AV Processor Checklist Definitions

Interface and Setup

On Screen Display
This indicated the presence of a text-based user interface to operate and configure the system.

Upgradeable Firmware
To obtain the full credit here the user has to have the ability to upload software updates to enhance performance, fix bugs, or add product features. This is usually done via RS-232, but can also be done via RJ45 or even a proprietary connection.

Programmable Learning Remote
While most processors and receivers come with a remote control that can be programmed to control other components, the device must have the ability to learn functions of other devices to get full credit. Remote controls that only work with pre-programmed codes, or which lack full learning functions, receive no credit. Remotes that feature learning, but are otherwise lacking in features (macros, backlighting, etc) may receive partial credit.

Discrete Source Multi-Room / Multi-Zone
Many receivers and processors can support some form of Zone 2 preamp output, but we want to make sure there is the ability to discretely select a different input for Zones 2 and/or 3. This means that you can listen to a DVD in the Main Zone while playing the tuner in Zone 2.

Assignable >150mA Triggers Bonus Feature
We're looking for multiple and assignable triggers per source, DSP mode, etc with at least 1 high current (>150mA) trigger. Partial credit is given for the presence of triggers (preferably more than one).

Windows-based Software Interface Bonus Feature
This feature indicates an ability to upload settings to a computer application or control panel for storage and/or changing of processor/receiver configuration.

Upgradeable Hardware Bonus Feature
This extends the firmware update ability to actually having the ability to perform physical hardware updates (via a dealer or the manufacturer) to enhance performance, fix bugs, or add product features and/or new A/V interfaces. Products with a history of “vaporware” should be considered non-upgradeable, even though they may receive points for this feature.

RS-232C Interface Bonus Feature
This is a standard interface approved by the Electronic Industries Alliance (EIA) for connecting serial devices for two way communications. The RS-232C interface is usually utilized for remote control of the processor/receiver or for providing firmware updates to the platform.

GUI Interface Bonus Feature
Here we look for the presence of a graphical user interface that uses animated or iconic navigation, much like the Windows operating system, for operating and configuring the system.

Assign Digital Inputs for > 1 Source Bonus Feature
When assigning digital inputs it is nice to have the ability to have audio from a single digital source function on more than one input. If the processor/receiver can do this without losing the initial assignment it passes.

Assignable Modes to Source Input or Signal Type Bonus Feature
Being able to assign Dolby Pro Logic IIx or DTS Neo:6 to a particular input, or Signal Type (DTS, Dolby Digital, or PCM for example) is extremely helpful and results in the ability to truly automate the process of getting the right mode for each situation. Processors that can assign Modes to each input and Signal Type (generally determined by bit rate and sampling frequency) will score full points, with partial credit for partial or quirky implementation.

Adjustable Turn-on Level Default Bonus Feature
The ability to have a fixed power up volume level will help users avoid being blasted by loud sound during system start up. This is especially helpful if your home theater is used by children or others in the household.

Routable Amplifier Channels (receivers only) Bonus Feature
This feature is for receivers-only and indicates an ability to re-route unused on-board amplifiers to another location. For example, if you have a built-in 7-channel amplifier, but are only listening on a 5.1 system, you can take the extra 2 amplifiers and use them to power Zone 2, passively biamp your main speakers, or drive an additional set of DSP ‘Presence’ or ‘Side Axis’ speakers.

Multi-room Surround Support Bonus Feature
This bonus feature means that the processor or receiver has multiple multi-channel outputs that can support more than one home theater Zone. For the processor to receiver full credit, these zones have to be fully independent and must also be fully configurable so that levels, group delay, etc can be configured in the second multi-channel zone.

Processing Features

6.1 / 7.1 EX/ES
Dolby Digital EX (DD EX) - Dolby Digital EX is based on Dolby Digital, but includes an extra “Surround Back” channel, making it a “6.1” format. This sixth channel is encoded as a matrixed signal within the standard left and right surround channels and is reproduced by either one or two additional surround speakers.

DTS ES - This enhanced version of the 5.1 DTS system adds a sixth channel which is either matrixed off of the left and right surround channels like DD EX or, in some cases (DTS ES Discrete), a discrete channel. Two rear “Surround Back” speakers are typically used to broaden the sound field, hence 7.1. Software is backwards-compatible with 5.1 systems, but requires an EX/ES processor to decode the extra channels. Neo:6, much like Pro Logic IIx, creates 7.1 from stereo or multi-channel program material.

