ISD1820
Input: DC 5V
Signal Type: Differential
Signal Strength (measured at speaker end): ~2V (p to p)
Audio Source: Recorded via on-board microphone over the air.
Max Sound Strength: 57db
WTR050
Input: DC 5V
Signal Type: Differential
Signal Strength (measured at speaker end): ~10V (p to p)
Audio Source: Recorded via on-board microphone over the air.
Max. Sound Strength: 59db
Chinese MP3 Player with PIR Trigger
Input: DC 4.5V (3 AAA Batteries)
Signal Type: Differential
Volume: HIGH
Signal Strength (measured at speaker end): ~7V (p to p)
Audio Source: Pre-recorded then saved to on-board flash using dedicated equipment.
Max. Sound Strength: 83db
Chinese MP3 Player with PIR Trigger
Input: DC 4.5V (3 AAA Batteries)
Signal Type: Differential
Volume: LOW
Signal Strength (measured at speaker end): ~5V (p to p)
Audio Source: Pre-recorded then saved to on-board flash using dedicated equipment.
Max. Sound Strength: 72db
References:
How to make an LM386 audio amplifier circuit
https://www.youtube.com/watch?v=4ObzEft2R_g
BUILD - 386D JRC (LM386) on breadboard (Medium difficulty)
https://www.youtube.com/watch?v=V0H9nW4kPc0
JRC NJM386 Datasheet
https://www.njr.com/semicon/PDF/NJM386_E.pdf
Ti LM386 Datasheet
http://www.ti.com/lit/ds/symlink/lm386.pdf
簡單好用的音頻放大器晶片LM386
http://blog.cavedu.com/2014/10/20/%E7%B0%A1%E5%96%AE%E5%A5%BD%E7%94%A8%E7%9A%84%E9%9F%B3%E9%A0%BB%E6%94%BE%E5%A4%A7%E5%99%A8%E6%99%B6%E7%89%87lm386/
ISD1820 Datasheet
http://www.picaxe.biz/datostienda/descargas/ISD1820.pdf
Single-Ended vs Differential Inputs
https://www.omega.com/techref/das/se-differential.html
DIFFERENTIAL INPUTS
A signal input circuit where SIGNAL LO and SIGNAL HI are electrically floating with respect to ANALOG GROUND. For example, a differential input A/D card will have one HI (+) and one LOW (-) pin for each input. There will also be a LLGND (LOW LEVEL GROUND) pin which may be used if a ground connection is required. This allows the measurement of the voltage difference between two signals tied to the same ground and provides superior common-mode noise rejection. Where should differential inputs be used? Whenever electromagnetic interference (EMI) or radio frequency interference (RFI) is present, a voltage can be induced on BOTH signal wires. A differential input amplifier will reject the COMMON MODE VOLTAGE, provided that the common mode voltage plus the input signal does not exceed the device's CMR specification. The effect on a single-ended input is usually a voltage fluctuation between signal high and signal ground.
SINGLE-ENDED INPUTS
A single-ended input has no commond mode range because there is only ONE low wire, which is shared by all inputs. For example, if you have an A/D board with 16 single-ended inputs, there will be 16 HIGH (+) lines and one LOW (-) line (sometimes called LLGND). Some cards may have several LOW lines to provide extra places to make your ground connection, however, these lines are tied together and are basically the same thing.
WHEN TO USE SINGLE-ENDED OR DIFFERENTIAL INPUTS
Differential inputs provide a more stable reading when EMI or RFI is present, and therefore, it is recommended to use them whenever noise is generally a problem. This is especially true when measuring THERMOCOUPLE, STRAIN GAGE and BRIDGE TYPE PRESSURE SENSOR inputs, since they produce very small signals that are very succeptible to noise.
Single-ended inputs are lower in cost, and provide twice the number of inputs for the same size wiring connector, since they require only one analog HIGH (+) input per channel and one LLGND (-) shared by all inputs. Differential inputs require signal HIGH and LOW inputs for each channel and one common shared LLGND. Single-ended inputs save connector space, cost, and are easier to install.
Single Ended vs Differential Inputs
https://community.plm.automation.siemens.com/t5/Testing-Knowledge-Base/Single-Ended-vs-Differential-Inputs/ta-p/355022
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Checking audio amplifier distortion with oscilloscope spectrum analyzer
https://www.youtube.com/watch?v=n8hNrDcJMCw
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Can a LM386 used with differential inputs?
https://www.diyaudio.com/forums/chip-amps/165934-lm386-differential-inputs.html
The LM386 has an internal amplification set at 20. That means that your differential input will be amplified by 20. So your signal swing has to be below 0,5 volts between the two balanced signals.
Yes it can be done, but keep in mind the chip is not the same as an op-amp. It has internal 50k ohm resistors to ground on the (+) and (-) inputs. The DC bias for both inputs needs to be a few volts below Vcc, closer to gnd. Not sure if you are using a single power supply or dual.
This chip is not very stable and loves to oscillate or pick up RF (AM radio). You might need a small cap 22-100pF across the two inputs, and use the RC output filter too.
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