5
Features
1.
XLR Output 1:
Connect this ba4 dBu
XLR output to your mixer, effects processor,
recorder, etc.
2.
RCA Input 1:
Connect a CD player or
multimedia device to this unbalanced -10 dBV
input.
3.
XLR Output 2:
Connect this ba4 dBu
XLR output to your mixer, effects processor,
recorder, etc.
4.
RCA Input 2:
Connect a CD player or
multimedia device to this unbalanced -10 dBV
input.
Conversion Ratio
The casual observer would think that to convert -10 dBV to +4 dBu, you would need 14 dB of gain.
However, you actually 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 may feel you cannot use a transformer to convert between -10 dBV and +4 dBu
because of low impedances. However, 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 20 k
Ω
or greater (50k and 100 k
Ω
are not uncommon), this should never be difficult.
A 15 k
Ω
load winds up looking like 1 k
Ω
to the equipment 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. 3.16 volts
driving 1 k
Ω
only requires 3.16 milliamps, which is a very modest requirement for -10 dBV equipment
to deliver.
Wiring
The BB22 follows AES/ANSI/IEC standards of pin 2 positive and pin 3 negative. Note that the shields
(commons) of the RCA jacks are not tied together. This provides better ground isolation for
unbalanced units. A positive signal applied to the tip of the RCA jack causes a positive signal to
appear on pin 2 of the XLR, and vice-versa if signal direction is reversed.
Signal Direction
The signal can be converted through the channels in either direction. The only problem arises in the
gender of the XLR connector. The solution requires using XLR adapters or special cables.
OUTPUT 1
OUTPUT 2
+4dBu
+4dBu
-10dBV
-10dBV
INPUT 2
INPUT 1
1
2
1
2
3
4
