AV Preamplifier and 7.1 Surround Sound Processor Reviews

The modern AV preamp is a jack-of-all-trades. While at its core it is a switching device for audio and video sources, the modern AV preamp has to do much more than switch between inputs. First, it must offer all the inputs currently available to allow itself to integrate into any system. This means older connectors and formats such as composite, S-Video and component video need to be supported for many users, as well as HDMI. Video scaling and transcoding are also key for ease of use, allowing a user to connect their display with a single cable, presumably HDMI. The modern AV preamp must also provide exceptional two-channel and multi-channel audio performance. While audiophiles may form a hybrid system, where a dedicated two-channel preamplifier covers the stereo sources and a zero gain or home theater bypass allows use of the home theater for multi-channel use, most do not want to deal with the added headaches and space required for such a system. Most users want a single box to satisfy both their home theater and two-channel listening needs.

Everything You Need To Know About Home Theater AV Preamps

1.0 Background

1.1 What is an AV Preamp?
1.2 Brief History of the AV Preamp

2.0 What Does an AV Preamp Do?

2.1 The Role of HDMI in today's AV preamp
2.2 Surround Sound Modes in AV preamps
2.3 Room Correction and EQ in AV preamps

3.0 Notable AV Preamps

1.0 Backround

1.1 What is an AV Preamp?
An AV preamp is an audio/video component that has many functions in a modern home theater system, including switching audio and video inputs, adding or processing surround sound to the audio signal path, processing or scaling video signals from sources and beyond. Unlike a traditional "receiver," an AV preamp does not have internal amplifiers. AV preamps are plugged into power amplifiers that often drive between five (5.1) and seven (7.1) speakers. They also output signal for the LFE or subwoofer channel of surround systems, which is also known as the .1, made famous in the term 5.1 or 7.1 surround.

1.2 Brief History of The AV Preamp
Born from AV and even stereo receivers, AV preamps have almost always been step-up, higher-end solutions for the needs of audiophiles and movie enthusiasts who want to create the movie or surround sound experience in their home theater or multi-channel audio systems. AV preamps or surround sound processors (SSPs) have always been used in the professional cinema world, as the need to fill large physical spaces required cienplexes to use large speakers and beefy power amplifiers.

Today, audiophiles and videophiles alike use AV preamps to achieve top of the line surround sound reproduction for sources like DVD-Audio, SACD, HD DVD, traditional DVD-Video and Blu-ray. With Blu-ray (as well as the now dead HD DVD format), AV preamps usually come packed with HDMI inputs, so that the master quality sound and 1080p video can be sent into the preamp via one copy-protected cable. Chipsets have been slow to get to market, keeping receivers and AV preamps alike somewhat behind the technological curve when it comes to AV source-switching, in contrast to the HDMI connectivity of the latest sources like Blu-ray players, as well as the latest 1080p HDTV sets.

2.0 What Does an AV Preamp Do?
• AV preamps boost the line level audio signal from analog and digital sources to levels that a power amplifier can detect and boost again to successfully power a loudspeaker.
• AV preamps accept multi-channel analog audio inputs from sources like SACD players, DVD-Audio players, HD DVD players, D-VHS decks and PCM audio from Blu-ray players.
• AV preamps process audio signals that are mono, stereo or multi-channel into a variety of surround sound modes. The user can often select these modes or can use the default mode on the preamp. AV preamps often have matrix modes that can make a stereo signal into a faux surround sound format. Yamaha was famous for these modes in their receivers in the 1980s. Advanced processing has made the matrix modes on many AV preamps to sound quite convincing. However, it is always best to have source material mastered for surround by a mixing engineer on the disc itself.
• AV preamps accept many varieties of video inputs via HDMI, DVI, component video, S-Video and often composite video sources.
• Some AV preamps come with video processing that allows the user to up-convert video sources from traditional standard-definition 480i video to higher resolutions that match the resolution of their HDTV sets such as 720p, 1080i or 1080p video. Note: up-converted video never looks as good as the native HDTV signal, even when using the highest-performance video processing, which is only found in the most expensive AV preamps. More commonly, video processing is done outside of the AV preamp, but with the rise in popularity of HDMI for both HD audio and video sources (specifically Blu-ray), more and more AV preamps are adding HD-quality video processing.
• Some AV preamps have tuners built in that can receive AM, FM, XM, Sirius or, most rarely, Internet radio.
• AV preamps are often controlled by RS-232 connectivity, which is a hard-wired control system used in the highest-end remote systems, such as Crestron, Control 4 and AMX. Other AV preamps work with RF and or IR remote control systems.
• AV preamps often come with programmable and backlit "learning" remote controls that can be used to run entire systems.
• Many AV preamps have SD or even HD video displays on the front of the component, which allow programming, source control and even previewing source material right on the front of the unit.

