Best amplifier to use with a ISD1820

Thread Starter

laserau77

Joined Feb 11, 2018
12
Hi everyone,
I have read a few threads on this topic before and they are great but I have a slightly different question.

I have been given a task of using a ISD1820 to drive an outdoors speaker and I have a week to do it.
If I use it to drive a standard portable Bose speaker the audio quality is actually really good.

I got a small 8 ohm loudspeaker for use outdoors and the output from the ISD1820 board is not enough which was not unexpected.

So I built a amplifier (https://www.jaycar.com.au/the-champion-audio-amplifier-kit-with-pre-amplifier/p/KC5519) and tested it and it does a good job of amplifying the recording but it clips the signal and the voice is not recognisable.

As I am on a short timeline, has anyone used any "off the shelf" audio boards or kits which do a good job of removing noise, static etc?

If I had a few months I would play around with different chips and make a circuit that works great. As I only have a week I am a little pressed to find something that will work great.
I am in Australia.

I look forward to hearing your suggestions.
 

bertus

Joined Apr 5, 2008
21,314
Hello,

The datasheet of the IDS1820 shows a bridged output.
In the datasheet there is a suggested schematic for a more powerfull amplifier.
The datasheet of the AN7511, that is used in the amplifier in the link, shows a single ended input and bridged output.

Bertus
 

Attachments

Audioguru

Joined Dec 20, 2007
11,249
The recording module has an output of 0.5W. The kit amplifier has an output of maybe 1.5 Watts (they say 3 Whats at high distortion) that is not much louder. The bridged AD2511 has an output of only 1W. You need at least 5W to sound twice as loud as 0.5W.
 

Thread Starter

laserau77

Joined Feb 11, 2018
12
Thanks for the feedback guys.
I am thinking down the lines of using a portable speaker like the Bluetooth ones available these days. I don’t neccessarily need the Bluetooth part but they normally have great output and input RC filters etc to remove noise.
Does anyone know of a good brand that will it cost a fortune.
Know price does normally match the quality of the product but for this purpose it needs to work well but not be exceptional quality audio.
 

Thread Starter

laserau77

Joined Feb 11, 2018
12
Hi Guys,
I found a 12W amplifier http://www.altronics.com.au/p/a0720-kemo-12w-plug-and-play-mono-amplifier-module/
to use with the board and they work together great.
Thanks for all your assistance.

Just another question... :)

Do you think it would be ok for me to connect 2 separate ISD1820 directly to the input of this amp? They will both play at different times?

I am in 2 minds about it, my other option is to use a relay to switch the output to the ISD1820 which is playing. This may be the proper way to do it but wanted to see what you guys thought.
What are you thoughts?
 

Reloadron

Joined Jan 15, 2015
5,911
Do you think it would be ok for me to connect 2 separate ISD1820 directly to the input of this amp? They will both play at different times?
You may want to give some thought to a simple audio mixer, there is not much to it. A Google of Basic Audio Mixer circuits will bring up some good material, like this site as an example.You also could go as simple as a SPDT switch as neither will be used at the same time and you only have two channels. Sharing common they could even be switched with a SPDT switch.

Ron
 

Thread Starter

laserau77

Joined Feb 11, 2018
12
Thanks Ron, I have used SPDT relays before and they work great for this use. I don't have any and wanted to get it working quickly so was just wondering if I could get away with it. I better do it properly.
 

Thread Starter

laserau77

Joined Feb 11, 2018
12
I have connected up the ISD1820 Board and have a lot of noise coming through.
The ISD1820 board runs off a 3.3V supply which is a small switch mode power supply.
The noise is generated by the power supply and I am trying to filter it to remove the noise.
See the attached oscilloscope screenshots.
What size decoupling Caps are best to use? 10uF Electrolytic or 1uf Tantalum etc?

Should I think about a RC Filter on the audio output to capture the noise before it hits the amplifier?
upload_2018-2-18_15-57-22.png
 

Audioguru

Joined Dec 20, 2007
11,249
Your main interference frequency is 50Hz probably because you did not connect its audio to the amplifier with shielded audio cable.
The shield blocks AC electricity hum picked up by your wires that act like antennas.
The waves on your 'scope are 20ms apart so the frequency is 1/0.02= 50Hz.
The high frequency hash is the switching frequency that can be filtered out of the power supply voltage.

If you filter the audio output then sounds will be muffled.
 

Hextejas

Joined Sep 29, 2017
187
Your main interference frequency is 50Hz probably because you did not connect its audio to the amplifier with shielded audio cable.
The shield blocks AC electricity hum picked up by your wires that act like antennas.
The waves on your 'scope are 20ms apart so the frequency is 1/0.02= 50Hz.
The high frequency hash is the switching frequency that can be filtered out of the power supply voltage.

If you filter the audio output then sounds will be muffled.
Audio, in coming up with the 20ms apart, did you use the wave at 8ms and 28ms?
The reason that I ask is that I am a noob at reading an oscilliscope so any chance that I get that becomes a teaching moment, I will jump at.
It seems that there is a peak at 22ms also.
thank you and this is not an attempt to hijack the thread.
 

Audioguru

Joined Dec 20, 2007
11,249
Yes, the overall interference waveform occurs every 20ms. The peak at 22ms is also in a repeating 20ms part of the waveform could be caused by fluorescent lights or something electrical distorting the 50Hz electricity.
 
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