Sony G90 manual After DSP Digital to Analog Conversion, InterFacing the User

copy-protection problem), DVD-Audio and

SACD players will have six analog outputs for

reproducing multi-channel music discs. Unless

your controller has a discrete six-channel ana-

log input, you won’t be able to play high-reso-

lution multi-channel music through your sys-

tem until the copy-protection dust has settled.

The six-channel analog input approach has its

drawbacks: You’re paying for six DACs in the DVD-

A or SACD player and for six DACs in the controller. It

would obviously be better and more cost effective if multi-

channel DVD-A or SACD was provided to the controller in a

single digital data stream. Until then, the most important

thing to look for is that the analog bypass is available for the

DVD-A and SACD signals. Adding extra layers of conversion

will only degrade the sound. The issue becomes more com-

plicated when you add bass management to the mix, since

bass management is done in the digital domain.

After DSP – Digital to Analog

Conversion

Every 5.1-channel controller has six digital-to-analog con-

verters (DACs) and six analog output stages built into it. The

DACs convert the digital data for each channel into analog

signals. The quality of these DACs and the subsequent ana-

log output stage (which drives the power amplifier through

interconnects) is crucial to realizing good sound quality.

DACs vary greatly in their sound, and a poor-sounding DAC

(or a poor implementation of a good one) can ruin an other-

wise excellent controller. More expensive controllers use

higher quality parts and design techniques, including metal-

film resistors, polystyrene capacitors, four-layer circuit-

boards, and exotic circuit board material. Also look for ana-

log stages made from discrete transistors instead of inex-

pensive operational-amplifier chips. Some High End compa-

nies now have considerable expertise in designing cutting-

edge digital converters, expertise they can apply to building

multi-channel digital controllers.

Don’t be swayed by marketing hype that touts the DACs as

“24-bit.” Although the DAC may have 24 resistor “rungs” on its

“ladder,” that doesn’t mean it has 24-bit resolution. The last

four bits often contain just noise, not real information.

Because real-world DAC technology is limited to 20-bits, those

last four bits are known in the industry as “marketing bits.”

The best minds working today in digital conversion cite

the historical “two bits per decade” rule of con-

verter advancement. Assuming this rate contin-

ues, consider this: 24-bit digital audio has a the-

oretical noise floor of –144 dBV, but the thermal

noise produced by a single 1,000 ohm resistor

(generated by random movement of electrons)

at room temperature is –125 dBV, a noise floor

19 dB higher than a 24-bit converter’s theoretical

limit. I doubt that converter technology will

advance beyond 21 bits without a fundamental break-

through employing new DAC architectures.

(Inter)Facing the User

Most of this article has been concerned with the path of a sig-

nal from input to output and the wide variety of turns

between. But how the user operates a controller with all

these features is just as important as the raw technology that

makes the magic. A controller can be easy to set up initially

and a joy to use on a daily basis. Or it can be a confusing

nightmare that makes you feel lucky to get any sound at all

from your speakers – never mind fine-tuning the controller

for the best performance. Which of these scenarios comes to

pass is determined by the controller’s user interface, a term

that encompasses the front-panel controls and display, the

remote control, and the on-screen display. Some products are

easy and intuitive to use; others are frustrating and complex.

Before buying a controller, ask the salesman to run through

the system set-up; if he has a hard time, watch out. Second,

play with the unit yourself in the store; you’ll not only get a feel

for how it works, you can ask questions before you take the

controller home. Third, take a close look at the remote; if it is

covered by a sea of identically sized, shaped, and colored but-

tons, it doesn’t bode well for the rest of the user interface. The

buttons should be color coded, grouped by function, and fea-

ture different sizes according to their frequency of use or func-

tion. And it’s all to the better if they light up in the dark.

Do not underestimate the importance of a well-designed

user interface. It could make the difference between loving

and hating the component that is the heart and brain of your

multi-channel system.

For more information about controllers and other home

theater topics, check out Robert Harley’s book Home The-

ater for Everyone. For information, or to order a copy, call

800-848-5099. Website: www.hifibooks.com

Component-Video Switching

ne feature lacking on even some	trollers with component-video switching,
High End controllers is compo-	however, have no on-screen display from
Onent video input and output jacks.	the component-video output.
Component video, carried on three sepa-	If you have a single component-video
rate cables, offers vastly improved picture	source (a DVD player, for example) and a
quality over composite video, and is even	video monitor with component-video
better than S-Video. As more and more	input, you can simply run the component-
products with composite-video connec-	video cables directly from the DVD play-
tions become available (DVD players,	er to your video monitor, bypassing the
HDTV set-top boxes, video monitors),	controller’s video-switching function. This
component-video switching becomes an	technique requires that you switch inputs
increasingly important feature. Most con -	on your video monitor to watch a DVD.

Even if your controller has component- video switching, however, none available today offer cross-format conversion (i.e., S-Video input to component-video out- put), meaning you still must switch inputs on your video monitor when watching a component-video source. Although component-video switch- ing will

become increasingly common, multiple

RCA jacks take up valuable rear-panel real estate. Some products just don’t have

the room. RH