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Thread: Need help amplify Teensy 4.0 for PA sound

  1. #1
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    Need help amplify Teensy 4.0 for PA sound

    Hello,

    I'm trying to build a microphone that applies voice effects. It will be used for live performances on PA speakers. Right now there is an electret mic hooked up to the mic input on the Teensy 4.0 audio board. The audio output will be routed into a mixer which will then go to loudspeakers.

    I need some help figuring out how to amplify the sound to be loud enough for a big system while also minimizing noise. I think I need an amplifier and a mic preamp to achieve this. Ideally both of these would be breakout boards that can be integrated into the mic unit. However, I'm getting a bit lost trying to figure out the specs for what I need. Here are my questions:

    1) Am I overthinking this? Would it be perfectly fine to use the headphone jack output for this and skip the amp/preamp nonsense?

    2) If #1 is a no, then how powerful does the amplifier need to be? i.e. how many watts should I be looking for?

    3) Would a preamp with gain of 40-60dB help to reduce the input noise?

    4) Is it appropriate to send preamp-ed mic signal to the mic input or should the signal go to the line input?

    Thank you for your help.

  2. #2
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    Do #1 - teensy headphone jack into mixer line input.

  3. #3
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    Thanks for the guidance

  4. #4
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    No, certainly don't use the headphone jack. Its not ground-referenced and the sound quality is lower than the line-outs.

    The line-out pads are what you use to send to an amplifier.

  5. #5
    Senior Member PaulStoffregen's Avatar
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    If this will be used live, usually the biggest problem is feedback from the speakers back into the microphone. Audio feedback is a tough problem common to all live performances. Usually the key to success is good speaker placement and a microphone with directional sensitivity.

  6. #6
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    Another common problem is noise from ground loops. Don't reference to any noisy ground that you don't have to. Use outputs from an isolated teensy+audio adapter as balanced signals into balanced inputs. Leave the teensy otherwise isolated from the mixer.

    Specs on the headphone output and line outs are audibly identical. Except the line-outs have series capacitors (what kind?) which adds some distortion (probably inaudible).

  7. #7
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    There is definitely going to be some experimentation with the mic gain to ensure that it can pick up a human voice close to the mic, but none of the ambient music. I hadn't thought about picking a directional mic. It seems so obvious!

    The ground loops might explain where I'm getting some of my current background noise.

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