User manual RANE FBB 44 DATASHEET

[. . . ] Professional Audio Products FBB 44 BALANCE BUDDY FBB 44 Balance Buddy General Description The Rane FBB 44 Balance Buddy is a handy professional-grade tool used to convert and provide isolation for those annoying unbalanced -10dBV level RCA outputs up to balanced +4dBu professional 3-pin (XLR-type) inputs--and viceversa. Two channels each way, or a stereo pair each way (however you prefer to think about it). [. . . ] The first (dBV) references everything to 1. 0 volt, while the second (dBu) references everything to 0. 775 volts (this comes from the old power reference of 0dBm, which equaled 1mW into 600 ohms, which equaled . 775 volts). Driving Impedances Some people wrongly feel you cannot use a transformer to convert between -10dBV and +4dBu because of low impedances. This is not a problem as long as you use them to interconnect equipment with at least 15k ohms input impedance. Since most professional products have input impedances of 20k ohms or greater (50k and 100k ohms are not uncommom), this should never be difficult. A 15k ohm load winds up looking like 1k ohm to the equipment with the 10dBV output (due to transformer action). The maximum transformer output level of +24dBu occurs with an input level of +10dBV, which equals 3. 16 volts. Wiring The FBB 44 follows AES/ANSI/IEC standards of pin 2 positive and pin 3 negative. To insure complete isolation of all channels, pin 1 has no internal connection, but the case (shell) is connected to chassis ground. (See schematic diagram. ) Note the shields (commons) of the RCA jacks are tied for the Inputs and the Outputs but not to each other. Polarity A positive signal applied to pin 2 of the 3-pin connectors causes a positive signal to appear on the tip of the associated RCA jacks, and vice-versa. For situations where this does not agree with the equipment being interconnected, the INVERT switch reverses polarity. Mounting The FBB 44 is packaged in a standard Rane Flex chassis which is compatible with all HR products and accessories. [. . . ] W. , Mukilteo, WA 98275-5098 TEL(206) 355-6000 FAX(206) 347-7757 Printed in the U. S. A. on Recycled Paper All features & specifications subject to change without notice 520-267 SEP94 [. . . ]