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Topic: Amplifying the output of a ISD1820 (Read 2568 times) previous topic - next topic

TwoChain

Hello,

I am having difficulty connecting my ISD1820 board to a LM386 amplifier circuit.

I have built the LM386 amplifier circuit with a gain of 200. I have tried connecting my mp3 player to this circuit, and it is working perfectly. To connect my mp3 player, I am using a 3.5 mm headphone jack. As most people on this forum will know, the headphone jack has three connections that can be made. One connection is for the left speaker, one is for the right speaker (for a stereo configuration), and one is ground. Since the LM386 circuit I have built is a mono amplifier (not stereo), when I connect my mp3 player to the LM386 circuit I connect only one of the inputs from the headphone jack (either the left or right), and the ground, to the LM386 circuit.

This is all fine and well, and as I said, it works perfectly. However, when I try to connect the ISD1820, nothing happens. Here is a link to the ISD1820 board I am using: http://www.elecfreaks.com/2215.html. In the instructions, it is stated that this board can be connected to a LM386 circuit. I believe they are saying to connect one speaker output from the ISD1820 to the input for the LM386 circuit, while leaving the other speaker output from the ISD1820 empty. I have tried this, but it does not work. I have also tried the FT switch but this does not help (although I'm not entirely sure what FT does...).

My questions are:

1) Do you believe I am reading these instructions correctly; should I only connect one speaker output from the ISD1820 to the input of the LM386 while leaving the other output from the ISD1820 empty?
2) Has anyone ever successfully combined a ISD1820 board with a LM386 amplifier?

I really appreciate any help you can provide.

Thank you,

Dustin


elac

You have to connect both wires from the ISD1820 output to the LM386 amp input.
The ISD1820 is mono.
With FT switched you should be able to speak through the mic and have it come directly through the speaker.
It's all about the skills

TwoChain

Hello,

Thank you for your reply. To be clear, you are suggesting that I connect the speaker output terminals from the ISD1820 together, and then connect these to the input of the LM386 circuit?

Thanks,

Dustin

elac

Don't connect the wires together.
One wire from the ISD1820 output goes to the LM386 input and the other wire from the ISD1820 goes to ground.
If they are powered separately make sure that the amp circuit and the ISD1820 share a common ground.
I read quickly and thought you were using an LM386 module.
It's all about the skills

TwoChain

Hi,

Thanks for the suggestion. I'll try this and let you know if I have any success.

Dustin

elac

It's all about the skills

TwoChain

Hi,

I just tried your suggestion. Unfortunately, I am still not getting any sound. When I connect my speaker directly to the ISD1820 board, I can hear my recording perfectly. I am therefore confident that the ISD1820 is working. However, when I connect my speaker to the LM386 circuit, and try to feed the output from the ISD1820 to the input of the LM386 circuit, I don't get proper playback. When I press play on the ISD1820, I can hear a change in the frequency of the buzzing from the speaker connected to the LM386, but I don't get any audio.

Any other suggestions?

Thanks,

Dustin

elac

#7
Sep 03, 2013, 04:47 am Last Edit: Sep 03, 2013, 05:10 am by elac Reason: 1
Did you try the second circuit posted on the ISD1820 web page?
Are both circuits powered from the same source?
If not, are the grounds connected?
I tried it with a LM386 module and had to leave one of the outputs of the ISD1820 disconnected.


It's all about the skills

TwoChain

Hello,

I have not tried the second circuit yet.

I am powering both circuits from the same source, and both the ISD1820 and the LM386 have the same ground.

I also have a pre-assembled LM386 module and I am having no success with it either. I have tried this without connecting one of the ISD1820 outputs (as they seem to suggest in the ISD1820 instructions in the original link I posted), and with connecting the second output to ground (as you suggested I try).

From your post, it sounds like you have successfully used the LM386 (pre-assembled module) to amplify the output of the ISD1820 board. Is this true? If so, do you mind taking a picture of your connections. I have been working on this for awhile and it is driving me crazy.

Thanks,

Dustin

elac

Works fine with my LM386 module.
Here's a pic of the connections:
http://www.sendspace.com/file/9zms1k
It's all about the skills

TwoChain

Thank you very much for taking this picture, I really appreciate it.

You have exactly the same modules as me, so it is very relieving to hear/see that you are having success. The only thing I can think of now is that maybe my speaker is not working properly. My final question for you is: what are the specs on the speaker you are using?

Thanks again for all of your help.

Dustin

elac

If your speaker works from the ISD1820 it should work from the LM386 amp.
My speaker is  2",  8ohm  and 1/2 watt.
It's all about the skills


elac

Try this Dustin,
Flip the FT switch on the ISD1820 to the right. Turn the pot on the LM386 all the way to the left(towards the VCC pin on the LM386 module) speak through the mic and at the same time slightly turn the pot to the right until you hear your voice through the speaker.
It's all about the skills

TwoChain

Hi Elac,

I did as you suggested, and I had success! Thank you for your help. However, I now have a few more questions:

1) When I connected the LM386 and ISD1820 as you described, I can only get audio from my speaker when the potentiometer on the LM386 is in precisely the correct position. Why is this? I thought I would be able to control the volume by adjusting this potentiometer. Instead, it is basically on, or off.

2) When I have the potentiometer turned to the correct position to get some audio, it is very quite. How can I use my LM386 to actually increase the volume?

Thank you,

Dustin

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