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]
Here’s a cool Mini LED volume towers project by Ben Finio. He writes a complete step-by-step instructions here:
The inspiration for this project started when I saw a variety of awesome stereo LED towers on YouTube (also referred to as VU meters). Many of the videos showed the end result, and maybe a slideshow of the assembly process, but lacked complete build details or a circuit diagram. So, I set out to find out how they worked, and build my own “mini” desktop version that would go nicely with computer speakers, instead of a big living room stereo. This Instructable will give you complete directions to assemble the required circuit (even if you have no electronics experience – you can even do it without soldering), build two LED towers, and hook them up to an audio input so you can simultaneously drive them and listen to music.
Mini LED volume towers (VU meters) - [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]
w2aew @ youtube.com writes:
This video presents a simple automatic audio volume leveling circuit. The application that prompted this is a police/fire/emergency scanner. Often times, different services will have different volumes in the receiver – so adjusting for a comfortable listening level on one service/station will often lead to other services being too loud or too quiet. This circuit will automatically adjust the volume of each received signal based on the signal’s peak amplitude. Similar circuits have been widely published, so there’s really nothing new here – just a quick tutorial and demonstration of how this circuit works. An arrangement of capacitors and diodes are used to implement a peak detector to measure the input signal amplitude. The dynamic impedance of diodes is controlled/changed to adjust the signal level. The result is a leveling circuit that has a very wide input dynamic range with a near constant average output level.
Circuit fun: Automatic audio leveling circuit - [Link]
This project is a message recording board capable of recording 10 to 20 secs depending on audio quality.
This project has been designed around Winbonds ISD1616 IC (SMD) IC, which is fully integrated, single-chip, single message voice record and playback device ideally suited to a variety of electronics systems, Message duration is user selectable in ranges from 10 to 20 Seconds depending on the sampling rates from 4 KHz to 12 KHz adjustable via preset, giving the users greater flexibility in duration versus recording quality.
20 Seconds Voice Record – Playback board - [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]
xristost has written an article about his latest project LED VU meter with LM3916:
This was finished months ago and just now I had time to finish the article. LM3916 is a dedicated IC for VU LED meter. Unlike LM3915 which have 3dB step between voltage levels, the LM3916 have nonlinear steps: -20, -10, -7, -5, -3, -1, 0, +1, +2, +3db, just like old school analog VU meters. I saw in YouTube an interesting commercial LED VU meter, which imitates the needle movement in analog VU meters and I thought I can make a similar one. All I needed I found in the datasheet of LM3916. The LM3916 can be feed with AC signal without any rectification, but I wanted to implement a precision full wave rectification.
LED VU Meter with LM3916 - [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]
Here’s something I’ve been working on for a while. It’s a digital guitar effects processor based on a PIC32MX.
It started with a conversation with my brother John. We were playing with my mini drum-machine, using the tune mode to mash the hell out of the samples whilst running it though his bass guitar amp with some heavy feedback. It sounded pretty cool, very NIN and got us onto the idea of making a digital effects pedal using the same microprocessor. The PIC32MX is a pretty capable device running at up to 50Mhz with loads of built-in peripherals including a 10bit ADC. Definitely possible I thought.
ChipStomp – A Digital effects pedal built with a ChipKit DP32 - [Link]