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BB 44X
BALANCE BUDDY
Block Diagram
T4
9
2
INPUT 1
OUTPUT 1
3 2
+4 dBu
-10 dBV
1
11
4
T3
9
2
INPUT 2
OUTPUT 2
2
3
+4 dBu
-10 dBV
1
11
4
Rear Panel
1 2
+4 dBu
INPUTS
BALANCED WIRING:
PIN 2 = POSITIVE
PIN 3 = NEGATIVE
BALANCED
PIN 1 = CHASSIS GROUND
Application Information
Conversion Ratio
The casual observer would think to convert -10 dBV to +4 dBu,
you would need 14 dB of gain. The casual observer would be
wrong. You only need 12 dB 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 0 dBm, which equaled 1mW into
600 Ω, which equaled .775 volts).
Driving Impedances
Some people wrongly feel you cannot use a transformer to
convert between -10 dBV and +4 dBu because of low imped-
ances. This is not a problem as long as you use them to intercon-
nect equipment with at least 15 kΩ input impedance. Since most
professional products have input impedances of 20 kΩ or greater
(50k and 100 kΩ are not uncommon), this should never be dif-
ficult. A 15 kΩ load winds up looking like 1 kΩ to the equip-
ment with the -10 dBV output (due to transformer action). This
may seem excessively low, but is not in practice. The maximum
transformer output level of +24 dBu occurs with an input level of
+10 dBV, which equals 3.16 volts. And 3.16 volts driving 1 kΩ
only requires 3.16 milliamps, which is a very modest requirement
for any -10 dBV equipment to deliver.
Wiring
The BB 44X follows AES/ANSI/IEC standards of pin 2 positive
and pin 3 negative. Note the shields (commons) of the RCA jacks
©Rane Corporation 10802 47th Ave. W., Mukilteo WA 98275-5098 TEL 425-355-6000 FAX 425-347-7757 WEB www.rane.com
Data Sheet-2
T2
2
9
INPUT 3
-10 dBV
+4 dBu
4
11
T1
2
9
INPUT 4
-10 dBV
+4 dBu
4
11
1
3
3 4
-10 dBV
-10 dBV
+4 dBu
OUT
IN
OUTPUTS
2
4
UNBALANCED
BALANCED
OUTPUT 3
2
3
1
OUTPUT 4
OPTION 88 Accessory
2
3
1
OPTION 88
5 6
BB 44X
MADE IN U.S.A.
RANE CORP.
+4 dBu
INPUTS
ACN 001 345 482
BALANCED
are tied for the Inputs and the Outputs but not to each other.
This allows ground isolation of stereo Input and Output pairs. A
positive signal applied to pin 2 of the XLR connectors causes a
positive signal to appear on the tip of the associated RCA jacks,
and vice-versa.
Signal Direction
Signal can be converted through the channels either direc-
tion. That means there is the possibility of having four channels
-10 dBV unbalanced to +4 dBu balanced, or vice versa (in the
standard unit). The only problem arises in the gender of the
XLR connector. The solution requires same-sex XLR adaptors or
special cables.
Chassis Grounding
A tapped hole and a #6-32 screw is provided for chassis ground-
ing purposes. Good practice dictates earth-grounding the
BB 44X. If the grounding integrity of the rack screws is in doubt,
run a wire from this screw to a known earth ground.
OPTION 88
The OPT 88 (Option-88) expands the BB 44X into an eight
channel model. The OPT 88 consists of a printed circuit board
with four additional transformers and jacks soldered in place. The
OPT 88 installs easily in the blank side of the BB 44X. Assembly
is simple: remove the cover, install the board in place, and secure
with the supplied mounting screws. No soldering required; all
you need are #1 and #2 Phillips screwdrivers.
All features & specifications subject to change without notice DOC 102926
5
7
7 8
-10 dBV
-10 dBV
+4 dBu
OUT
IN
OUTPUTS
6
8
UNBALANCED
BALANCED
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