3 years back I did a 5.1 channel preamp for TV audio. It uses 3 JRC NJW1119A 3 band tone
control ICs, along with 3 PGA2311 stereo audio control. These chip are all analog with digital
control. If you want to change center frequency of the tone control you need to replace resistors
and capacitors. I also included L & R mono mix and switching to create a center and sub feed
from plain stereo L & R. Control was from an Arduino covering IR remote and local shaft encoder
volume/mute This is all on a 104 x90 mm 4 layer board from JLCPCB and cad work with KiCad 5.x.
That extra 4mm added $27 to the PCB charges but it was still so cheap i didn't care. It works very
well so being DIY, it's time for version 2. This time it's 99.5mm x 89 mm.
Version 2 adds an 8x8 input crosspoint for channel routing. I would prefer Analog Devices for this
but they had been made of unobtainium for many months so instead I'm using a slightly inferior
MT-8808. The PGA2311 gain controls are sill present but at the end of the chain to keep noise down.
The magic is now with ADAU1701 DSP chips which can be 5 band parametric EQ or interface with room
EQ wizard. I will be using a common oscillator for all 4 DSP chips. Since EQ changes are very rare, the
DSPs can all do self boot but it requires the I²C address to be 0. I have an I²C selector to talk directly
to the DSP chips like is done on the Eval board so the local I²C can stay at 0 for self boot. Logic level
translators should prevent damage. Master reset in included. I have the Eval board from Analog Devices
and the tasks I want are do-able. Control is out of Arduino range and will likely be from Raspberry Pi,
maybe Pico or 4.
Power supply is from a 12V external SMPS to a DC-DC converter for the OPAMPS, matrix and gain controls.
The 3.3 Volt DSP supply is an SMPS in a TO-220 footprint, same for the control 5 Volts. What I want here
is take a look at the new version and see if I have done some really dumb mistakes.
The original version 1 is here along with the new version 2.
G²
control ICs, along with 3 PGA2311 stereo audio control. These chip are all analog with digital
control. If you want to change center frequency of the tone control you need to replace resistors
and capacitors. I also included L & R mono mix and switching to create a center and sub feed
from plain stereo L & R. Control was from an Arduino covering IR remote and local shaft encoder
volume/mute This is all on a 104 x90 mm 4 layer board from JLCPCB and cad work with KiCad 5.x.
That extra 4mm added $27 to the PCB charges but it was still so cheap i didn't care. It works very
well so being DIY, it's time for version 2. This time it's 99.5mm x 89 mm.
Version 2 adds an 8x8 input crosspoint for channel routing. I would prefer Analog Devices for this
but they had been made of unobtainium for many months so instead I'm using a slightly inferior
MT-8808. The PGA2311 gain controls are sill present but at the end of the chain to keep noise down.
The magic is now with ADAU1701 DSP chips which can be 5 band parametric EQ or interface with room
EQ wizard. I will be using a common oscillator for all 4 DSP chips. Since EQ changes are very rare, the
DSPs can all do self boot but it requires the I²C address to be 0. I have an I²C selector to talk directly
to the DSP chips like is done on the Eval board so the local I²C can stay at 0 for self boot. Logic level
translators should prevent damage. Master reset in included. I have the Eval board from Analog Devices
and the tasks I want are do-able. Control is out of Arduino range and will likely be from Raspberry Pi,
maybe Pico or 4.
Power supply is from a 12V external SMPS to a DC-DC converter for the OPAMPS, matrix and gain controls.
The 3.3 Volt DSP supply is an SMPS in a TO-220 footprint, same for the control 5 Volts. What I want here
is take a look at the new version and see if I have done some really dumb mistakes.
The original version 1 is here along with the new version 2.
G²
