-in amplifier, the devices received different marks - 6 and 8, respectively, on a 10-point scale.
The number of channels is equal to the number of possible connected speakers. The Denon AVR-S640H supports 5.2-channels sound, but Yamaha RX-A4A supports a 7.2-channels configuration.
RMS stands for the actual power of the receiver. The higher this value, the louder the sound can be produced. The differences between the models in terms of RMS power are significant - for the RX-A4A this value is 110/8 W/Ohm, and for the AVR-S640H it is 75/8 W/Ohm.
|Stereo power (RMS), W/Ohm||75/8, 100/6||110/8|
|Output impedance, Ohm||8, 6||8|
|THD in stereo, %||0.08||0.06|
After reviewing the audio features of each model, we can rate the AVR-S640H 6 out of 10, and the RX-A4A - 9.
Bi-amping is the amplification of one speaker with two amplifiers. This amplification method has a positive effect on sound quality. Bi-amping is possible on the RX-A4A.
Most receivers now come with a microphone included. It is with the help of this microphone that the auto-calibration system functions, which adjusts the sound of the receiver to the room.
|Digital to analog converter (DAC)||192 KHz/32-bit||384 KHz/32-bit|
|Pure direct (straight)||✔||✔|
|Auto speaker calibration||Audyssey MultEQ||YPAO|
|Speaker A/B switching||✖||✖|
|Other audio features||Audyssey Dynamic Volume, Audyssey Dynamic EQ, Compressed Audio Restorer, Hi-Res audio||CINEMA DSP 3D, Compressed Music Enhancer, Virtual CINEMA FRONT|
The connectivity of competitors in our comparison is markedly different, Denon AVR-S640H scored 7, and Yamaha RX-A4A scored 9 out of 10.
Bluetooth connection is now one of the main communication protocols for the receiver's control or even music broadcasting.
|USB||1 (USB 2.0)||1 (USB 2.0)|
Now music streaming services are gaining more and more popularity. They allow users to listen to millions of songs by subscription.
|Apple Music (AirPlay)||AirPlay, AirPlay 2||AirPlay, AirPlay 2|
|Other streaming services||Deezer, TIDAL, Pandora, Napster, SiriusXM, TuneIn Radio, iHeart Radio, Sound Cloud||Deezer, TIDAL, Pandora, SiriusXM, Napster, SoundCloud|
The presence of many connectors makes the receiver more versatile. But there are also narrowly targeted models, the number of connectors which are limited to a certain area of use. And when choosing their own receiver, users need to consider exactly your goals for using the receiver. For extensive connection, Denon AVR-S640H got 6 points, but Yamaha RX-A4A received 8 points.
Denon AVR-S640H is equipped with 5/1 HDMI inputs and outputs, and Yamaha RX-A4A has 7/3 HDMI inputs and outputs.
HDMI eARC is the next step in the development of audio return channel technology, which works in conjunction with HDMI 2.1. Using eARC provides the highest sound quality for home audio systems. HDMI eARC is available on Yamaha RX-A4A.
The HDCP encryption protocol is now mandatory for most media devices. This security technology encrypts digital signals from one product to another. HDCP content-encryption protocol is present on Denon AVR-S640H in the HDCP 2.2 version, and Yamaha RX-A4A has the HDCP 2.3 version.
|HDMI ARC (Audio Return Channel)||✔||✔|
|HDMI eARC (Enhanced Audio Return Channel)||✖||✔|
|Digital content protection (HDCP)||HDCP 2.2||HDCP 2.3|
|Subwoofer output (LFE)||2||2|
|Headphone output||1 x 6.3||1 x 6.3|
|Optical digital input||2||2|
|Coaxial digital input||1||1|
|Phono (MM) input||✔||✔|
|Front panel connectors||USB, phones, setup mic||USB, phones, setup mic|
|Multi channel preamp output||✖||✔|
The AV receiver is the heart of the home theater. And in this case, support for all current video formats ensures the best user experience, so it is very important to consider this when choosing a device. Video features of the AVR-S640H were rated 6 out of 10 against the 8 for the RX-A4A.
With the 4K pass-through feature, the AV receiver sends "native" 4K signals to a 4K TV from a video source without any processing. The AVR-S640H works with the 4K/60Hz video, and the RX-A4A has the 4K/120Hz.
The AV receiver passes "native" 8K signals from a video source to 8K TV without any encoding, with the 8k pass-through features. The 8K path-through is available on Yamaha RX-A4A.
Most of the AV receivers have a video scaling function, it is the process of reformatting the video signal to a higher resolution without losing the quality of the image. Upscaling the video signal resolution is possible with Yamaha RX-A4A.
|HDR (High Dynamic Range)||✔||HDR10+|
|4K signal pass-through||4K/60Hz||4K/120Hz|
|8K signal pass-through||✖||8K/60Hz|
|HDMI signal pass-through||✔||✔|
|3D signal pass-through||✔||✖|
|HDMI pass-through in standby mode||✔||✔|
|Analog to HDMI scaling||✖||✖|
|HDMI to HDMI scaling||✖||✔|
|Other video features||BT.2020, HLG||x.v.Color, HLG, BT.2020, LipSync|
In terms of evaluating additional features, both receivers received a score of 10 out of 10.
|Voice control||Amazon Alexa, Google Assistant, Siri, Josh.AI||Amazon Alexa, Google Assistant, Siri, Josh.AI|
|App control||iPhone, iPad, iPod, Android||iPhone, iPad, iPod, Android|
|Display||colour OSD||colour OSD|
|Tuner||AM, FM||AM, FM|
|Auto power off||✔||✔|
|Graphical user interface (GUI)||✔||✔|
|Firmware update||network, USB||network, USB|
|Other additional features||IP Control, Web Control||Web Control, App Control|
As the center of a home media system, each multichannel receiver has an additional set of terminals for connecting the second set of speakers to create additional audio space in Zone 2 or even Zone 3 where audio can have the separate source.
|Multi-room zones||has not||2|
|Zone audio output||has not||preout|
|Zone HDMI output||has not||✔|
|Multi-room control||has not||MusicCast|
|Remote control input/output (IR)||0/0||1/1|
|DC trigger output (12V)||0||2|
Denon AVR-S640H got 5 points for the multichannel surround sound and Yamaha RX-A4A got 7.
Dolby Atmos' particularity is that this is the object-oriented sound format, that is, each audio signal object is independently sounded and connected to its spatial position. Yamaha RX-A4A can create 3D sound due to the Dolby Atmos support.
DTS:X is an algorithm used by the processor to create sound scenes, where sounds connected directly to objects rather than channels, and to determine the optimum sound output distribution in space. Surround sound with DTS:X is available on the RX-A4A.
|Dolby (other)||Dolby Digital Plus, Dolby Pro Logic||Dolby Digital Plus, Dolby Atmos Height Virtualization|
|DTS HD Master||✔||✔|
|DTS (other)||DTS 96/24, DTS-HD, DTS-EXPRESS, DTS-Surround, DTS Neo:6||DTS-ES, DTS-HD|