by Sagar Savant:
Measuring performance of audio components like microphones, speakers, converters, and amplifiers can be a difficult task. In this post, I’ll talk about some of the tools I use to make this job easier. Analyzers, reference transducers, calibrators, meters, and more come with various feature sets and price tags. The items below just happen to be my favorites.
Soundcheck (Listen Inc.): Soundcheck is a versatile audio analyzer that I’ve used for years in both R&D and production line environments. It’s built in a “modular” way, so you buy the features that you need. What I love about this software is the customization potential in everything from the granularity of frequency points in a sine sweep to the ability to post process measurements in a sequence automatically based on macros. Soundcheck is not cheap, but it saves me tons of time when I need to measure and report on audio components or subsystems.
GPiO Audio Measurement Toolbox – [Link]
by Matt Renaud:
What really drove me to build this 6EM7 amp was an idea about amplifier layout. Looking back at most of my tube designs, and most of those on the internet, revealed a very typical pattern. Amplifiers tended to be flat chassis with tubes and transformers above and electronics below. From a historical perspective this makes perfect sense. Metal chassis were built this way to facilitate packaging and assembly. When people started to make tube amplifiers again, they just removed the upper case and built in the same way.
6EM7 Single-Ended Triode (SET) Vertical Amplifier – [Link]
The dual low power amplifier built around TDA2822 8pin DIP. IC, it is mainly designed to use in portable players, radios and other building block project. A 3V supply can be used to drive headphones providing 20mW in 32 Ohms per channel, and a 12V power supply will provide 1W in 8 Ohm per channel for small loudspeakers.
Mini Stereo Audio Amplifier – [Link]
The 6.5W Stereo Audio Amplifier project built around TDA2004 IC. The TDA2004 is a class B dual audio power amplifier, specifically designed for car radio applications etc.
6.5W Stereo Audio Amplifier – [Link]
The project built around Philips TDA1521 IC, The project provides high quality audio 2X10W Audio output. The device is especially designed for mains fed applications, (e.g. Stereo TV Sound and Stereo Radio). The circuit designed for asymmetrical power supply systems.
10W Stereo Audio Amplifier – [Link]
This is a small 2 Channel amplifier constructed around Sanyos LA4445 IC delivers 5.5Watts +5.5 Watts at 4 ohm load, supply in 12V DC 2Amp, Input impedance 30K.
Dual Channels output : 5.5W
Minimum External Parts
Very small pop noise at the time of power supply ON/OFF
Good ripple rejections
Small residual noise
Built-in protectors 1. Thermal Protector 2. Overvoltage Surge Protector
Standard Audio signal
Supply 12V DC
Load : 4 Ohms Speaker on Each Channel
Voltage Gain : 50DB
Output 5.5W on each Channel (THD 10%)
Total harmonic distortion 1% Max @ Po=1W
Input impedance 30 K-ohms
5.5W – 2 Channel Audio Amplifier – [Link]
20W Bridge Audio Amplifier project, based on the TDA2005 IC, The TDA 2005 IC is class B dual audio amplifier, specifically designed for car radio applications etc.
Power supply input : 18 VDC
Output power : 20 W, 4 Ω
IC built in Thermal Shut-down, Load dump voltage surge protected
Terminal pins for connecting left and right audio signal inputs
Berg Connector for connecting Potentiometer (POT) for volume adjustment
Power Battery Terminal (PBT) for easy power supply and speaker connection
Power-On LED indicator
Heatsink for IC
Four mounting holes of 3.2 mm each with nut and stud
PCB dimensions 63 mm x 65 mm
Note : Use shielded cable for connecting potentiometer
20W Bridge Audio Amplifier – [Link]
14W Stereo audio power amplifier build around LM4730 IC. The LM4730 is stereo audio amplifier capable of delivering typical 14W per channel of continues average output power a 4 Ohms or 8 Ohms load with less than 10% THD+N from 20Hz to 20Khz frequency. Each amplifier has an independent smooth transition fade-in/out mute and a power conserving standby mode which can be controlled by onboard slide switches.
The LM4730 has short circuit protection and thermal shutdown feature that is activated when the IC temperature exceeds 150 centigrade. The LM4730 also has under voltage lock out feature for click and pop free power off and on. Amplifier required proper heat sink.
14W Stereo Audio Amplifier – [Link]
Project has been designed to record & playback multi voice massages using Winbonds ISD1740 IC. Messages are stored in flash memories made in unique Multilevel Storage Technology (MLS). Circuit provides high quality audio recording and simple operations. Circuit operates in dual mode standalone or micro-controller SPI mode. Onboard tactile switches for standalone mode and 10 (2×5) pin box header connector for SPI mode. 26 to 80 Seconds voice massage recording capacity.
– Supply 2.4 to 5 VDC (5 VDC @ 100 mA)
– 26 to 80 Seconds selectable voice recording capacity
– Selectable sampling rates 11.5 KHz, 7.8 KHz, 6.4 KHz, 5.3 KHz, 4.5 KHz
– Directly drive 8 Ohms speaker or typical buzzer
– Analog audio out to driver external audio amplifier
– Digital volume control via onboard tactile switch
– Dual mode operation stand alone or micro-controller
– SPI Interface (4 wire serial interface)
– 10 (2×5) Pin box header for SPI interface
– Full control on memory and analog path configuration audio input, output and mix in SPI mode
– Automatic power-down after each operations cycle (standalone mode)
– Onboard tactile switch for Record, Play, Erase, FWD, Volume control, Reset and Feed-Through
– Onboard power indication, record play indication
– Voice message fed in via microphone or analog signal in
– ISD1740 provides a PWM class D speaker driver and speaker output simultaneously –
– 100 Years message retention
– 100,000 Record cycles
– Four mounting holes of 3.2 mm each
– PCB dimensions 80 mm x 76 mm
20 to 80 Seconds Voice Record Playback with SPI control – [Link]
The Mini Audio Amplifier project is a good choice for battery operated gadgets. It is based on Texas instruments LM386 IC, provides high quality Audio.
– Wide power supply input 6 to 12 VDC
– 500 mW output @ 8 Ohms load
– Takes standard audio signal as input
– Low quiescent current drain 4 mA IC
– The quiescent power drain is only 24 mW when operating from 6 VDC
– Onboard preset for volume adjust
– Header connector for connecting power supply, audio signal and speaker
– Onboard power indication LED
– On/Off PCB mounted slide switch for power supply
– Four mounting holes of 3.2 mm each
– PCB dimensions 41 mm x 41 mm
Mini Audio Amplifier – [Link]