Amplifiers

I spent much of 1997 designing and building my ultimate dream amplifier, which I named "The Emperor's New Amplifier"TM (TENA) for a quality it shares with the fabled emperor's wardrobe-- transparency. It was also an oblique reference to the marketing hype that pollutes high-end audio. I thought about commercializing it, especially when the lab where I worked announced it was shutting down, but I soon realized that marketing high-end tube amplifiers is not a reliable way to make a living. (I'm paycheck-addicted.) Counterpoint Electronics, a high-end audio manufacturer located in a 45,000 square foot building five miles from where I lived at the time, vanished overnight. Then I thought I might write a magazine article, but the move to Colorado distracted me.

Chu Moy designed a very popular headphone amplifier that's easy to build, and it can be built small enough to fit in a pocket, power supply and all. It's powerful enough to drive very inefficient headphones to thunderous volumes from even weak sources, and it sounds excellent considering that you can build a bare-bones CMoy amp for just US$20, and a pretty nice amp for under $50.

Several people have requested that I set up a web page with construction details for the second of two power amplifiers that I published in Audio magazine. This amplifier is the monophonic 270 watt Double barreled Amplifier. For the original article, I specified plus and minus 85 V dc power supply voltages. The voltage can be increased to about 93 V to obtain a power rating of 300 W.

The simplified circuit [Fig.2] shows that each sub-amplifier consists of two voltage gain stages. The first stage consists of a complementary two stage common emitter [Q1-7] whose gain is about x2.3. The second stage is a current mirror stage [Q13-14] which drives the voltage across a load resistor tied to 0V.

This simple audio power amplifier was originally designed for a circuit board workshop, conducted by the OSU IEEE Student Group. At the workshop, 20 participants each constructed this amplifier, by etching and drilling the single sided circuit board, soldering all components, and attaching a pre-built heatsink assembly with the output transistors. Three workshops were held between 1995 to 1996.

A medium power amplifier that is characterized by a lot of good sound quality, but simultaneously is very simple in the construction. Him uses, enough time in my active loudspeakers. In his output stage exist the very good FET transistors, technology HEXFET, transistor which are controlled by voltage and no by current as the classically bipolar transistors.

An amplifier to drive low to medium impedance headphones built using discrete components. Both halves of the circuit are identical. Both inputs have a dc path to ground via the input 47k control which should be a dual log type potentiometer. The balance control is a single 47k linear potentiometer, which at center adjustment prevents even attenuation to both left and right input signals.

Because of their sound, Trainwreck amplifiers (http://www.trainwreck.com) have an almost occult like following among guitarists. And, because they are produced in such small volumes, they are almost impossible to obtain. If you're lucky, you may find one on eBay for $20,000 or more.

Audio-taper pot, R1, adjusts input level into two LM386 amplifier chips. The LM386 is a low-voltage audio power amplifier, designed to operate on 4V to 12V. It has an internal 15K feedback resistor between pins 1 and 5 which would set the gain at 20 (26dB).

The amp gives about 0.5W into 32 ohms. In the classical definition of class A, the top transistors would be sourcing 120mA and the bottom transistors sinking 0mA. However the two 3k resistors in the second stage actually prevent the total shutdown of either transistor bank by keeping the opposing stage at an absolute minimum of 5mA. In any case, 0.5W into Grados is unbelieveably loud.

You can use this powerfull amplifier in any small audio project. It is very small (6.5 x 4.5 cm).It outputs 10W and uses a 9V battery.

High Quality, very simple design. No preamplifier required. This design is based on the 18 Watt Audio Amplifier, and was developed mainly to satisfy the requests of correspondents unable to locate the TLE2141C chip. It uses the widespread NE5532 Dual IC but, obviously, its power output will be comprised in the 9.5 - 11.5W range, as the supply rails cannot exceed ±18V.

Useful to listen in faint sounds. 1.5V Battery operation. This circuit, connected to 32 Ohm impedance mini-earphones, can detect very remote sounds. Useful for theatre, cinema and lecture goers: every word will be clearly heard. You can also listen to your television set at a very low volume, avoiding to bother relatives and neighbors. Even if you have a faultless hearing, you may discover unexpected sounds using this device: a remote bird twittering will seem very close to you.

This is an image Schematic. No Description available.

This is an image Schematic. No Description available.

The LM12 is a power op amp capable of driving ±25V at ±10A while operating from ±30V supplies. The monolithic IC can deliver 80W of sine wave power into a 4 load with 0.01% distortion. Power bandwidth is 60 kHz. Further, a peak dissipation capability of 800W allows it to handle reactive loads such as transducers, actuators or small motors without derating.

Here is the schematic for an 8 watt audio amp. This amp can be used as a simple booster, the heart of a more complicated amplifier or used as a guitar amp. The circuit can be built on a perf board, universal solder board or PC board, the PC board is preferred. I built the circuit on a perf board and had to add extra inductors, capacitors and resistors to prevent oscillation.

An eight watt amplifier based on the LM383 power audio amplifier ic. It's advised that you use this ic with a suitable heatsink.

Description is not in English language.

This solid-state push-pull single-ended Class A circuit is capable of providing a sound comparable to those valve amplifiers, delivering more output power (6.9W measured across a 8 Ohm loudspeaker cabinet load), less THD, higher input sensitivity and better linearity.