Gain Structure For Line Input Sources; Testing The Audio Inputs And Outputs - Polycom Vortex EF2241 Application Note

G S
AIN TRUCTURE FOR
Once the external devices have been wired to the Vortex Device, the Input and/or Output gain of the Vortex
Device needs to be set to match the nominal level of the external devices. Here is a table that references
the types of connectors to the proper input / output level of a Vortex Device:
Table 2. Recommended input and output gain settings based on connection type
Connector Type
RCA
1/8 inch
XLR
Phoenix / Terminal Block
The issue of nominal levels will affect the gain structure of the Vortex Device. Devices that have RCA and
1/8 inch style connectors are normally designed to operate with a nominal level of .3 Vrms. The Vortex
Device is designed to operate with a nominal input and output level of .775 Vrms. This equates to a
difference of 8.24 dB between the two nominal levels. For simplicity, you may round that value to 10 dB.
Therefore, the inputs of the Vortex that receive consumer level outputs need to be set to +10 dB in order to
achieve a unity gain. The outputs of the Vortex will be about 10 dB too high for the consumer level
equipment and, in turn, need to be set to -10 dB to avoid clipping and to maintain enough headroom in the
consumer level devices.
The Input gain of a Vortex device that is connected to a SoundStation VTX 1000 should be set to +10 dB.
The Output gain of a Vortex device that is connected to a SoundStation VTX 1000 should be set to -10 dB.
The Input and Output gains of a Vortex Device that is connected to a VSX 8000 and any other balanced
devices should be set to 0 dB.
T A
ESTING THE
1. Go to S
, D
YSTEM
level should be around 0 dB on the B
listen to your own audio in the local room. That feature is under S
N E L .
EAR ND OOP
2. Go to System Info, Diagnostics, Audio, Speaker Test to listen to a codec-generated 400 Hz tone.
L I S
INE NPUT OURCES
Input Gain
+10 dB
+10 dB
0 dB
0 dB
I
UDIO NPUTS AND
, A , A
IAGNOSTICS UDIO UDIO
ALANCED
Output Gain
-10 dB
-10 dB
0 dB
0 dB
O
UTPUTS
M and then speak into one of the microphones. Your
ETER
I meter. You may also use the loop-back feature to
N
, D , N
YSTEM IAGNOSTICS ETWORK
,
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