Proceed PAV audio/video preamplifier Page 2

I don't have enough space here to discuss all the operational functions and features of the PAV, but there's one quite useful feature that's "buried" on p.47 of the manual under "Using the PAV/The Operate Menu/volume display." The volume can be displayed on an absolute scale ranging from 0 to 112, or on a relative scale, with a level of 0 indicating the calibration reference level—the level at which most soundtracks are mixed. (With proper calibration, this level, in THX mode, is also the level often referred to as "THX reference" level.) I preferred the relative scale.

The Proceed PAV is designed around the Analog Devices SSM2125A PMI Pro Logic chip. With the exception of the surround delay, the internal processing is all analog. All audio and video inputs are buffered. High-quality parts are used throughout, some of them also appearing in the Mark Levinson No.38 preamplifier. Each section—audio, video, and control—has its own isolated power supply driven from separate secondary windings on the toroidal power transformer. The input switching, surround decoding, rear-channel delay, and volume and input driver circuits are all independently regulated: in all, 17 regulation stages.

The PAV's decorrelation circuitry is rather unusual. Proceed claims to be the first manufacturer to perform decorrelation by subtly shifting the left and right surrounds randomly in time. Other manufacturers use a frequency or a phase shift, neither of which, argues Madrigal, sounds as natural. In fact, Madrigal is so convinced of this that they've used some 250 components to implement this time-based decorrelation (compared with the approximately 50 components in the basic Pro Logic circuitry).

To improve RF performance, a four-layer circuit board is used for the control, video, and digital circuits. The video circuitry has a 20MHz bandwidth, input to output, with a 65MHz (at 75 ohms) bandwidth line-driver on each output. The video on-screen character generator is in-circuit only while characters are actually displayed, so it won't degrade video performance in normal operation.

Most of the PAV's major operating functions are controlled by a replaceable ROM chip; for upgrades, the manufacturer simply burns and distributes a new one. A recent change—which I haven't yet incorporated as I write this review—includes a phantom center option, the lack of which was a conspicuous omission in the original design. The same change also offers the choice of blue or black screens when an inactive video input is selected, which is useful if you wish to listen to music in the dark.

I did encounter a problem with an early sample of the PAV: On two occasions the on-screen menus refused to appear when commanded. A new remote control didn't alleviate the problem—it cured itself each time after a few days, for no apparent reason. This sample was from the prototype run; a later production sample exhibited no such anomaly.

Film sound
Pro Logic involves a considerable amount of processing to "fold" the original four-channel master into the two channels on the laserdisc or other recorded medium, and again to recover some semblance of four channels on playback. Yet I find myself consistently amazed at how effective the result can be when it's a part of an overall home audio/video experience. While still noticeably short of hi-fi, audio-only reproduction in a top-quality Home Theater system with the best sources can nevertheless be totally absorbing, and far superior to any optical Dolby Stereo soundtrack I've ever heard in any theater.

I find it hard to imagine any better realization of the Pro Logic concept than that in the Proceed PAV. It's smooth yet detailed, free of distracting artifacts, and quiet. In the world of high-end audio-only playback, these would be assumed minimum standards. In the world of Pro Logic Home Theater, they're important virtues.

I did most of my video-sound listening to the PAV in its THX mode. When I first heard a home THX system a couple of years ago, I confess that I found the sound rather dull—lacking in spaciousness on top and somewhat overripe lower down. With the PAV in my room, driving any of the speaker combinations mentioned above, this was very definitely not the case. With the THX circuits engaged, the top end sounded almost sweet on the best soundtracks (particularly with the McIntosh front-channel loudspeakers), though appropriately gutsy and in-your-face when needed. Switching to straight Pro Logic did increase the sparkle and openness in the treble, but at the cost, on many films, of a less than sweet and silky sound. The blame for this appears to be in the recordings, not the PAV; this substantiates, for me at least, the validity of THX re-equalization for soundtracks.