The digital revolution did not eliminate the need for analog patch bays, nor did it simplify wiring or routing. No matter how modest your rig, a few different flavors of digital and analog interconnects will be required, plus a few flava-morphing boxes to allow all devices to communicate. The Hosa PBP-362 is a modular optical patch bay designed to emulate its analog counterpart- not a digitally controlled router but rows of inputs and outputs for manual patching. The PBP-362 can handle 8- channel ADAT Litepipe as well as stereo S/PDIF signals.
Four modules, each with three vertical rows, fit into a 1U 19" rack panel. The unit I tested had three identical MFO-363 patch modules (representing nine channels) plus one MSP-364 Litepipe Splitter Module (for creating two outputs from one source). A single wall wart powers all of the modules; distribution is daisy-chained in the rear. The circuit boards are protected on three sides, the bottom is open to access an "options" jumper for setting the relationship between top and bottom rows-half- normalled, full-normalled or "fixed" for thru-put only. With the exception of the splitter module, optical connections appear on both front and rear panels.
In the beginning, not all TOSLINK-equipped products could assure data exchange if cable length exceeded the 10- meter (32.8 feet) limit. I learned this the hard way when dabbling in the custom optical cable business. For example, in one instance, two boxes happily chatted at 44.1 kHz across a 50-foot cable, but suffered communication breakdown at 48 kHz. Using an extra long cable for the tests that follow will reveal potential vulnerability, if any. Staying within spec guarantees data headroom.
The first test was to establish a reference. A consumer CD player provided the source, routed through a Z-Systems Detangler to a Panasonic SV- 3800 DAT recorder, the latter connection fed by the 50-foot optical cable. To determine signal condition, the incoming signal at the DAT deck was monitored via oscilloscope. Zoomed in, the data is a bunch of toggling square waves that create what is referred to as an "eye pattern." (A Google search for this term yields pictures and an exhibition.) The transitions (from low to high and high to low) are more important than the "squareness," but the latter is a good indication of how well the data survived transit. So far, so good.
The Detangler was eliminated to see if it was "helping" the CD player. It wasn't. Then the PBP-362 was inserted to see its effect on the signal, which seemed the same if not slightly improved. While the signal being transmitted is digital, the journey from optical transmitter (TX) through cable to receiver (RX) is essentially analog so there is potential for signal degradation if connectors or cable are damaged, dirty or out of spec. The circuitry on either side of the TX and RX is level-tolerant (within reason), see for yourself by gradually withdrawing the connector while receiving or transmitting data.
S/PDIF is easy for the PBP-362; ADAT Litepipe has heavier traffic flow. Test two began with a Fostex R-8 as source (essentially a blackface Alesis ADAT with Fostex front panel and built-in sync) followed by the 50-foot optical cable to an Alesis AI-3 8-channel I/O box as reference. The Hosa PBP-362 was then inserted, with before and after scope measurements to confirm signal integrity.
Everything was still go, so I then did the unthinkable: looping through each channel of the PBP- 362 until the signal stopped-certainly not Hosa's intended application. Four channels good, five channels and the signal degraded to the equivalent of poor FM radio reception with much fuzz and static. Had each channel been a digital device-like an EQ or dynamics processor-the signal would have been re- clocked and rejuvenated. Instead, the collective noise of each optical device began to blur the signal, making data progressively harder to read. This is normal, kinda like using a lot of sustain on the guitar-great until you stop playing, then prepare for a wave of hiss that does not translate into data.
In summary, the Hosa PBP-362 is an easy-to-use, essential tool for those with optical toys in their digital arsenal. It augments what I already have-more optical devices than my current router can handle. At first, I did not care for the lack of bottom covers. It's not an issue while the PBP-362 is in the rack. But as anyone building a recording facility should know, there are times when any piece of gear can become vulnerable during the process-from sheet-rock dust to bits of solder and cut wires, so keep the PBP in the box until ready for use. (PBP-362 with one MFO-363 module $325 MSRP; MFO-363 expander module $250; MSP-364 Litepipe splitter module $65.00; www.hosatech.com)
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