Help with costume sound effects

[ravennhawke]

I am a semi-novice when it comes to this type of thing, so here it is.......I purchased an adafruit audio board with the 2x2 amp attached. I am using it to add sound to a Darth Vader costume. I have mostly finished the project, however the voice volume is just a little to low. It is adequate but I would like it slightly louder and possibly be able to control the volume with a pot. I am wondering if I can add another amp in series (for example, in the middle of the wires from the board to the speaker) and get a louder sound? if so, which amp(s) would work best? I'm not sure if another amp can handle the audio input that is already amplified. is this even possible?

[adafruit_support_mike]

You don't want to connect the output from the FX Board's 2.2W amp to the input of another amplifier. The signal is high-frequency PWM, which is hard for another amp to read.

You can connect the line output pins on the side of the FX Board (labeled L, R, and GND) to another amp though. The MAX9744 is good and powerful, and gives you the option to control the volume with a pot:

https://www.adafruit.com/product/1752

[ravennhawke]

I like the idea of having 20W, but a speaker to handle that much power is a bit too large for the costume. Could I use the 3.7w MAX98306 the same configuration? I know it wouldn't work with a pot, but I can live without it. Assuming I am able to use the MAX98306, would my final power output just be added together (2.2w plus 3.7W to equal 5.9W) in that configuration?

[adafruit_support_mike]

Sure.. you can even use a couple of 3.7W amps and speakers if you want some secondary boost power.

The MAX98306 doesn't accept volume control from a pot directly, but you can use a pot between the FX Board and the speaker amp to control volume.

Taking the left channel for the sake of discussion, connect the FX Board's L pin to one end of the pot and its GND pin to the other end of the pot. Connect the MAX98306's L- input to the GND end of the pot and its L+ input to the pot wiper. The pot will control the amount of signal coming out of the FX Board that reaches the MAX98306.

The one gotcha is that you need what's called a log-taper pot:

https://www.adafruit.com/?q=log-taper%20pot

The human ear responds to ratios of sound pressure more than absolute changes in pressure. 'Twice as much pressure' sounds like the same increase in volume whether you started from a whisper or a jet engine.

With a normal (linear-taper) pot, the whole upper half of its sweep range is less than 'twice as much signal' relative to the halfway mark. That's only twice as much as the quarter-turn mark, which is only twice as much as the 1/8-turn mark, and so on. Almost all of the audible change in volume will happen way down at one end of the sweep range.

A log taper pot arranges things so you hear a uniform increase in volume across its whole sweep range. The actual signal on the wiper stays low for almost the entire sweep, then spans that last twice-as-much level in the last 1/10th of the sweep range or so.