Amplification question Audio FX Sound Board

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DuckAndCover
 
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Amplification question Audio FX Sound Board

Post by DuckAndCover »

I have two projects that require sound files to be played by triggers.
1st. audio file is played through an old telephone hand set speaker. The switch will happen when the handset is picked up, wondering if the Audio FX Sound Board without the amp is enough to power the small speaker in the handset. If I use the one with the 2w amp is the gain adjustable?

2nd project is to use triggers(switches) in a pinball machine to play sound files. since pinball machines are loud and noisy I need to amplify the signal quite a bit. Is there a problem with using powered speakers or adding an external amplifier to the Audio FX Sound Board?

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adafruit_support_mike
 
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Re: Amplification question Audio FX Sound Board

Post by adafruit_support_mike »

DuckAndCover wrote:wondering if the Audio FX Sound Board without the amp is enough to power the small speaker in the handset.
It depends on the speaker's impedance. If it's an original phone speaker, it was probably designed to run from 90v and the impedance could be pretty high.
DuckAndCover wrote:If I use the one with the 2w amp is the gain adjustable?
There are some technical differences between volume and gain, but you can adjust the volume.
DuckAndCover wrote:Is there a problem with using powered speakers or adding an external amplifier to the Audio FX Sound Board?
You can connect the version with headphone output to a powered speaker or external amp. The version with the 2W amp uses a bridged class-D amplifier, so you can't connect that to an external amp without additional filtering.

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DuckAndCover
 
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Re: Amplification question Audio FX Sound Board

Post by DuckAndCover »

Thank you for clearing this up. It sounds like the Audio FX Sound Board without audio amplification ( using an external amp) would work with the pinball project and the Sound Board with the amplification will work in the phone handset if I replace the ear speaker with a low impedance one. As along as I can turn down the volume to the correct level as not to be harmful having the speaker next to your ear. Could also set the sound level in the audio file to low as an option. Sounds correct ?

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adafruit_support_mike
 
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Re: Amplification question Audio FX Sound Board

Post by adafruit_support_mike »

Sounds right.

For the phone, try an 8 ohm speaker first. That's a decent midpoint between volume and power consumption, and is about the highest impedance you can drive efficiently from a 5v supply.

For the pinball machine, just about anything goes. You might end up needing a car stereo amp and speakers.

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DuckAndCover
 
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Re: Amplification question Audio FX Sound Board

Post by DuckAndCover »

Interesting results when using the Adafruit Audio FX Sound Board + 2x2W Amp - and the old handset phone speaker. The sound is very loud and clear. Although, when not playing an audio file, I can hear speaker hiss . The speakers in the old rotary dial phones may be built in a way that also amplify? I do not mind it as long as this would not be harmful to the board.

I could also use a 5ohm resistor and 10uf cap to create a filter ?

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adafruit_support_mike
 
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Re: Amplification question Audio FX Sound Board

Post by adafruit_support_mike »

I wouldn't be at all surprised to get some hiss from old speakers, but it might also be a known glitch in the amp itself. Do you still hear the hiss if you connect the amp to a modern 8 ohm or 4 ohm speaker?

It also might be residue from the PWM frequency, and if so, filtering would get rid of it. The speaker is supposed to do that anyway, but if its impedance is high enough it might not be doing the whole job. Try connecting a non-polarized capacitor across the speaker inputs and see if that does any good. Start around 100nF, increase the value if you still get a hiss, and decrease the value if the output starts sounding muddy.

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