Rane FBB 44 User Manual

Professional Audio Products

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 FBB 44 converts one pair from -10dBV to
+4dBu and another pair from +4dBu to -10dBV
simultaneously. There are two female and two
male XLR-type connectors, and four RCA jacks.

FBB 44

BALANCE BUDDY

Signal-to-noise performance is perfectly
preserved using the FBB 44, since it uses only
passive transformers to convert signal levels. It
adds no additional noise whatsoever. Use of
professional quality nickel core (“80” Ni)
transformers guarantee low distortion, wide
bandwidth and high signal handling capability.

The FBB 44’s isolation transformers provide
a quick and affordable answer to all jobs
requiring signal level conversion and output
balancing.

Features

• 2 CH’s: -10dBV TO +4dBu CONVERSION

• 2 CH’s: +4dBu TO -10dBV CONVERSION

• NICKEL CORE “80" Ni TRANSFORMERS

• WIDE BANDWIDTH

• LOW DISTORTION

• +24dBu MAX LEVELS

• RCA & 3-PIN (XLR-TYPE) JACKS

• FLEX HR CHASSIS

Parameter Specification Limit Units Conditions/Comments

Transformer Construction Nickel Core Bobbin Wound Grade “80” Ni
Turns Ratio 1:3.89 -10dBV (316mV): +4dBu (1.23V)
Maximum Levels (In or Out )

..........-10dBV +12.2 (40-20kHz); +6.7 (20Hz) 0.5dB dBu 1% THD Point

..........+4dBu +24 (40-20kHz); +18.5 (20Hz) 0.5dB dBu 1% THD Point

Input Impedance (Load Impedances As Shown)

..........-10dBV 1k 5 % Ohms Load Impedance 15k Ohms

..........+4dBu 15k 5 % Ohms Load Impedance 1k Ohms

Insertion Loss 0.5 0.1 dB With Recommended Load Impedance
DC Resistance 47.5/200 10% Ohms -10dBV/+4dBu
Frequency Response 20-20kHz 0.2 dB +4dBu In/Out
Bandwidth 90kHz -3 dB Half Power Frequency
THD + Noise less than .04 (40-20kHz) .01 % +4dBu In/Out
Shipping Weights 6 lb (2.8 kg)
All specifications apply both directions, unless noted. 0dBu=0.775 volts; 0dBV=1.0 volts

FBB 44

BALANCE BUDDY

Rear Panel Block Diagram

Application Information

Professional Audio Products

Conversion Ratio

The casual observer would think
to convert -10dBV to +4dBu you
would need 14dB of gain. The
casual observer would be wrong.
You only need 12dB of gain. The
reason is not only do you change
levels, you also change reference
levels—from dBV to dBu. 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 imped-
ance. 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). This may seem
excessively low, but is not in practice. The maximum trans­former output level of +24dBu occurs with an input level of
+10dBV, which equals 3.16 volts. And 3.16 volts driving 1k
ohms only requires 3.16 milliamps. A very modest require­ment for any -10dBV equipment to deliver.

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. This
allows ground isolation of stereo Input and Output pairs.

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.
When used with other Flex products, the FBB 44 may be
mounted in the FVR 10 Vertical Rack. Alternatively, choose
one of the horizontal mounting kits to mount one or two units
side-by-side into a standard 19" rack.

Chassis Grounding

A tapped hole and a 6-32 screw is provided for chassis
grounding purposes. Good practice dictates earth-grounding
the FBB 44. If the grounding integrity of the rack screws is in
doubt, then run a wire from this screw to a known good
ground.

©Rane Corporation 10802 47th Ave. W., Mukilteo, WA 98275-5098 TEL[phone] FAX[phone]

Printed in the U.S.A. on Recycled Paper

All features & specifications subject to change without notice 520-267 SEP94