Power Driver Integrated Full Digital Audio Amplifier
NTP-8230
8. MIXER
Channel mixer can be used in lots of application needs like pseudo stereo and etc. User can mix input
channels into each output channels with designated gains and polarity. Step size of mixer gain is
variable according to the gain level as shown below.
Volume Range (dB)
+18 ~ +6
Step (dB)
1
0.5
1
+5.5 ~ -5.5
-6 ~ -32
≤ 32
-∞
Table 3. Variable step mixing gain
In total, 6 mixing gain coefficients denoted as M[0x03], M[0x04], M[0x05], … M[0x08] are defined as
shown in the equation below. Each Mxx stores volume value in dB scale, and the number values
versus gain in dB are shown in the Appendix C. There are some places in the mixing matrix that are
considered as trivial connections and thus predefined as -∞ dB.
[Output Channels] = [Mixer Matrix] x [Input Channels]
CH1 OUT
CH2 OUT
CH3 OUT
M[0x03] M[0x04]
M[0x05] M[0x06]
M[0x07] M[0x08]
CH1 IN
CH2 IN
.
=
Figure 12. Mixer Matrix
In order to load mixer coefficients into internal memory, send the index value in the gain value table to
the register address 0x03~ 0x08.
Copyright ⓒ NeoFidelity, Inc.
Page 17
Document Number: DS8230 draft ver. 0.1
2011-01-11