single supply NE5532 preamplifier circuit

By the people's suggestion I bought myself a breadboard and decided to implement simple (I would even say trivial) single-supply NE5532 chip preamp. Let's see what was done.


Single-supply NE5532 chip preamp made on the breadboard
Single-supply preamp schematic I dropped PSU filters and Zenner diode voltage limiter, since used lab PSU with 15 V voltage.
'Amplifying' resistors are selected to be the same (and thus preamp actually becomes a real one with amplifying ratio equal to 2) and to be equal to the input chain resistance (single supply shift made as resistor-based voltage divider and input resistor) to minimize bias current. That's why there are so many resistors on the actual scheme to match resistance.
Now the results.


Square wave signal Square wave signal has noticeble peaks at the edges, let's see them in details


Square wave signal peak details Given the huge amplitude of the input signal (more than a volt) this may be not a limiting factor actually.
What is a real problem, is the input signal range as a whole. Since I used 15V as a supply voltage, its inner ground will be roughly at 7.5 V (there is an appropriate voltage divider attached to the non-inverting input signal), so having total output amplitude of 4 V may be not appropriate for the chip operational amplifier.


Big sine signal cut Experiments showed that this chip preamp operates correctly when resulted output signal does not exceed 1/10 of the supply voltage (i.e. about 1.2 V max). Triangle and sine signals after some level (when input signal amplitude is about 3-4 V) start producing reversed output signal in the cut area above, i.e. in the middle of the cut line small sine or triangle signal starts growing.
Now question, why do we need chip preamp for the chip amplifier? I believe that the main reason for preamp is to allow to connect power amplifier which may have not very high input resistance, so small preamp with good characteristics (like huge input resistance and very small output one) will not distort small enough input signal. But I think that most of the modern chip sound amplifiers like LM3886 already have big enough input resistance (as all others they have differential amplifier as the first cascade), maybe not that high if would be built with field-effect transistors, but I wonder if that is ever noticeble.
http://www.ioremap.net/node/141

DIY HiVi Research Swans M1 Speakers We got an email from Daniel Bolduc (Quebec, Canada) letting us know that he has followed up his DIY Swans Tempus

We got an email from Daniel Bolduc (Quebec, Canada) letting us know that he has followed up his DIY Swans Tempus Bookshelf Speakers with another DIY build of a HiVi Research speaker. Daniel tells us that the speakers were built for his uncle who was very impressed with the Tempus speakers, but wanted something a little smaller and finished in a piano black high gloss finish.

Sticking with drivers from HiVi, Daniel proposed to build a DIY version of the Swans M1 Speakers. For the enclosure Daniel used a pair of ready made speaker enclosure from Parts Express. I used a pair of the curved Dayton Audio 0.38 ft^3 enclosures with black piano gloss finish for my Fostex FX120 bookshelf speakers and the enclosures are well built and look great.

The high gloss finish on the speaker cabinets will scratch easily so be sure to cover the area well so you don't scratch it with the router when cutting the port and driver holes. The crossover schematic is shown below and Daniel wound his own inductors for the crossover.

The drivers used in Swans M1 speakers are the HiVi F5 (5" bass / midrange) and the HiVi RT1C planer tweeter.

The speaker project cost about $550CDN for the pair and Daniel estimates he invested about 55 hours. I think Daniels build looks much better than the original Swans M1 speakers.

Daniel writes: "So far, I'm very satisfied with the M1's and my uncle is rediscovering his discography with the pair I built for him and is also impressed by the sound reproduction quality."

For full details, more photographs and a materials list for this DIY speaker project, see Daniel's Swans M1 speaker build.

Latest Digital Thermometer DIY project

This diy digital thermometer circuit can measure temperatures up to 150°C with an accuracy of ±1°C. The temperature is read on a 1V full scale-deflection (FSD) moving-coil voltmeter or digital voltmeter.
How the digital thermometer works

Operational amplifier IC 741 (IC3) provides a constant flow of current through the base-emitter junction of npn transistor BC108 (T1). The voltage across the base-emitter junction of the transistor is proportional to its temperature. The transistor used this way makes a low-cost sensor. You can use silicon diode instead of transistor.

The small variation in voltage across the base-emitter junction is amplified by second operational amplifier (IC4), before the temperature is displayed on the meter. Preset VR1 is used to set the zero-reading on the meter and preset VR2 is used to set the range of temperature measurement.

Operational amplifiers IC3 and IC4 operate off regulated ±5V power supply, which is derived from 3-terminal positive voltage regulator IC 7805 (IC1) and negative low-dropout regulator IC 7660 (IC2). The entire circuit works off a 9V battery.