2.1 The Role of HDMI in Today's AV Preamp
The HDMI input is the biggest addition to AV preamps since the advent of Dolby Pro Logic surround sound in the early 1980s. HDMI is an encrypted way to send HD-quality audio and 1080p HD video via one cable from a modern source like a Blu-ray player (it's also used widely with cable boxes, HD DVD players, HD DVRs and HD game machines at varying other levels of HD resolutions, both with copy protection and without) to an AV preamp. AV installers and custom AV integrators report enthusiastically that all has not been perfect in the world of HDMI, which on the surface seems like a one-cable, copy-protected solution. Many early HDMI systems that used HDMI solely for video were so unreliable that installers would only use component video (an analog cable capable of passing up to 1080i resolutions) for their systems. Some consumers rebelled against HDMI because of the idea of computer companies forcing copy protection into their systems. However, Hollywood wasn't going to release HD content without some level of copy protection. In the case of HDMI, the copy protection is called HDCP and, like all copy protection schemes, it has been broken. Most consumers don't care, but Hollywood does, because of rampant overseas bootlegging.

HDMI to date has gone through numerous updates, leaving mainstream and audiophile manufacturers scratching their heads. Compatibility issues with different versions of HDMI are rampant and OEM manufacturers (the companies hired to actually make AV preamps for many audiophile and mainstream companies) struggle to keep up with the connectivity changes.

Handshake issues also plagued many AV preamps, as copy-protected HD sources didn't always like being connected through an AV preamp, even if the preamp only switched video. Often, an HDMI 1.3a source like a Blu-ray player wouldn't effectively connect via an AV preamp equipped with an earlier HDMI version, causing a handshake issue and passing no video. More frustratingly, HDMI handshake issues can be intermittent, causing systems to work effectively sometimes and fail to pass signal at other times.

HDMI connectors are made of plastic and do not lock in place. They break easily (albeit not as easily as S-video connectors) and can fall out of their inputs, causing system problems.

HDMI and other soft and firmware updates have been added to AV preamps, either via Ethernet connections to the Internet and or via computer updates, mostly from PCs. This has allowed many AV preamps to stay current with the laundry list of features consumers demand, as well as to keep up with the connectivity updates that come from HDMI chip-makers.

2.2 Surround Sound in AV Preamps
While most AV preamps can very effectively pass a stereo signal, most clients use them to receive surround sound material and/or convert stereo signals into faux surround sound.

Native surround sound can come from sources like DVD-Audio and SACD via a 5.1 (six analog) inputs or via digital audio inputs, say, from a DVD-Video player playing a movie using lossy surround sound formats like Dolby Digital or DTS. Native 5.1 and 7.1 surround sound can also come on an HDMI cable, along with HD video. The latest HDMI AV preamps can take this pure bit-stream HD audio information and process it into Dolby True HD or DTS HD Master Audio. This is the state of the art of surround sound at this point.

Matrix or faux surround sound modes were made popular by Yamaha in their 1980s receivers. They added delay and redirected sound to affect speakers in relatively crude ways, creating effects like "church" or "stadium," which most purists avoided. Today's matrix surround sound formats are very good, thanks to the improved software and internal processing power in AV preamps. High-end companies like Meridian have modes such as "tri-field" that can effectively expand a stereo source from a compact disc to widen the sound field to use most of the front speakers. Even audiophiles today find these matrix modes to be dramatically improved.

2.3 EQ and Room Correction in AV Preamps
One of the newest trends in AV preamps is the addition of room correction. As AV preamps have adopted more and more computing power, it is now possible for them to equalize your system to deal with acoustical anomalies in the room. Set-ups range from amazingly simple to very complex, with many needing professional calibration by an installer or acoustician.

Audyssey is at the forefront of room correction for home theater preamps. Meridian, Harman, Integra and many others offer room correction for their latest AV preamps. Many come equipped with a mic and an auto set-up that most savvy consumers can use with desirable results. Neptune Audio makes an outboard EQ and room correction model for higher-end home theater system. Wisdom Audio uses Audyssey EQs in their electronics for their ultimate-grade on-wall and in-wall speakers.

3.0 Notable AV Preamps
• Lexicon: Lexicon, owned by Harman International, is a reference-standard brand for professional AV preamps, has also made and sold some of the more important AV preamps in the history of home theater. These preamps include the Lexicon CP2, which was used to add Dolby Pro Logic to existing audiophile systems in the late 1980s and early 1990s. Another notable AV preamp from Lexicon is the MC12 HD, which is a state of the art HDMI switching audiophile preamp costing nearly $20,000.
• Fosgate: Fosgate is a brand of electronics that was well known in the world of pro audio and even car audio. They made groundbreaking preamps and surround sound processors in the Dolby Pro Logic era. The company is no longer in business today.
• Millennium: This $399 black box solution was the first consumer-grade processor to process DTS surround sound for existing AV preamps and receivers. The company is no longer in business, as most AV preamps and receivers now have these features built into them.
• Theta Casablanca: The audiophile-grade Theta Casablanca was the first high-performance AV preamp to come from a highly respected audiophile company. While riddled with early reliability problems, the Casablanca has been upgraded and stabilized to the point where it is still sold today. Theta was recently sold by its founder to ATI, which makes power amplifiers in the Los Angeles area.
• Meridian 861: The Meridian 861 is considered by many to be the best-sounding AV preamp ever built. It is also one of the most expensive AV preamps ever sold, with card configurations that can take the retail price to over $20,000. The 861 is arguably the most upgradeable AV component in high-end audio/video history, as you can upgrade an 861 from its 1994 version 1 to a current version 4 Meridian 861.
Mark Levinson No. 502: Harman's premium line just released this $35,000 AV preamp, which is designed to process and handle all of the latest features, while keeping the audiophile signal pure.