PLII / PLIIx & Adjustable Features
Pro Logic II – This mode derives 5 full-range channels and subwoofer output from a two-channel source. It includes modes for Music and Movies and provides a more expansive or diffused sound that is makes good use of a system’s center-channel.

Pro Logic IIx – This mode takes Pro Logic II one step further by expanding 2CH and multi-channel sources to 7 channels. In more flexible processors, Dolby Pro Logic II and IIx can be overlaid on top of DTS or Dolby Digital soundtracks to intelligently make use of Surround Back channels.

DTS 96/24
96 kHz sampling rate recordings support higher frequency ranges during playback. The conventional Dolby Digital and DTS sampling rate is 48 kHz (or 44.1 kHz for PCM-encoded CDs). DTS 96/24 is fully compatible with existing DTS decoders, which will simply output 96/24-encoded tracks at 48 kHz.

The DTS coding system has a “core + extension” structure. The “core” represents the standard DTS data we are all familiar with from legacy devices. The “extension” carries data enhancements. The “extension” for DTS 96/24 carries the additional spectral data added by utilizing 96 kHz sampling. DTS 96/24 decoders read both “core” and “extension” and reproduce the extended spectrum. The data rate for 96/24 is ~1.5 Mbit/s as opposed to the typical ~754 kbit/s.

THX Select / Ultra 2 Bonus Feature
To achieve THX Certification, home theater products must meet or exceed THX performance requirements under "normal" playback functions. For receivers and controllers, THX adds patented post-processing features such as ReEQ, Timbre Matching, Adaptive Decorrelation, Adaptive Speaker Array and Boundary Gain Compensation. When a product switches video, THX tests it to guarantee that it does not degrade the signal (including HD if the product advertises that feature). THX Ltd. does not test for product longevity and does not test "custom" or "DSP" modes such as Cathedral, Sports and room compensation. Please see our THX Interview for more information about THX Certification.

DSP Enhancement Modes Bonus Feature
Digital Signal Processing modes can enhance or expand the sound field and/or simulate generic or specific concert arenas, churches, or a megaplex cinema. We grade the processors on having effective DSP modes that produce realistic or helpful options for music playback. Overly generic or unusable modes will rate partial credit, while a unit sporting effective, fully-configurable DSP algorithms will score full points.

Active Room Correction Bonus Feature
We are looking to see if the processor has an automated system that attempts to linearize the loudspeaker and room response via equalization and frequency shaping by analyzing test signals outputted from the speakers via the receiver to a calibration microphone. Partial credit will be given for systems that do not provide parametric EQ-based systems or that provide only cursory correction.

Notch Filter for Subwoofer Channel Bonus Feature
Nearly all listening rooms have bass modes or peaks that occur at the listening position. This features enables a processor or receiver the ability to tame the largest node by singling out that particular bass frequency and lowering its amplitude while not affecting a wide range of surrounding frequencies.

Automatic Calibration of Speaker Distances/Level Bonus Feature
Now found in an increasing number of even budget receivers, this is an automated system that determines the proper distance and level for all speakers. This is accomplished by analyzing test signals outputted from the speakers via the receiver to a calibration microphone (usually included with the processor or receiver).

Analogue Features

True Analogue Bypass
This is a “purist” feature which eliminates all unnecessary signal paths, turns off all video circuitry and processing, and avoids any analog to digital conversion stages when routing analogue input directly to an amplifier or amplifier section.

Digitally Controlled, Analog Volume
A handy feature, this signifies that volume control is regulated in the digital domain for greater precision, but audio signal remains analog for higher fidelity. “Logarithmic” volume control builds on this by varying the amount of volume change based upon the speed at which the volume knob is turned.

Digital Features

DAC Quality for All Channels
Our DAC (Digital to Analog Converter) rating considers the quality of the DAC (digital to analogue converter), reconstruction filters, and low pass filter structure. In general there is a short list of high quality DACs and the unit gets full credit if it uses one of these products.

Quad / Differential for Two-channel Mode
Implementing a differential / quad DAC arrangement can increase system linearity and lower the noise floor through a process of noise averaging and load sharing. If the processor has this it will get full credit for this bonus feature.

