Musical Circuits

The circuit of the unit is fairly simple, but is a bit irksome to set up. The reason is that obtaining matched FETs is not easy, so I had to make sure that the circuit would work with off-the-shelf FETs. The phase shifter is a standard opamp circuit, and has been used for this sort of application many times. After experimenting with alternative variable resistors, I decided that the FET was still the best choice, although they are fairly critical to set up, and have linearity problems.

This simple voltage divider will allow you to record that sweet sound you can only get on your {fill in you favorite amp, here}, without having to use a microphone: Get your rig sounding the way you like it and then connect this across your speaker terminals; your amp won't even know it's there. Feed the output into a mixing board, or bus it into the monitor channel(s) so the horn section can hear your solos, too.

The circuit in Figure 1 produces timing signals with a sound like that of a mechanical metronome. IC1 is a 555 timer that oscillates at approximately 3200 Hz. The two 3-kW resistors and the 0.047-µF capacitor set the frequency. IC2 divides the frequency of IC1's output by 2. IC2 produces a square wave with an exact 50% duty cycle. The frequency of the output of IC2 determines the sound of each beat. A higher frequency yields a sharper sound, like beating on a small drum; a lower frequency produces a deeper sound, like beating on a large drum.

This circuit was designed to obtain a valve-like distorted sound from an electric guitar or other musical instrument. For this purpose a very high gain, three-FET amplifier circuit, was used. The output square wave shows marked rounded corners, typical of valve-circuits when driven into saturation.

These two projects , Wah and Fuzz, are the results of a modification to a Morley dual channel volume control pedal that one of my sons suggested I undertake as He had no use for the volume unit but thought I could modify the pedal into a Wah unit. I decided later to add a Fuzz circuit and combine the two into a single switchable unit as described further on. Not being one to re-invent the wheel, I downloaded several circuits from the Internet and after breadboarding severals I chose the original Morley circuit as it had the best sound and was using an LDR/LED control which simplified its construction.

This design adopts a well established circuit topology for the power amplifier, using a single-rail supply of about 60V and capacitor-coupling for the speaker(s). The advantages for a guitar amplifier are the very simple circuitry, even for comparatively high power outputs, and a certain built-in degree of loudspeaker protection, due to capacitor C8, preventing the voltage supply to be conveyed into loudspeakers in case of output transistors' failure.

This is simple but elegant design, that provides excellent tonal range. The gain structure is designed to provide a huge amount of gain, which is ideal for those guitarists who like to get that fully distorted "fat" sound. However, with a couple of simple changes, the preamp can be tamed to suit just about any style of playing. Likewise, the tone controls as shown have sufficient range to cover almost anything from an electrified violin to a bass guitar - The response can be limited if you wish (by experimenting with the tone control capacitor values), but I suggest that you try it "as is" before making any changes.

The bass lift curve can reach a maximum of +16.4dB @ 50Hz. In any case, even when the bass control is rotated fully counterclockwise, the amplifier frequency response shows a gentle raising curve: +0.8dB @ 400Hz, +4.7dB @ 100Hz and +6dB @ 50Hz (referred to 1KHz). As amplifiers of this kind are frequently used to drive small loudspeaker cabinets, the bass frequency range is rather sacrificed. Therefore a bass-boost control was inserted in the feedback loop of the amplifier, in order to overcome this problem without quality losses.

Barebones. Use this configuration with two pickups, for a lead/rhythm switching effect. Tone pot is linear taper; volume pot is audio taper. Use a high-quality, "Orange Drop" capacitor and top it off with a "Switchcraft" 1/4' phone jack.

The circuit is a simple, but accurate Digital Guitar Tuner. It samples the input, which can be directly from the mics of an electric guitar, or from a microphone, it you're using an acoustic guitar. It can ofcourse also be used for tuning other instruments. The samples are then checked against stored values for the strings, and the two LED's will show the tuning status - "Too Low", "Too High" or "In Tune" when both LED's are lit. The tuner will automatically switch between the six strings. The circuit is pretty simple. A small transistor amp pumps up the input signal to something the AVR can see on it's input pin. The other two I/O pins are used for driving the LED's.

