Audio FX Mini Sound Board, plays light static until sound is triggered for the first time

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AnnaTemp
 
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Audio FX Mini Sound Board, plays light static until sound is triggered for the first time

Post by AnnaTemp »

Hi,

All is working as expected on my Audio FX Mini Sound Board, however, it plays very light static until triggered for the first time. After the first trigger, it is silent in between triggers and works as desired. If I power off and repower, it goes back to static. I've trashed and emptied any sound files except my intended files from the board. Any hints?

thank you!
Anna

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adafruit_support_mike
 
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Re: Audio FX Mini Sound Board, plays light static until sound is triggered for the first time

Post by adafruit_support_mike »

Does the FX Board drive the speaker directly, or do you have an amplifier between them?

Post a photo showing your hardware and connections and we'll take a look. 800x600 images usually work best.

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AnnaTemp
 
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Re: Audio FX Mini Sound Board, plays light static until sound is triggered for the first time

Post by AnnaTemp »

Amplifier between them. The static is pretty quiet. But it's definitely different than the silence after the sound plays for the first time. Image
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adafruit_support_mike
 
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Re: Audio FX Mini Sound Board, plays light static until sound is triggered for the first time

Post by adafruit_support_mike »

AnnaTemp wrote: Wed Nov 16, 2022 8:24 pm Amplifier between them. The static is pretty quiet. But it's definitely different than the silence after the sound plays for the first time
Thanks. There's a good chance the static is open-line noise: random fluctuations of current on the input lines until the FX Board asserts an output.

It's a symptom of the FX Board's output lines being held at high impedance before they're actively generating output. That allows parasitic currents and thermal noise to create a noticeable voltage between the pins. That voltage goes through the output amp and turns into a low-level hiss.

Try putting a 1k resistor between the L and R outputs. That will hold the voltage between them near 0V for noise-level currents (usually less than 1uA) while still being easy for the FX Board's output to drive. If that works, you can increase the resistor value until the noise starts to appear again.

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AnnaTemp
 
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Re: Audio FX Mini Sound Board, plays light static until sound is triggered for the first time

Post by AnnaTemp »

Ok I will try it! Thanks!

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AnnaTemp
 
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Re: Audio FX Mini Sound Board, plays light static until sound is triggered for the first time

Post by AnnaTemp »

I bought this product: https://www.adafruit.com/product/4294, used it to connect L+ output to L- output (not using R output at all), and that solved the problem. Thanks! I'm not using a battery or power bank. Is there still a reason to change the resistor value or is it ok to just keep this set up?

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adafruit_support_mike
 
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Re: Audio FX Mini Sound Board, plays light static until sound is triggered for the first time

Post by adafruit_support_mike »

Sticking with 1k is fine.

The FX Board's output is designed to drive 30-Ohm headphones. That means the L and R outputs can handle about 100mA each. The 1k resistor between L+ and L- will only draw 3mA to 4mA, which won't be any problem at all.

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swvonholzen
 
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Re: Audio FX Mini Sound Board, plays light static until sound is triggered for the first time

Post by swvonholzen »

I have soldered and put together over a few years many FX and FX mini soundboards. I have always had this same issue with that static sound when first powered on. But, I am not an electronic-wise kid, and although I can guess how the solution is done, I would like someone to confirm exactly how do I connect the 1K resistor to the two pin terminal blocks where I connect my speaker wires. And/Or can I solve this issue by instead connecting the resistor to the boards SIDE R L speaker connections? Thank you

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Re: Audio FX Mini Sound Board, plays light static until sound is triggered for the first time

Post by adafruit_support_mike »

swvonholzen wrote: Mon Dec 26, 2022 10:52 pm I would like someone to confirm exactly how do I connect the 1K resistor to the two pin terminal blocks where I connect my speaker wires.
There aren't many restrictions. Sticking the leads of a resistor in the terminal blocks with the signal wires would work, though the mechanical stability of the terminal connections could get a bit flaky. Soldering the signal lines to the resistor's leads, then sticking the leads in the terminal blocks would be a little more stable.
swvonholzen wrote: Mon Dec 26, 2022 10:52 pm And/Or can I solve this issue by instead connecting the resistor to the boards SIDE R L speaker connections?
Yeah, that will work too.

There's very little risk in this addition to the circuit. Anything that makes a reliable electrical and mechanical connection between the signal wires and the resistor leads will be fine.

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swvonholzen
 
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Re: Audio FX Mini Sound Board, plays light static until sound is triggered for the first time

Post by swvonholzen »

Mike,
Thank you for your help.
Scott

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swvonholzen
 
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Re: Audio FX Mini Sound Board, plays light static until sound is triggered for the first time

Post by swvonholzen »

Adding 1k resistors to the FX sound board solved the static sound when first powered on.
Thank you Adafruit
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