Hi Everyone,

I am VERY new to electronics and teaching myself how to put together basic PCBs so forgive me if this is a total flop. My goal with this project is to create a PCB that can act as passive or transparent volume control. I want to be able to plug in my record player to the input jack, control the volume via wifi, and then plug in a set of speakers to the output jack. I am not using op-amps as the speakers and record player already have amps in them and this board is meant to just control the volume without having to physically turn the knob on the speakers. (basically turning my speakers into wifi controlled).

Would anyone be able to review this and tell me if this will work? Or is there any ciritical errors/considerations I am missing here?

Any help is greatly appreciated!

Bob.

 

Wecome to AAC.

The immediate problem I see is that the MCP4231 has an absolute maximum current rating of 2.5mA on any of the PxA, PxW, and PxB pins. Assuming an 8Ω speaker, this would get you about 50µW of power before letting out the magic smoke and muting your volume control permanently.

For attenuating the output of an amplifier, you need a pad that can maintain the impedance and dissipate whatever power isn‘t supposed to end up at the speaker terminals—which could be a lot. The alternative is to use something like the TPA2016D2 from TI.

The TPA2016D2 is a stereo amp with I²C control. You would use a fixed pad on the input if you were using speaker outputs to drive it, and then connect the speakers to the amp. If the power isn’t enough for your speakers, you could use it as a preamp for a larger amp.

The MCP4321 is not an appropriate way to accomplish this, but if you wanted to use it, you could substitute the volume control pots of a suitable amp with the digipots on the chip—that would work as well.

 

There is a whole lot of needed information missing here. What is the amplitude of the signal between the "record player" and the "speakers" that already include amplifiers.
In addition, if your understanding is sufficient so that the drawing attached in post #1 makes sense to you, you do not need any assistance from any of us.

 

The immediate problem I see is that the MCP4231 has an absolute maximum current rating of 2.5mA on any of the PxA, PxW, and PxB pins. Assuming an 8Ω speaker, this would get you about 50µW of power before letting out the magic smoke and muting your volume control permanently.

I guess you missed this in the OP:

the speakers and record player already have amps in them and this board is meant to just control the volume

 

Wecome to AAC.

The immediate problem I see is that the MCP4231 has an absolute maximum current rating of 2.5mA on any of the PxA, PxW, and PxB pins. Assuming an 8Ω speaker, this would get you about 50µW of power before letting out the magic smoke and muting your volume control permanently.

For attenuating the output of an amplifier, you need a pad that can maintain the impedance and dissipate whatever power isn‘t supposed to end up at the speaker terminals—which could be a lot. The alternative is to use something like the TPA2016D2 from TI.

The TPA2016D2 is a stereo amp with I²C control. You would use a fixed pad on the input if you were using speaker outputs to drive it, and then connect the speakers to the amp. If the power isn’t enough for your speakers, you could use it as a preamp for a larger amp.

The MCP4321 is not an appropriate way to accomplish this, but if you wanted to use it, you could substitute the volume control pots of a suitable amp with the digipots on the chip—that would work as well.

So I am only dealing with standard LINE input and output. My record player is an AT-LP60X that outputs line 150mV @ 1kHZ and a 36dB pre-amp. My Speakers are Logitech Z207 that can take 10W Peak and 5W RMS. Assuming theese requirements I only want to be able to control the volume using the ESP over wifi. My biggest concern is just discovering a new type of firework in my living room. As long as it's not going to blow up or seriously degrade audio quality then I'm happy with it.

 

There is a whole lot of needed information missing here. What is the amplitude of the signal between the "record player" and the "speakers" that already include amplifiers.
In addition, if your understanding is sufficient so that the drawing attached in post #1 makes sense to you, you do not need any assistance from any of us.

As I am still learning, I have a basic understanding of the schematic (which I made myself in KiCad), but I mostly referenced Youtube tutorials and ChatGPT so I just want to be sure that I am not missing anything crititcal. Record player is an AT-LP60x Line output of 150mV @ 1kHZ and speakers are Logitech Z207 with input of 10W peak and 5W RMS. Can't find any other data on them as they are sort of a cheaper desktop speaker and no impedance information is given.

 

I would trust the advice of my friend's cats more than any technical advice from chat GPT, based on what I have seen it deliver.

 

I would trust the advice of my friend's cats more than any technical advice from chat GPT, based on what I have seen it deliver.

Haha, yeah that's why I am seeking advice from online forums. Even with my limited electronics knowledge, I noted some questionable things from AI.