Supports Native DVD-A / SACD Decoding
Some processors and receiver have the ability to process high resolution formats with and without digital delay compensation and bass management. Some can also decode SACD in native DSD format. While it isn’t inherently bad to convert these formats to PCM before applying DSP and bass management, it is good to note any products that can do so natively.

Video Features

Component Video Upconversion
This indicates the ability to upconvert all composite and s-video inputs to component video. This does not mean that a composite signal output through the component connections will be of any better quality, but this at least allows for a single component connection to be made to a display. A single connection allows for complete A/V source switching. It is also helpful when processors and receivers can downconvert s-video to composite.

Lip Sync Delay
Due to increased video processing in digital displays, the video signal can often be delayed and become out of sync with the audio. The ability to add global audio delay to all channels to offset sync issues between audio and video is an important feature that corrects this problem. We prefer to see at least 0-100ms in 1ms increments.

BNC Connectors for Component Video Bonus Feature
BNC connectors provide a true 75-ohm video connection for video input and output as well as a solid, locking connection that is not enjoyed by the RCA-style connector. It is handy for the more high-end source components and displays that provide this type of connection.

Video Signal Pass-through When Off Bonus Feature
While a rare find, the ability to still pass analog video signals thru the processor even when turned off is a nice feature if you simply want to route a signal to your display without turning on the processor/receiver. This is very handy for those times you just want to allow guests or children to watch a source component and utilize the audio from a television or display device.

OSD Support for Component Video Bonus Feature
Full credit is given for processors and receivers that have the ability to utilize the On Screen Display (OSD) via the Component video outputs.

OSD Support for HDMI Video Bonus Feature
Full credit is given for processors and receivers that have the ability to utilize the On Screen Display (OSD) via the HDMI digital video outputs.

Analog to Digital Video Upconversion to HDMI Bonus Feature
Many of the newest mid-fi and high-end receivers and processors are adding HDMI switching. Upconversion from analogue component or other signal to digital (HDMI or DVI) output is much more rare. This feature allows a single digital connection to a display that can replay all video inputs to that single point of output – making for a very convenient one-cable connection. It is imperative that products that provide analogue-to-digital video conversion do so in a manner that does not degrade the source signal in order to receive full credit for this feature. Generally if this feature exists, the unit will also be able to display the OSD via the HDMI outputs (above).

Component Video Digital Processing Bonus Feature
Some receivers are able to perform scaling, color correction, noise processing, and deinterlacing on incoming analog video signals. Most systems provide upconverted 480p/576p/720p/1080i progressive-scan video output from connected interlaced 480i video sources, but do not provide greater than 480p output on copyrighted source material (like that present on most commercial DVDs). In this case, any input above 480i should be passed through the receiver without video processing or upconversion. This feature is most useful for analogue composite and s-video inputs.

Bass Management Features

Adjustable Crossover for LPF/HPF
An adjustable crossover delivers the ability to choose the proper crossover settings (i.e. between 40Hz – 150Hz) to best accommodate a wide range of speaker systems. The most flexible systems have 10Hz increments at the lowest frequencies.

Min 18 dB/oct LPF; Min 6 dB/oct HPF
This defines the rate of roll off for the receiver’s High Pass Filter (HPF) and subwoofer out Low Pass Filter (LPF). An octave represents a doubling or halving of frequency. Thus, if the speakers HPF is set at 80Hz with a slope of 24dB / octave, the signal to the speakers will be attenuated by 24dB for every halving of frequency (i.e. at 40Hz).

Subwoofer Output 2CH Stereo Mode
This means that the receiver allows the use of the subwoofer even for analogue or digital 2 channel sources. Users of smaller systems with satellite speakers will greatly benefit from this as true stereo content would require the use of a subwoofer to be fully appreciated.

Subwoofer Group Delay Adjustments
Receivers and processors with this feature adjust the digital delay of the subwoofer channel for proper integration with the speaker system, ensuring a more uniform blend.

Channel Trim Accuracy +/- 0.5dB step-sizes
The level of adjustment precision required for balancing each channel is about 0.5dB, rather than 1dB as found in many units. Please see our article on Human Hearing Amplitude Sensitivity for more information.

Channel Group Delay in 1ft (or less) Step-sizes
This feature adjusts the digital delay of the speaker channels for proper time alignment ensuring optimal frequency response and system integration. Higher resolution adjustments that are less than or equal to 1ft increments are important for getting precise control over delay.

