SLASEG6B May 2018 – June 2020 TAS3251
The BQ coefficients format is as follows: The first BQ has B0 = 5.x, B1 = 6.x, B2 = 5.x, A1 = 2.x, and A2 = 1.x. The rest of the BQ have this format: B0 = 1.x, B1 = 2.x, B2 = 1.x, A1 = 2.x, and A2 = 1.x. This formatting maintains the highest possible resolution and noise performance. The 1.31 format restricts the ability to do high gains within the BQs and as a result requires gain compensation for the restriction. When generating BQ coefficients, ensure none of the BQ coefficients is greater than 1 by implementing gain compensation. The Gain compensation reduces the BQ coefficients gain to ensure all BQ coefficients are less than 1. The reduced gain is then reapplied in the subsequent gain scale block.
Gain compensation takes the maximum value of B0_DSP, B1_DSP, and B2_DSP after the BQ normalization shown in Table 27 is implemented. All the B coefficients are divided by maximum B coefficient value then multiplied by 0.999999999534339 (the nearest two’s complement 32-bit number to 1). The following calculations are done for each BQ in the PEQ block:
The calculations above insure all DSP BQ coefficients are in a 1.31 format. The reduced gains in the BQ 1.31 format is compensation for in the gain scale block. The following calculation is done for each channel.
The calculated k_BQ compensation value is then applied to the BQ gain scale in an 8.24 format. The BQ gain scale can also be used for volume control before the DRCs. The block can be considered as BQ gain scale and volume gain block. When the BQ gain scale block is used for volume control the coefficient value must be calculated as follows:
The BQ gain scale coefficients are located in book 0x8C, page 0x21 register 0x4C for left and register 0x50 for right.
The Bypass EQ Mux allows the user to bypass all processing. The Bypass EQ mux is at Page 0x21, Register 0x64. The Gang Left / Right mux forces the left processing to be the same as the right processing. The Gang Left / Right Mux is located at Page 0x21, Register 0x68.