PaulStoffregen
Well-known member
Well, if you use the audio shield with its default output range of 1.33 Vp-p, then you'd need a gain of 2.14 to get to 3.47 Vp-p (which is +4 dBu level used by most pro gear).
If you use that LM386 circuit with 20X gain, you'd need to set the pot to attenuate the signal nearly a factor of 10 to get the right output level. Aside from the low quality of the LM386 amplifier, so much attenuation followed by so much gain is a recipe for adding quite a lot of noise.
Of course you could configure the SGTL5000 to output a higher signal. If you care about quality, avoid the highest few settings. Perhaps use the 2.67 Vp-p setting. Then you'd need a gain of only 1.3. You could get that with a high quality NE5532 opamp (commonly used for professional quality audio). You could get that gain with the normal non-inverting circuit, using a 1K and 3.3K resistor.
Or if you really want to make the circuit adjustable, you could use a pot to attenuate the signals, and then a gain of 2 or perhaps 3 with the opamp circuit. That'd let you reach 8 Vp-p, assuming your NE5532 opamp is powered by supplies at least +6V and -6V.
If you use that LM386 circuit with 20X gain, you'd need to set the pot to attenuate the signal nearly a factor of 10 to get the right output level. Aside from the low quality of the LM386 amplifier, so much attenuation followed by so much gain is a recipe for adding quite a lot of noise.
Of course you could configure the SGTL5000 to output a higher signal. If you care about quality, avoid the highest few settings. Perhaps use the 2.67 Vp-p setting. Then you'd need a gain of only 1.3. You could get that with a high quality NE5532 opamp (commonly used for professional quality audio). You could get that gain with the normal non-inverting circuit, using a 1K and 3.3K resistor.
Or if you really want to make the circuit adjustable, you could use a pot to attenuate the signals, and then a gain of 2 or perhaps 3 with the opamp circuit. That'd let you reach 8 Vp-p, assuming your NE5532 opamp is powered by supplies at least +6V and -6V.
