Modular Audio Project - Amplifier Module

An class D amplifier module that can select other digital sources (I2S, S/PDIF).

System Diagram

Functional Components

flowchart LR

main_ctrl["Main Controller"] -- Parallel Bus --- i2sm[I2S-Multiplexer];
wifi --- antenna1((Antenna <br> 1));

main_ctrl -- I2C --- dsp;
main_ctrl -- SPI+2 --- wifi["WiFi Co-Processor"]
i2sm -- I2S --- dsp["Digital Signal <br> Processor"] -- I2S --- amp[Amplifier];
dsp -- I2S --- toslink_out_converter[TOSLINK<br>Converter] -- "S/PDIF" --- toslink_out{{TOSLINK <br> Out}};


style dsp stroke-dasharray: 5 5;
style toslink_out_converter stroke-dasharray: 5 5;
style toslink_out stroke-dasharray: 5 5;


subgraph sources [Sources-In]
    cd{{CD}};
    dvd{{DVD}};
    tos_link_in{{Toslink In}}
end

subgraph source_sel_display [Source Selection Lights]
    direction LR
    cd_source_selected((CD ))
    dvd_source_selected((DVD))
    bluetooth_source_selected((BT ))
    wlan_source_selected((WLAN))
    dab_source_selected((DAB))
end

antenna2((Antenna <br> 2)) --- airlink;
airlink["Airlink/Bluetooth"] -- I2S --- i2sm
cd -- I2S  --- i2sm;
dvd -- "S/PDIF" --- spdif["S/PDIF Module"] -- I2S --- i2sm;
internet-radio["Internet Radio"] -- I2S --- i2sm

tos_link_in -- "S/PDIF" --- toslink_converter[TOSLINK<br>Converter] -- I2S --- i2sm; 
dab["DAB Radio"] -- I2S --- i2sm

amp --- left{{Left}} --- left_spk((Left <br> Speaker)) 
amp --- right{{Right}} --- right_spk((Right <br> Speaker)) 

dsp -- I2S --- sw-dac[Sub-Woofer DAC] --- sw-line-out{{Sub-Woofer<br>Line-Out}} --- active-sw((Active<br>Sub-Woofer))


vol_proc[Volume <br> Processor];
sel_source[Select <br> Source <br>];

subgraph controls[Controls]
    direction TB
    sel_source_btn((Select <br> Source Button))
    vol_knob((Volume <br> Knob))
end

sel_source --- source_sel_display
vol_knob --- vol_proc -- I2C+1--- main_ctrl;
sel_source_btn --- sel_source -- I2C+1--- main_ctrl;


%%click main_ctrl "https://github.com/adoble/modular-audio/blob/main/README.md#controller"%%
%%click i2sm "https://github.com/adoble/modular-audio/tree/main/hardware/i2s-multiplexer" "Click to see sub-repository"%%

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Power

    graph LR;

    net{{240V AV}};
    net ---- Relay;
    Relay --- smps[Switched Mode <br> Power Supply];
    smps ---- pwr_24v{24V};
    smps --- reg_5v[5V Regulator];
    smps --- reg_3v3[3.3V Regulator];
    reg_5v --- pwr_5v{5V};
    reg_3v3 --- pwr_3v3{3.3V};

    Battery --- pwr_on_off(("Power <br> On/Off <br> Switch")) --- Relay; 

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Symbols used in the Diagrams

graph LR;

subgraph key[Key]
    transducer((<small>Transducer<small>)) ---  pwr_net{<small>Power<br>Net<small>} --- module[<small>Hardware Module<small>] --- ext{{<small>External<br>Connection<small>}};
end
style key stroke-dasharray: 5 5, fill-opacity: 0;

%% Render links invisible
linkStyle 0 stroke:none
linkStyle 1 stroke:none
linkStyle 2 stroke:none

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Functional Component Descriptions

Controller

Work in Progress!

The controller has the following tasks:

• Select sources
• Receive input fron the volume control and adjust the volume over the DSP.
• Receive input from the button banks. These are used to interact with the display.
• Interface with an (Airlift) Wifi board over an extended SPI interface. This is used to download station lists and also to control the internet radio module.

Software is here.

Hardware is here.