Hi All,
I am a total noob at electrionics and audio gear. I'm hoping to learn some new stuff by working on this first project. Basically I have an Audio Technica LP60X that outputs a signal at around 36dB LINE (100mV @ 1kHz) and currently it goes to a set of Logitech desktop speakers with a max input rating of 10W and a continuous rating of 5W RMS. (I know its probably an insulting setup to any harcore audiophiles but Im working on a budget).
My goal is to create an ESP32-S3 Mini 1 controled PCB, which will act as passive volume control in between the turn table and speakers. It does not need to amplify the signal, just be able to fade out and then fade back in using the ESP's wifi function and a digital potentiometer. I did some consulting (chatGPT and Youtube) and settled on using the MCP4231 as it seems to be the only chip that can handle stero input with single power supply and SPI control. (its also cheap).
The plan here is something like this: Audio from record player --> Passive Wifi-enabled volume control --> Speakers
I have attached a schematic I drew up in KiCad. Would you be able to look it over and let me know if there are any crucial errors I might be missing? Also if you have any tips/tricks or recomendations that would be appreciated too.
Kiitos! (Thank you so much in Finn)
Joel.
I am a total noob at electrionics and audio gear. I'm hoping to learn some new stuff by working on this first project. Basically I have an Audio Technica LP60X that outputs a signal at around 36dB LINE (100mV @ 1kHz) and currently it goes to a set of Logitech desktop speakers with a max input rating of 10W and a continuous rating of 5W RMS. (I know its probably an insulting setup to any harcore audiophiles but Im working on a budget).
My goal is to create an ESP32-S3 Mini 1 controled PCB, which will act as passive volume control in between the turn table and speakers. It does not need to amplify the signal, just be able to fade out and then fade back in using the ESP's wifi function and a digital potentiometer. I did some consulting (chatGPT and Youtube) and settled on using the MCP4231 as it seems to be the only chip that can handle stero input with single power supply and SPI control. (its also cheap).
The plan here is something like this: Audio from record player --> Passive Wifi-enabled volume control --> Speakers
I have attached a schematic I drew up in KiCad. Would you be able to look it over and let me know if there are any crucial errors I might be missing? Also if you have any tips/tricks or recomendations that would be appreciated too.
Kiitos! (Thank you so much in Finn)
Joel.
Hi Joel,
For someone who says they are a total noob at electronics, how are your programming skills? A lot of complication for a volume control but you want network controlled remote volume control so it comes at a big cost.
I have never used esp32 so not much help from me.
Are those pins that USB data is connected too, 5V compatible?
What’s the purpose of Q1, 1.56Vref?
Might want to have this thread moved to the electronic design section for more exposure.
Good luck
Rick
For someone who says they are a total noob at electronics, how are your programming skills? A lot of complication for a volume control but you want network controlled remote volume control so it comes at a big cost.
I have never used esp32 so not much help from me.
Are those pins that USB data is connected too, 5V compatible?
What’s the purpose of Q1, 1.56Vref?
Might want to have this thread moved to the electronic design section for more exposure.
Good luck
Rick
Last edited:
Please explain how you control the volume.
Phone app? Remote controller?
I'm sadly ignorant of ESP32.
You may want to add an OLED display or an LED bar graph to show the volume setting.
Consider whether to save last setting or start from a preferred setting to avoid surprises if you left on full volume when shutting down.
The turntable phono is curious with low 100 - 150mV output.
Good luck.
Phone app? Remote controller?
I'm sadly ignorant of ESP32.
You may want to add an OLED display or an LED bar graph to show the volume setting.
Consider whether to save last setting or start from a preferred setting to avoid surprises if you left on full volume when shutting down.
The turntable phono is curious with low 100 - 150mV output.
Good luck.
I have a background in software engineering so programming wise I should be just fine. Q1 is a MOSFET to completely drain the board if the tempurature exceeds a certain value. The 1.65Vref is a reference bus for the P0B and P1B pull downs (I noticed I accidentally connected these to GND in the image but they should go to the split rail). My concern here is more or less if I will see a significant loss in audio quality or damage any of my existing equipment.
Hello!
From what you have mentioned, I understand that the digital part of your project is ok for you (microcontroller, USB interface etc).
I never used the MCP4231, but I took a look on its datasheet.
From audio point of view, The analysis is very simple.
The MCP4231 will basically provide you 2 potenciometers based on resistors and analog switches controlled by a logic to mimic a potentiometer.
I think there is no audio loss due to the fact that you are playing with resistors only, so a passive circuit (pay attention to possible digital interference).
The emulation of the potenciometer will happen by connecting the resistors through the analog switches that will be on or off only.
Regarding damage to your audio equipment, you need to make sure the impedance presented to the output of it will not be less than expected minimum. This impedance is the resistance seen between P0A and P0B. This will be the impedance seen by the output audio device. In general, it should not be less than 10Kohm. Most line equipment can handle 10kohm.
You can share with us which are the equipment you plan to use with this circuit for better analysis.
Have you already mapped how this resistor array will be configured? I suppose you must build this map for creating the logic anyways.
Share here when you have this map so we can give you an opinion, mainly what will be the resistance from P0A to P0B.
From what you have mentioned, I understand that the digital part of your project is ok for you (microcontroller, USB interface etc).
I never used the MCP4231, but I took a look on its datasheet.
From audio point of view, The analysis is very simple.
The MCP4231 will basically provide you 2 potenciometers based on resistors and analog switches controlled by a logic to mimic a potentiometer.
I think there is no audio loss due to the fact that you are playing with resistors only, so a passive circuit (pay attention to possible digital interference).
The emulation of the potenciometer will happen by connecting the resistors through the analog switches that will be on or off only.
Regarding damage to your audio equipment, you need to make sure the impedance presented to the output of it will not be less than expected minimum. This impedance is the resistance seen between P0A and P0B. This will be the impedance seen by the output audio device. In general, it should not be less than 10Kohm. Most line equipment can handle 10kohm.
You can share with us which are the equipment you plan to use with this circuit for better analysis.
Have you already mapped how this resistor array will be configured? I suppose you must build this map for creating the logic anyways.
Share here when you have this map so we can give you an opinion, mainly what will be the resistance from P0A to P0B.