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Dec 1, 1999 12:00 PM, Gino Robair

           
 

EGO SYSTEMS Dr. D The Dr. D universal signal converter ($120), from Ego Systems, routes S/PDIF signals between digital devices with different types of connectors: optical (Toslink), coaxial (RCA), and XLR. The term universal signal converter is misleading because the Dr. D is merely an S/PDIF interface converter that changes the impedance and voltage of the signal so that it will pass through the different connector types, including XLR. The Dr. D does not change the channel status bits that differentiate AES/EBU from S/PDIF-which is what the term universal signal converter leads one to believe.

The Little Things That Count The S/PDIF (a consumer format known officially as IEC 958 Type II) and AES/EBU formats differ in peak-to-peak voltage (0.5 to 1 volt and 2 to 7 volts, respectively) as well as cable impedance (75 ohms and 110 ohms, respectively). The formats are otherwise very similar, so most machines require only a change in voltage and impedance and can overlook the difference in subcode information.

However, certain digital recorders-typically older models-are in fact very particular about the information in the subcode. Little did I know that the two DAT machines I own, both of which are Panasonic SV-3700s, were among those picky machines. Apparently, the SV-3700 is not "reasonably flexible and tolerant of slight foos in the signal," as the Dr. D manual so quaintly puts it; consequently, some routings didn't work. The main reason is that the SV-3700 must receive a complete AES/EBU signal over the digital XLR jack and a complete S/PDIF signal over the coaxial jack.

On the other hand, the Dr. D worked well with a number of newer recorders by Fostex, Panasonic, Sony, and Tascam, as well as with the Apogee PSX-100 digital converter; the signals passed from one connector type to the other with no problems. In some cases, I had to set the AES/EBU XLR connector of the receiving unit to receive an S/PDIF signal, a procedure that is not possible with an SV-3700.

In addition to its low price, the Dr. D has a small footprint (it's a little smaller than the average stompbox), is well built, and is easy to set up and use. The idea is that you simply leave your digital devices plugged into the Dr. D and use its selector button to determine how it will route the signals.

Jacks on the Box For each type of jack (XLR, coaxial, and optical) you get an input and an output. The XLR jacks are on the unit's sides, whereas the other jacks reside on the rear panel. The front panel has a selector button that lets you cycle between the seven routing possibilities.

Three of the four lights on the front panel, one devoted to each connector type, indicate routing status. The fourth light is the power indicator. The Dr. D has no power switch; the moment you plug in the wall-wart connector, the unit is on.

The Dr. D is flexible. Take, for example, these three typical routings: optical input to optical, coaxial, and XLR output; optical to and from XLR, and from coaxial to coaxial; and optical to optical, coaxial to coaxial, and XLR to XLR. Each input and output can accommodate a different device, meaning you can send up to three separate simultaneous signals-from three players-to three recorders.

Nice Device In my own studio, I found the device handy for connecting my CD player (using the Dr. D's optical input) to a DAT machine (using the XLR digital output), the Apogee PSX-100 converter (using the optical output), and a sound card (using the coaxial output). Again, the CD player's IEC 958 Type II signal can go to any or all of the outputs simultaneously. I also have the option of hooking up another two digital devices to the remaining open inputs, in this case coaxial and XLR. The Dr. D has a lot of potential.

Overall EM Rating (1 through 5): 3

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