Connecting LM386 to ISD1820


I recently purchased a LM386 chip (for amplifying) and an ISD1820 (voice recorder). I had hoped it would be simple to connect the two together, but I am having difficulty figuring out how to do this. I cannot find any clear documentation on these two boards, and thus all of my attempts to join them together has not worked. The best/only description I could find was: However, I have not found this link to be very helpful.

For the LM386 board, I believe the pins are fairly self explanatory.

Link to the LM386 board I have purchased:

1) "GND" = ground 2) "GND" = ground (again) 3) "IN" = input signal (this is the pin I'm not positive I know what to do with) 4) "VCC" = VCC (obviously)...

I am then connecting a 8 ohm 0.25 W minispeaker to the speaker connections on the LM386 board.

Link to the ISD1820 board I have purchased:

For the ISD1820 board, I have tried switching the "FT" switch to either position, and connecting the "FT" pin to the "IN" pin of the LM386 board. The only other pins on the ISD1820 board that I am currently using are the "VCC" and "GND" pin. After making these connections, I press the "PLAYE" button on the ISD1820, but I am not getting any audio (I have already recorded audio with my ISD1820 board, and verified that it works).

If anyone has any experience with these boards, or any suggestions as to how I can make this work, I would be very grateful.

Thank you,


THe ISD module includes a power amplifier already - see the speaker output terminals. You may connect your 386 amplifier (its input) to IDS's speaker output terminal (it does not matter which one) via 10uF capacitor, for example. Connect the both grounds together as well.

Hello Pito,

Thank you for your reply. I'm not sure where the power amplifier you are referring to is on the ISD board.

However, if I understand your post, are you suggesting that I connect the "IN" pin of my 386 directly to one of the green speaker outputs of my ISD1820 via. a 10 uF cap? If so, I will give this a try and let you know what I find.



I'm not sure where the power amplifier you are referring to is on the ISD board.

The link you have posted lists: .On-chip 8? speaker driver That is the "power amplifier" :) On the schematics there you may see an 8ohm speaker connected to the chip.

Hello Pito,

Thank you for your help. I tried connecting the "IN" pin of my 386 to the speaker terminal of the ISD1820 via. a 10 uF cap. but this had no effect. Also, I now see you are looking at the "ElecFreaks" link, which is where it lists the speaker driver (sorry, I was looking at the ebay link, so I wasn't sure where you were seeing this).

Should I not be connecting my speaker to the input pins of my LM386, and then somehow connecting this board to the ISD1820? Sorry for the confusion, but I am really lost here as to why this is not working.


I tried connecting the "IN" pin of my 386 to the speaker terminal of the ISD1820 via. a 10 uF cap. but this had no effect.

Does you 386 amplifier work? (when you touch the IN input with screwdriver (and set max signal with the pot-trimmer) you have to hear the hum from the speaker). Do you have grounds connected together?

Try to connect your speaker to the "speaker" terminals of the ISD.

Hello Pito,

I tried your suggested test of the 386, and it definitely makes a humming sound so I'm sure it is working.

I have the grounds connected to ground.

If I connect my speaker to the terminals of the ISD, I get audio. The problem is that the audio just never seems to amplify.


I don't think the SP- is true ground. Try using separate power supplies.

Did you get this to work? If so can you please add in a solution because I have the same issue.

For those that come here, found a somewhat useful project and a pretty good usage sheet

Hello All,

I also started another thread that was far more useful for me in the end. Here is the link:

I did this awhile ago, and I apologize for any inconvenience from starting a new thread on this topic. I can't actually recall why I thought it was necessary to do so...