12
THEORY OF OPERATION
1.2 Gain Specifications
1.2.1 Purpose and Philosophy
The purpose of this specification is to define all relevant gain levels in the Bose
®
Personalized
Amplification System™ Power Stand and to specify procedures, for how these gains can be
measured.
We’ll do this primarily by specifying a “nominal” level at each point. The “nominal” level repre-
sents the desired operating point. This is the level where we anticipate that the bulk of operation
occurs. Wherever warranted we will also do a headroom analysis in order to specify or derive
the maximum acceptable level before a stage clips or overloads.
The gain structure is designed in a way so that there is one point that handles the main system
constraint. This point is the digital limiter inside the DSP. If all levels are “nominal” the system
should just reach full output, the digital limiter should just be starting to work and all other
analog signals (except for the power amp, off course) should still have reasonable amounts of
headroom. This design allows controlling the high-signal behavior of the system completely in
software through the digital limiter and still offers good signal-to-noise properties.
1.2.2 Gains and Signal Levels
First, we need to define some reference levels for all the adjustable controls in the system. For
the “nominal” signal levels, we assume certain settings in those controls, and define the gain of
each adjustable section.
Table 1. Adjustable Controls: Gain range and nominal settings
Next we define all the nominal signal levels for full power output. All signal levels are specified in
dBV unbalanced unless otherwise noted. All levels in front of the DSP can be measured as such
directly. The post-DSP peak output levels can only be observed when the limiter is switched off.
Control Gain
Range
Nominal
Comment
TRIM –
Microphone
PreAmp
+8dB to +50dB
(XLR Balanced Input)
+21dB @
Pot center
Center vs. Max/Min dependent on
Pot taper.
TRIM –Line
PreAmp
-12dB to +30dB (1/4”
Unbalanced Input)
+1dB @
Pot center
Center vs. Max/Min dependent on
available Pot tapers.
Ch1, Ch2
Volume
(Remote)
-40dB to 0dB
-10 dB @
Pot center
Adjustment range is restricted and
log taper is implemented by a look-
up table, in order to make this a
usable control.
Master
Volume
(Remote)
-80dB to +22dB
+10 dB @
Pot center
Adjustment range is defined and log
taper is implemented by a look-up
table, in order to make this a usable
control.
Summary of Contents for Personalized Amplification System
Page 3: ...3 THEORY OF OPERATION Figure 1 PS1 signal flow Diagram ...
Page 44: ...44 APPENDIX CS5361 AD Converter Pinout and Table ...
Page 45: ...45 APPENDIX CS8406 Digital Audio Interface Transmitter ...
Page 46: ...46 APPENDIX CS8416 Digital Audio Interface Receiver ...
Page 47: ...47 APPENDIX TDA8929T Digital Amplifier Controller ...
Page 48: ...48 APPENDIX TDA8927J Digital Power Amplifier ...
