interference with tpa2012 amp

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dgeorgeton
 
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interference with tpa2012 amp

Post by dgeorgeton »

hello,

i'm working on hooking up some surface transducers to a tpa2012 amp, and i've been getting a lot of static through the transducers. after a lot of playing around, i found that touching the amplifier's open aaa battery pack with my hands makes the static go away, so i can get a clear signal. i'm pretty new to all of this, and can't really figure out why this is or how to fix it. could anyone shed light on why this might be happening? thanks so much in advance! i can post pictures or video of the setup if needed!

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adafruit_support_mike
 
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Re: interference with tpa2012 amp

Post by adafruit_support_mike »

That sounds like you have a floating voltage somewhere. Post a photo showing your hardware and connections and we'll take a look. 800x600 images usually work best.

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dgeorgeton
 
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Re: interference with tpa2012 amp

Post by dgeorgeton »

thanks so much for your help! here are a couple of photos:
IMG_1331.jpg
IMG_1331.jpg (220.43 KiB) Viewed 124 times
IMG_1330.jpg
IMG_1330.jpg (187.08 KiB) Viewed 124 times

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dgeorgeton
 
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Re: interference with tpa2012 amp

Post by dgeorgeton »

and, here's a drawing since these photos weren't the clearest:
amp_diagram.png
amp_diagram.png (568.97 KiB) Viewed 120 times

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adafruit_support_mike
 
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Re: interference with tpa2012 amp

Post by adafruit_support_mike »

Check the leads from the battery pack where they go into the breadboard. Are you using any kind of connector or terminator there?

Battery pack leads are usually made from stranded wire because it's more flexible than solid wire, but it's really hard to make stranded wire get a good connection in a breadboard.

If you don't have solid terminals on the battery pack leads, try soldering a short piece of solid wire to the end of each lead, and press that into the breadboard. Wire gauges between 18 and 24 work pretty well for breadboarding.

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dgeorgeton
 
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Re: interference with tpa2012 amp

Post by dgeorgeton »

thanks for your help!

this battery pack has the stranded ends soldered into solid ones; but unfortunately, i have the same problem with a soldered permaproto build that i have.

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adafruit_support_mike
 
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Re: interference with tpa2012 amp

Post by adafruit_support_mike »

Okay, the next most likely suspect would be the power capacity of the AAA battery pack.

Speakers use a lot of current, and that can produce voltage spikes if the batteries can't keep up with the demand. If the spikes get big enough, the TPA2012 could shut down for a moment and then start up again. That would produce random on/off pulses in the current to the speakers, which would match the noise you're hearing.

Try connecting a larger battery or power supply, or disconnecting one speaker. The first will give the speakers more power, and the second will reduce the current load. See if either of those helps with the output.

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dgeorgeton
 
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Re: interference with tpa2012 amp

Post by dgeorgeton »

thanks for your response! i just tried the two things: first disconnecting one speaker, but the static continued. i reconnected it and replaced the aaa battery pack with a 9v battery, which made the static significantly quieter, but didn't cause it to go away.

i also tried adding in some electrolytic capacitors, but not to much avail.

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adafruit_support_mike
 
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Re: interference with tpa2012 amp

Post by adafruit_support_mike »

Try a 3-AA or 4-AA pack.

9V batteries have fairly high internal resistance, which makes them iffy for high-power operation. Many of them are made from a 6x array of AAAA cells, which are weaker than AAAs.

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