This amplifier is not trivial, despite its small size and apparent simplicity. The total DC is over 110V (or as much as 140V DC!), and can kill you. The power dissipated is such that great care is needed with transistor mounting. The single board P68 is capable of full power duty into 4 Ohm loads, but only at the lower supply voltage. For operation at the higher supply voltage, you must use the dual board version. There is NO SHORT CIRCUIT PROTECTION. The amp is designed to be used within a subwoofer or other speaker enclosure, so this has not been included. A short on the output will destroy the amplifier.

This circuit was inspired by a friend who wanted a reberb for his portable guitar amplifier. I originally tried using NE5532 low noise op-amps for the buffer stages but they were too noisy for the low level circuits so I switched to discrete 2N3904 transistors, they seem to be fairly quiet. This circuit has a nice feature not found in most reverbs, a drive control for the spring amp. The drive can be turned way up and a nice smooth distortion effect will come out of the spring. The circuit will run on a 9V battery but will probably run it down fairly quickly, it draws about 30ma idle and around 100ma with a full signal going through.

Observing my "Boss" pedals and how they were switched on and off I figured there must be more to it. It took me only about 4 hours to design and test this circuit, It works very well and I'm really satisfied with it so I'll be using it in all the effect pedals I build. It's a very clean bypass both electronically and mechanically.

This page describes how to build this full-bandwidth single-port (one input and one output) MIDI interface. The interface is buffered (that is, if the PC gets behind you won't lose data) and it works in Windows 3.1 and Windows 95 using a special (and very well-behaved) device driver. A simpler version, using an Atmel AT89C2051 microprocessor, is described here.

The unpretentious controller in Fig 1 remembers the interval between your pressing its start and stop buttons. Thereafter, the controller switches the load on and off every day at the same times as you did. You reset the controller by pressing the buttons to enter settings.

Well, here's what you've all been waiting for. Sorry bout the delays. Anyway, I don't have a scanner, so I typed this in last night (at 1am, hopefully I copied it right). If it's unreadable you might want to check the source directly, the book's at the bottom. I hope I'm not violating any laws by posting this.

Simplified Analog Input Schematic This schematic represents the input circuitry for a single input. This circuit is a track and hold. The idea is that the input waveform may reach a peak at any instant as the drummer strikes the pad. When that occurs, the capacitor is charged to the peak input voltage. There is only one A/D converter (ADC0804, see the Main CPU section schematic), and it takes time for it to convert an input voltage to a 8-bit code. No matter when the drummer strikes the pad, the capacitor will "remember" the peak input voltage, so that it can be read later as the A/D convert cycles through the 8 inputs. This plot shows the track and hold cirucit in action. The lower waveform is the raw input from the pad's transducer, and the upper waveform is the output which will be read by the A/D converter at some later time.

The complete circuit, loudspeaker, batteries, input and output jacks can be encased in a small box having the dimensions of a packet of cigarettes, or it could be fitted also into a real packet of cigarettes like some ready-made units available on the market.

This is a computer I built for my car, it’s an MP3 music system but can also do other tasks. Based around a super-small “sub-micro ATX” motherboard from a computer known as the BookPC BKi810, I have put the motherboard, hard drive, and a 12 volt power supply in a small case that fits under the seat of my car. Total size is approximately 11 x 8 x 2 inches. The motherboard has a lot built in. The connectors, from left to right, are mouse, keyboard, 100 MB ethernet, 2x USB, printer, S-Video, composite video, VGA video, joystick/MIDI, audio out, line in, mic in, and then two connectors I added: power in and remote control.

The aim of this design was to reproduce a Combo amplifier of the type very common in the 'sixties and the 'seventies of the past century. It is well suited as a guitar amplifier but it will do a good job with any kind of electronic musical instrument or microphone. 5W power output was a common feature of these widespread devices due to the general adoption of a class A single-tube output stage (see the Vox AC-4 model). Furthermore, nowadays we can do without the old-fashioned Vib-Trem feature frequently included in those designs.