Sharing A Speaker With An DY-SV19T For MP3 Files And ESP32 For Tone

[JohnWin]

Hello, I have a project in which I'd like to use the DY-SV19T to play mp3 files and also use an ESP32 to play tones through the same speaker. When I hook them both up to the same speaker the DY-SV19T plays fine but the ESP32 doesn't play the tone.

I found if I put a 10ohm resistor between the - of the speaker and the ground of the ESP32 they both play fine. But when the DY-SV19T plays an MP3 file the resistor gets very hot quickly. I put several resistors in parallel equalling 10ohms which slows down the heat, but this isn't an ideal solution.

I hoping to get some insight into this problem here. Any ideas as to what the cause of this is or potential solutions would be greatly appreciated.

 

[kellys_eye]

Schematic?

There's a class-d audio amplifier chip on that board (assuming I'm looking at the right thing). If you can identify the chip type you should be able to access the input (audio) pin and apply the signal from your ESP32 at that point (using a suitable series resistor) and the audio will be presented as it's supposed to be.

 

[JohnWin]

Thanks Kellys_eye, Im attaching a very crude schematic.

I considered going through the amp on the DY-SV19T previously but decided against it because the pins are really small and I was hoping to make and sell these when I'm done.

Thanks again for the thought!

 

[kellys_eye]

Nope, you can't do that! The class-d amplifier has a 'balanced' output i.e. neither side is referenced to ground and your resistor is effectively shorting one side of the drive circuitry. You will damage it!

Equally you will be applying a voltage to the output port of the ESP32 (the driven pin sending the signal) which could also cause damage (less likely).

The only practical, safe and workable way is to do as I previously suggested. Small as the pins are they aren't impossible to solder to!

 

[JohnWin]

Ok, thanks for letting me know! I had no idea I was doing that.

I'll put on my magnifying glasses and see what I can do. I'll report back and let you know how it goes.

 

[JohnWin]

Nope, you can't do that! The class-d amplifier has a 'balanced' output i.e. neither side is referenced to ground and your resistor is effectively shorting one side of the drive circuitry. You will damage it!

Equally you will be applying a voltage to the output port of the ESP32 (the driven pin sending the signal) which could also cause damage (less likely).

The only practical, safe and workable way is to do as I previously suggested. Small as the pins are they aren't impossible to solder t

I managed to successfully solder a wire to the input pin.

I'm not sure how to determine an appropriate series resistor but saw there was already a 100k going to it. So I tried that. When I fired everything up I got a lot of strange noises. I unplugged the tone and the mp3s are playing fine.

I suspect I didn't use an appropriate resistor. How should I go about determining the right value resistor? I should have asked before but was hiding my ignorance.

 

[kellys_eye]

What are the code numbers on the tops of the two 8-pin devices?

 

[JohnWin]

The top number is:
LTK5128D
and below that is:
2445KK
and another I have the bottom is:
250BKK

I found this if it helps:

 

[JohnWin]

Those were the numbers for the amp. On the other 8-pin device the numbers are:
25032BSSIG
2244

 

[JohnWin]

What are the code numbers on the tops of the two 8-pin devices?

Here's a picture incase I got any of the numbers wrong. It's hard to tell if they are 8's or B's and I's or 1's.

 

[JohnWin]

I just realized that I wrote the wrong module in the post. I have the DY-SV17F, not the DY-SV19T.

 

[kellys_eye]

You can apply a second audio signal to the chip but add a DC blocking capacitor to the output of your ESP32 (pin 32). A 100nF capacitor will do.

 

[JohnWin]

You can apply a second audio signal to the chip but add a DC blocking capacitor to the output of your ESP32 (pin 32). A 100nF capacitor will do.

Thanks for all of your help with this! I tried the DC blocking cap inline from pin 32 directly to the chip but I just get clicking sounds when I power up.

It's not terribly important that the tones play over the MP3s. So, I'm wondering if I put a J3Y transistor on the ground from the speaker to ground (where the 10ohm resistor was) and switch it off when an MP3 is playing if that would work. I believe I have two extra pins on the ESP32 so could put one on the speaker ground of the module too. And just switch between them depending on which is playing.

Do you think it's worth a shot or will I still be potentially damaging things?

 

[kellys_eye]

I tried the DC blocking cap inline from pin 32 directly to the chip but I just get clicking sounds when I power up.

I din't know what form your signal from the ESP is - mark-space ratio, frequency etc so the capacitor value may need to change - try 10uF and a series resistor (100k). Does the ESP output still work?

You should not ground either side of the speaker signal else you will damage the audio chip.

 

[JohnWin]

I din't know what form your signal from the ESP is - mark-space ratio, frequency etc so the capacitor value may need to change - try 10uF and a series resistor (100k). Does the ESP output still work?

You should not ground either side of the speaker signal else you will damage the audio chip.

Hi Kellys_eye, I tried a 10uf with a 100k resistor and the results were much better but not perfect. The MP3s cut in and out when they first start to play. And the tone which is supposed to pulse and play at different frequencies is also good sometimes but turns into a solid tone at times.

I tried a couple of 10uf caps in parallel and series but it got worse.

After a little consideration, I think it would be easier to just use two speakers. Soldering to the amp pin is a pain and those little 3w speakers are only $1-2.

I really appreciate the time you spent helping me. I wish I had a better outcome for you.

Take care! And best of luck!