Electronics-Lab.com Blog

Bruce Heran writes:

This is a project that I made to take care of an ever increasing need to prototype vacuum tube (valve) circuits. As you can see from the photos, it really is a test “board”. I do a lot of work with tubes and love to design and improve circuits. In the process I often use various CAD type programs to rough out the designs.

DIY vacuum tube prototyping board - [Link]

Sebastian built an experimental record/looper circuit, resulting in some interesting sample contortionism. [via]

This circuit currently has a few ways to manipulate audio. These are:

A record button allows the user to sample incoming audio to a RAM buffer

A potentiometer sets the input level

A potentiometer sets the sample rate / pitch for playback. The changing of sample rate can be recorded if desired, by physically changing the position of the pot during recording.

The address lines A0 – A18 can be manipulated ie. moved around, removed, replaced, giving a wide range of effects such as stuttering, repeating and basic granulation.
Although this does not sound like heaps of manipulation, keep in mind that this circuit can absolutely mangle a sound beyond recognition. The ADC is running at its maximum speed, and as such the sample rate can be varied greatly for example.

Audio looping & manipulation in RAM - [Link]

Bruce Heran writes:

This project is related to the other tube amplifier projects I have posted. It has more than a casual similarity to the first Push-Pull EL84 (6BQ5) Oddwatt project from nearly two years ago. Both tube amplifier projects use EL84 / 6BQ5 tubes and the earlier one used a ECC802S driver while this one uses 5751 driver tubes. The basic circuits are rather similar, but the new project has a number of differences. Most notably it is easier and less costly to build.

5751 SRPP / EL84 (6BQ5) Push-Pull Tube Amp - [Link]

Mark Houston writes:

Oatley Electronics in New South Wales Australia makes a few kits based around the Raytheon JAN6418 sub-miniature valve (tube). I decided to try out the K272 Stereo Tube Preamplifier – Headphone Driver kit which cost $27AU (~$23US – August 2009). A photograph of the Oatley Electronics tube preamplifier kit is shown below. The kit is complete but comes with very ordinary (generic) components which is not surprising considering the very low cost of the kit. The printed circuit board (PCB) is plated through, dual layered, solder masked and screen printed. The kit can be run off a 9V battery which makes this a safe and ideal kit for those who are new to electronics.

JAN6418 Valve (Tube) Preamplifier / Headphone Amp Kit - [Link]

Audium Semiconductor has launched an audio power amplifier IC which, at normal listening levels, is 20 times more efficient than competing devices, such as Class D amplifiers, without compromising audio quality. The AS1001 operates from a nominal 1.5 V power supply and delivers 100 W peak power output. The amplifier is so efficient that battery-powered amplified loudspeakers can run for up to 10 months on a set of four ‘C’ batteries, playing for three hours per day.

AS1001 chip outputs 100 watts of audio from 1.5 volts - [Link]

A simple Hi-Fi amplifier which is built using a single TDA2050 chip. The circuit is very simple and can easily be constructed on a perfboard or point-to-point so it makes for a good first DIY Audio Project. The power output is about 25W into 8 ohms. The performance of the amplifier is very good (see datasheet) and the fidelity is also very good – comparable or better than most Hi-Fi Class-AB amps which often cost much more.

DIY TDA2050 Hi-Fi Chip Amplifier - [Link]

An optocoupler volume control! What makes this one neat is that optocouplers are used in the circuit. The optocoupler consists of an LED and Light Dependent Resistor (photocell) in a sealed unit. So by varying the intensity of the LED, you can adjust volume. Also, the volume control has no “contact points” in the signal path. So forget about those scratchy potentiometers and get rid of the contact cleaner. The project as shown is 2 channels, but one could easily scale this one up to control multiple channels which could be useful for a DIY home theater.

DIY Lightspeed Passive Attenuator - [Link]

Ever wanted to build a highly dangerous, inefficient, yet awesomely retro piece of electronics? Well, I have. That’s pretty much what a tube amp is. Vacuum tubes are old electronic components that act like transistors, controlling a lot of current with a little current. You usually hear about tubes being used in guitar amplifiers, because they distort in a way that suits guitar playing. However, tubes can also be used to amplify a stereo signal from another audio source such as a CD or MP3 player. Tube amps, unfortunately, aren’t the most practical things in the world; they consume a great deal of power, get very hot, and are big. That being said, they look damn cool, and some people seem to think they sound pretty nice too.  Kit is also available.

Building A Stereo Tube Amp - [Link]

Theremin Style Instrument: This battery powered electronic musical instrument is a descendant of the theremin and can be played without contact from the musician. This easily – assembled, small instrument contains two infared (IR) sensors, one controlling the note, with the other controlling the octave that is played through the speaker in the front. There are seven possible notes (c-b) and 7 possible octaves of each note. The tone is reflected by one of seven colors that illuminates the center area and highlights a small indicator located on the top panel. The brain of this piece is a boot-loaded atmega chip. The source code is available, as well as, pictures and a video. Check it out here:

Squaremin – Theremin Style Instrument - [Link]

This tube amplifier is constructed uses point-to-point connections and the majority of the parts have been salvaged from old electronics. The amplifier uses 6T9 compactron vacuum tubes in a push-pull output stage. The preamp section uses 12AX7A tubes.

DIY 6T9 Push-Pull Tube Amplifier Project - [Link]