Shared Projects by Blueberry

An audio amplifier based on an LM4950 chip. Note that the polarity must be correct with the tantalum capacitor.

This is an implementation of a hearing aid circuit as presented on radiofun232’s YouTube channel.

The goal is an inexpensive, open source, battery powered amplifier that takes a signal from a condenser microphone and drives an earphone to help people who are having trouble hearing. This board is designed to be worn around the neck with an earphone connected to the 3.5mm barrel jack.

Part list:
B1, B2 - AA battery holder - Digikey p/n BCAAPC-ND
M1 - Condenser microphone - Digikey p/n 102-1721-ND
J1 - 3.5mm Barrel jack - Digikey p/n CP1-3523N-ND
LED1 - 5mm Green LED - Digikey p/n 754-1263-ND
S1 - Slide switch - Digikey p/n EG1916-ND
C1 - 0.1uF capacitor - Digikey p/n 399-4329-ND
C2 - 0.22uF capacitor - Digikey p/n 478-4863-ND
C3 - 0.047uF capacitor - Digikey p/n 399-4371-ND
C4 - 47uF capacitor - Digikey p/n 399-6610-ND
Q1 - BC557 pnp transistor - Digikey p/n BC557BTACT-ND
Q2, Q3, Q4 - BC547 npn transistor - Digikey p/n BC547BTACT-ND
Q5 - BC237B npn transistor - Digikey p/n BC237BGOS-ND
R1, R2, R3 - 1k Ohm resistor - Digikey p/n CF14JT1K00CT-ND
R4 - 66.5k Ohm resistor - Digikey p/n 66.5KXBK-ND
R5 - 100 Ohm resistor - Digikey p/n CF14JT100RCT-ND
R6 - 1M Ohm resistor - Digikey p/n CF14JT1M00CT-ND
R7 - 470k Ohm resistor - Digikey p/n CF14JT470KCT-ND
R8 - 220k Ohm resistor - Digikey p/n CF14JT220KCT-ND
R9 - 10k Ohm resistor - Digikey p/n CF14JT10K0CT-ND
R10 - 27 Ohm resistor - Digikey p/n CF14JT27R0CT-ND
R11 - 470 Ohm resistor - Digikey p/n CF14JT470RCT-ND
32 Ohm Headphone - link or equivalent

This circuit has not been tested yet, and it will almost certainly have some tweaks after assembling the board. So stay tuned for the final version. :-)

A breakout board for an ATTiny10. The controller and filter cap are mounted on the bottom, and the pins are labelled on the top.

Just add an ATTiny10, a 0.1uF cap in a 0805 package, and a 6 pin header (0.100" pitch).

This board may be appropriate for other six pin variants of this micro-controller as well.

An approx. 10 Watt mono class D bass guitar amplifier for driving an 8-ohm speaker. The power amp is based on a TPA3125 chip. A 12-volt power supply capable of delivering at least 1 amp (preferably more) is required. Use a decent quality power supply. I found the cheap power supplies to be too noisy.

Cost: approx. $40 per completed board
Board: approx. $42 for (3) boards
Parts: approx. $26 per board

Status: see video here; use at your own risk

Bill of Material:
U1 - Audio Op-amp, p/n: LM833NGOS-ND
U2 - 10V, 100mA Regulator, p/n: 296-1996-ND
U3 - TPA3125 Class D Amplifier, p/n: 296-24090-5-ND

Q1 - MOSFET, n-Channel, 200mA, p/n: 2N7000TACT-ND

L1, L2 - 22uH, 4A Inductor, p/n: AIUR-06-220K-ND

C1, C2, C3, C4, C6, C21, C28 - 10uF, 50V Aluminum Cap, p/n: 493-11003-1-ND
C5 - 100uF, 16V Aluminum Cap, p/n:493-4638-1-ND
C7, C27 - 100pF, 50V Ceramic Cap, p/n:445-4726-ND
C8, C10, C11, C14, C15, C22 - 1uF, 16V Ceramic Cap, p/n:445-8614-ND
C9, C16, C17, C18, C19, C20 - 0.22uF, 50V Ceramic Cap, p/n:445-8625-ND
C12, C13 - 470uF, 35V Aluminum Cap, p/n:P14942-ND
C23, C24 - 1000pF, 50V Ceramic Cap, p/n:445-5246-ND
C25, C26 - 10000pF, 50V Ceramic Cap, p/n:445-4750-ND

R1, R2 - 1Meg, 1/4W Resistor, p/n: 1.00MXBK-ND
R3, R4 - 2.21k, 1/4W Resistor, p/n: 2.21KXBK-ND
R5 - 1k, 1/4W Resistor, p/n:1.00KXBK-ND
R6 - 22.1k, 1/4W Resistor, p/n: 22.1KXBK-ND
R7, R8, R9, R16 - 47.2k, 1/4W Resistor, p/n: 47.5KXBK-ND
R10, R11 - 10k, 1/4W Resistor, p/n: 10.0KXBK-ND
R12 - 10k Potentiometer, p/n: CT6EP103-ND
R13 - 100k Potentiometer, p/n: PTV09A-4225F-B104-ND
R14, R15 - 3.3 Ohm, 1/4W Resistor, p/n: 3.3QBK-ND

J1, J2, J3 - 2 Pos Terminal Blk, p/n: ED1643-ND

Misc:
Knob, p/n: 450-1742-ND
¼" Jack, p/n: SC1316-ND
12V Power Supply, p/n: 285-1884-ND

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