by Giovanni Militano @ diyaudioprojects.com:
I’ve always enjoyed electronic kits of all kind and like many of you will credit them for the foray into DIY audio. Over time as my DIY skills matured I found myself taking the DIY route for projects far more often than relying on kits. While I will always enjoy electronic kits, I generally won’t try one out unless there is something really unique about the kit. When I saw the Gobo Stereo Audio Amplifier kit from boxedkitamps.com, I was immediately intrigued by the unique looking enclosures available with the amplifier kits. Shown in Photograph 1 below is the completed Gobo Stereo Audio Amplifier kit with a translucent blue acrylic enclosure. The choice of enclosure finishes for the Gobo stereo amplifier kit include blue, dark grey and orange acrylic and bamboo.
Gobo Stereo Audio Amplifier Kit (LM1875, 15W, Class-AB) - [Link]
The amplifier is based on the 12AU7 valve (part number ECC82 in Europe). The schematic came from here, it’s a nice kit, but lacked a power supply and the layout wasn’t quite what we needed for kits in TinkerSoc. I added a LDO 12v regulated power supply, an input volume control pot and kept the design single layered (with one jump). The final schematic can be viewed here
Tube Amplifier - [Link]
The CMoy headphone amp is a popular headphone amplifier that is small enough to carry everyday and powerful enough to drive headphones at higher levels than normal. Most headphones and most sources will get along ok, but there are players with weak output, and high end headphones typically give up efficiency for the best sound.
The CMoy amp was originally designed by Chu Moy, and at this point there are hundreds of variations with different components, layout, and features. Sometimes, users simply swap op-amps for a different sound and performance. This circuit uses op-amps to directly drive headphones, something they are not designed to do, also, some of the op-amps used are not even designed for audio applications!
Here is a simulation of ½ of a CMoy amp. It outputs over 4V from a 0.4V source. It provides decent audio fidelity from just a few small and inexpensive components. In the last few years, CMoy style headphone amplifiers have been very popular with the DIY audio crowd to increase the audio output to some of the larger and higher impedance headphones available.
DIY audio enthusiasts typically stuff these components into an Altoids tin, other tins, or other small project boxes. The CMoy style of amplifier is versatile enough to fit into many different form factors. Users also determine the container based on what features they choose to include with their circuit. They might add features like bass boost, DC input, and rechargeable batteries.
CMoy Headphone Amp - [Link]
Have no fear… even if this project sounds complex, you’ll easily learn in this article many things about high speed electronics and PCBs. In fact, my goal here is to teach you some basics about all the new problems that arise when you’re dealing with GHz signals
Amplifying nanosecond pulses for quantum physics experiments - [Link]
This is my second encounter with LM3886. I was pleased of the sound this chip produced the first time, so I decided to make another amplifier with it. The schematic is based on the schematic in the datasheet of the chip with minor changes.
50W Power Amplifier with LM3886 - [Link]
In this episode Shahriar presents a tutorial on the design and characterization of a single-stage low-noise bipolar amplifier suitable for audio applications. Given a set of specifications, a common-emitter topology is investigated. The circuit employs a beta-insensitive biasing scheme which is simultaneously optimized for maximum output swing. The small-signal gain of the circuit is calculated and the bandwidth is set for audio frequencies. A non-inverting operational amplifier is used as a second stage to achieve the desired overall gain. The circuit is assembled on a breadboard where the gain and bandwidth are measured and compared with design specifications. As the final experiment, the circuit is used to amplify signals from a microphone.
Tutorial on the Theory, Design and Characterization of a Single Transistor Bipolar Amplifier - [Link]
by Roy McCammon:
The traditional three op-amp differential amplifier’s signal to noise ratio can be improved by 6dB by adding a resistor and slightly changing the connections. There is a trade-off though: The traditional topology has a high input impedance, whereas the low-noise version has a lower input impedance.
Differential amp has 6dB lower noise, twice the bandwidth - [Link]
by University of Bristol:
A breakthrough in the design of signal amplifiers for mobile phone masts could deliver a massive 200MW cut in the load on UK power stations, reducing CO2 emissions by around 0.5 million tonnes a year.
Funded by the Engineering and Physical Sciences Research Council (EPSRC), the Universities of Bristol and Cardiff have designed an amplifier that works at 50 per cent efficiency compared with the 30 per cent now typically achieved.
Currently, a 40W transmitter in a phone mast’s base station* requires just over 130W of power to amplify signals and send them wirelessly to people’s mobiles. The new design, however, enables the transmitter to work effectively while using just 80W of power.
New design for mobile phone masts could cut carbon emissions - [Link]
w2aew @ youtube.com writes:
A tutorial on the basics of an inverting and non-inverting summing amplifier using an op amp. The video assumes a basic knowledge of how inverting and non-inverting amplifiers using op amps work. If you are unfamiliar with this, I’d recommend viewing my video on how to easily understand the operation of most opamp circuits: https://www.youtube.com/watch?v=K03Rom3Cs28
Basics of an Op Amp Summing Amplifier - [Link]