Assemble the circuit on a general-purpose PCB and enclose in a small plastic box. Calibrate the thermometer using presets VR1 and VR2. After calibration, keep the box in the vicinity of the object whose temperature is
to be measured.

Sent by Mihail Dorutz, CH. Thanks a lot!

Digital Thermometer Circuit Schematic

Circuit Bent Keychain Used to Make Easy Dub Siren Overview and explanation

Overview

Illustrated in this simple project is the creation of an Easy Dub Siren from a Circuit Bent Keychain along with a bunch of components.

Explanation

The parts that would be needed to build the Easy Dub Siren include the 8-sound keychain, rotary switch for sound selector and 1MOhm Linear Potentiometer for controlling the pitch of the sound being played back. From the 2 momentary push button switches, one button will be used as a Mute by sending positive output from the instrument jack to the ground and the other will connect the ground to the rotary switch. Other components are solid core wire, rubber feet, 2 knobs, Rasta graphics for front panel, output jack, plastic enclosure, and AA/AAA battery holder.

The output jack is soldered to where the speaker was connected on the sound board and the battery compartment is connected to the 8-sound keychain board. The 1MOhm potentiometer replaces the pitch resistor and the 8 wires are connected to the button connection traces. Holes are drilled in the plastic box for the controls. If space is available inside, push buttons, potentiometer, and rotary switch are mounted in the case.

readmore at:www.circuit-projects.com

Music Stand with Multimode Feature Overview and Explanation

Overview

Four Theremin-type electric field sensors are incorporated by this Multimodal Music Stand (MMMS) along with a microphone and a video camera as input sources for the performance of computer music and electro-acoustic compositions.

Explanation

Using computer vision techniques like tracking the position of an instrument, the device was designed for interactive music performances, audio analysis and transformation of the performers playing. The device performs capacitive sensing through the four electric field sensors which tracks bodily gestures and movements to enhance expressivity. Without modifying the instrument or tether themselves with wires, the MMMS provides the performer added dimensions of musical control in order to influence the interactive aspects of a composition.

Accomplishing the interface to the computer is done by detecting timing signals using custom firmware for the CUI as well as sending the four proximity values to the host as continuous ranges of 16 bits each at an update rate of 100Hz. A full 3-dimensional input is being provided by the MMMS using 4 channels of capacitive sensing. The Z-axis gestural input is determined by the collective E-fields of all four antennas. The different sensing modalities are reinforced in this way to one another.

DIY Data Glove Interface Known as HandUSB Overview And Explanation

Overview

The project can be considered as futuristic as a data glove which can be connected through USB instead of RS232 in order to become an alternative controller for the Pinch Glove fingertip contact glove.

Explanation

A very small SubD adapter housing is used to fit this device as it supports USB standby and consumes low power with 20mA maximum. The device is much faster in responsiveness than the GL-8001 and may later support a USB remote wakeup feature. The project is the reconstruction of a Fakespace GL-8001 device with fully compatible serial interface through USB. The crystal and capacitors can be omitted using the updated V-USB driver. In place of single resistors and multi-diodes, resistor arrays were employed so that it will be easier to populate in case.

V-USB is the basis of writing the firmware where a serial port occurs ready for communication fully compatible to the original GL-8001 box when plugging this device. The baud rate setting is not critical as for V-USB-CDC projects while Windows and Linux have built-in drivers.

A representation of hand interaction is possibly used by Pinch gloves in order to productively work within 3D computer simulation.

DIY Building a Track-Following Robot overview and explanation

Overview

A robot that is capable of following a track at a maximum speed is created in this project wherein the brain of the robot is comprised by an Atmel AT90S4433.

Explanation

There are 2 light-sensitive resistors used in the robot to detect the path as well as the dead ends and junctions. The maximum maneuverability is done without much effort by the two engines that drive the two main wheels. This prototype has been created in order to surpass its original achievement of reaching the highest speed of 8cm/s in a robot contest.

A 10-bit A/D converter that has a 6:1 demux is being featured by the Atmel AT90S4433 which allows sampling up to 6 analog channels one at a time. Both light sensors are currently the only two analog sources that are being read. Since two PWMs are needed to control both engines, the built-in PWM generator could not be utilized in this case. A software for PWM is written with 2 channels using its programmable timer interrupts.

The rubber band transmission can cause the jerky movement seen in the movement which cannot be compensated with the error-time function used to calculate the reaction.