Lab.gruppen PLM series Operation Manual page 89

As can be seen to the left, the improvement in noise performance (at the cost of losing headroom and
compression features) is only 0.6 dB. It is therefore recommended not to try to optimize performance in this
manner.
When using analog inputs:
Figure 12.4a illustrate how to minimize absolute noise within the PLM, while limiting available SPL.
Parameter list:
Input clip: 12 dBu
Amp gain: 22 dB
SNR: 105.5 dB
Absolute Noise Floor = -71.5 dBu
SPL is limited to -8.9 dB relative to clip in this "minimum absolute noise level application".
Figure 12.4b illustrate how to minimize absolute noise while achieving full power. In this illustration it can be
seen that there is no available headroom.
Parameter list:
Input clip: 12 dBu
Amp gain: 30.9 dB
SNR: 111.3 dB
Absolute Noise Floor = -68.4 dBu
60,0
40,0
20,0
0,0
-20,0
-40,0
-60,0
-80,0
-100,0
-120,0
-140,0
Analog AES Input
80,0
60,0
40,0
20,0
0,0
-20,0
-40,0
-60,0
-80,0
-100,0
-120,0
-140,0
Analog AES Input
Gain Structure: "Low SPL - Low Input" Application (Low noise with limited output)
Input Mixer Module In Module Out
Figure 12.4a: Minimizing noise
Gain Structure: "Low SPL - Low Input" Application (Low noise with limited output)
Input Mixer Module In Module Out Amp
Figure 12.4b: Minimizing noise
Amp Attenuation Analog Ref Amp Gain
Attenuation Analog Ref Amp Gain
PLM Series Operation Manual rev 1.1.3
12. Application Guide
Clip
Nominal
Noise
ISVPL Output
Clip
Nominal
Noise
ISVPL Output
89