Independent Channel Trims for 7.1 In
The ability to adjust channel levels for the EXT audio inputs independent of the global trim settings is an important feature that is useful for tweaking. This is especially true for DVD-A/SACD since the subwoofer levels are almost always different than with DD/DTS source material.

Independent Xover Setting for 2ch Bonus Feature
This is a useful feature for audiophiles looking to run their main speakers full range for 2-channel source material. It enables supplemental subwoofer reinforcement for the bottom-most octaves of the program material.

Sub Output 2ch Analog Bypass/Direct Bonus Feature
This signifies being able to use the subwoofer even for 2 channel sources when in a processor or receiver’s “Pure Direct” or “Analog Bypass” mode. It necessitates the need for a split of the main feed that allows DSP to only affect the subwoofer information while still passing a pure analogue stereo signal.

Opt. Main Bass Combined with Subwoofer Output Bonus Feature
In some cases, being able to have the main channels’ bass directed to both the ‘Large’ main channels and the subwoofer is helpful to provide more uniform bass distribution/system integration throughout the room. Be aware that use of this feature can also cause excessive bass boost in the transition region between the main speakers and subwoofer.

Independent Source Levels for All Inputs Bonus Feature
This feature signifies the ability to tweak source levels for each input. This can be useful for compensating for level differences between sources such as with a cable TV set top box and your DVD player. Setting uniform levels insures that you do not have to reach for the volume control each time you switch sources.

Independent Channel Trims for All Modes Bonus Feature
It is a beneficial feature to be able to tweak channel levels for all modes (i.e. Dolby Digital, DTS, Pro Logic II, etc). This is especially useful with program sources known to boost levels in the surround channels or if you desire to customize levels for different surround modes to your liking.

Optional Digital Bass Management for 7.1 Inputs Bonus Feature
This is a very useful feature when using a Universal DVD player lacking a high resolution digital interface (i.e. IEEE 1394) for transmission of DVD-A/SACD. It allows for the incoming signal to be run through an analogue to digital converter so that proper bass management and digital delay compensation can be made for these formats. We have found that with top-quality DACs, there is no audible loss of resolution or quality from the conversion.

Audio / Video Inputs & Outputs

> 2 Component Video In & >1 Out
While the advent of HDMI video switching may have saved the day for lack of multiple component inputs, we still look for at least three to deem a component as meeting the full criteria for this feature. With the advent of modern video game consoles and higher-resolution cable TV set-top boxes, we really feel all serious receivers and processor should have at least four (4) component inputs – even at the expense of losing a couple composite and s-video inputs along the way.

>3 Digital Toslink/Coax In & >1 Out
Another important feature is whether a device has enough S/PDIF inputs and at least one output. We recommend a minimum of 3 inputs of each for full credit.

>1 Subwoofer Output
We are avid supporters of multiple subwoofers as it greatly improves system integration and uniform bass distribution throughout the listening room. It is best, however if systems provide discrete subwoofer outputs – and even better if the outputs have independent level and distance compensation settings. To get full scoring, the sub outs must be truly independent and have their own settings.

5.1/7.1 Multi-channel Inputs
This feature is almost becoming standard for entry level receivers, however we feel it is important at this point to note on our checklist as it provides a way to appreciate DVD-Audio and SACD without the use of a high-resolution audio connection like IEEE 1394.

Balanced Analog I/Os Bonus Feature
While it is questionable as to whether this offers any real sonic benefit to a well-designed system, balanced outputs are a sought-after feature and we would be lax to not have an easy way of identifying whether a processor or receiver had them.

>2 DVI/HDMI Input & 1 Output Bonus Feature
Digital video inputs and outputs are the latest connection type to grace the back panels of mid-fi and hi-fi receivers and processors. These connections provide ease of use and switching for those with the newest products implementing DVI and HDMI and are coveted amongst home theater shoppers. We feel that 3 digital inputs and at least one output are the minimum requirements for obtaining full credit.

IEEE 1394 I/O or Equivalent Bonus Feature
IEEE-1394 is the new, fast external serial bus standard that supports data transfer rates of up to 400 Mbps (400 million bits per second). It is used primarily for multimedia devices such as camcorders, computers, video cassette recorders (VCR's), digital audio recording workstations and, in this case, a digital transport for high resolution audio (DVD-A,SACD, DD/DTS).