Headphone amplifiers powered by a computer's USB connector. Scheme, description

Free technical library

ENCYCLOPEDIA OF RADIO ELECTRONICS AND ELECTRICAL ENGINEERING
Free library / Schemes of radio-electronic and electrical devices

Headphone amplifiers powered by a computer's USB connector. Encyclopedia of radio electronics and electrical engineering

Free technical library

Encyclopedia of radio electronics and electrical engineering / Transistor power amplifiers

Comments on the article

When working with sound files, the computer sometimes lacks the usual, "non-virtual" analog volume control: for example, if the sound signal level suddenly increased, and on the display screen there is a window of another program that is not related to the sound card. You can, of course, use headphones that have such a regulator or make an adapter with a regulator that connects between the line output of a computer sound card and headphones. However, it is not always possible to find a low-resistance (several tens of ohms) dual variable resistor for such a regulator.

The most suitable way out for me turned out to be an additional headphone amplifier, which can be powered from a free USB jack, they are available in every modern computer. sound card, usually located on the back of the computer. Such a UGT will require a minimum of parts.

One of the diagrams of such a device is shown in Fig. one

USB powered headphone amplifiers
Fig. 1

Each of the UGT channels is an amplification stage on a composite transistor loaded with an L1 choke (12). This allows you to connect headphones to the UGT output avoiding additional oxide capacitors that introduce nonlinear and frequency distortions. They arise due to electrochemical processes occurring in capacitors during their periodic recharge. The voltage gain in such a UGT can be small - 3 ... 5 times it is dictated by the ratio of the resistances of the resistors R2 and R8 (R3 and R9).

At the input of the UGT, a volume control is installed - a dual variable resistor R1. In the process of testing the UGT, it turned out that interference from the digital nodes of the computer penetrates through the closed loop of the common wire. The protective choke-transformer T1 on the ring magnetic circuit helped to cope with such interference (three K10x7x3 rings made of M2000NM ferrite put together). 3-4 turns of a shielded cable are wound around the rings, leading to the line-out connector of the computer's sound card. The ring can be selected with a larger diameter, depending on the thickness of the cable. It is better to place the T1 transformer near the X1 plug; if desired, it can be closed with a decorative cover.

USB powered headphone amplifiers
Fig. 2

The double variable resistor R1 must have a non-linear characteristic of type B. If this is not available, then a double resistor with a linear characteristic (type A) can also be used, but then it is advisable to build the UGT according to the circuit shown in Fig. 2 where the volume control is included in the negative feedback circuit.

In both versions of the UGT, output transformers from old portable radio receivers, for example, from "VEF-1" or similar, can be used as L2 L202 chokes. The primary and secondary windings should be connected in series (according to) In the author's design, two identical transformers from West Electric telephone sets manufactured in the 60s of the last century were used (the total inductance of their windings is about 1 Gn) Similar transformers from Soviet-made telephone sets are probably also suitable , all windings of which are also connected in series. It is necessary to avoid using that part of the primary winding, which is wound with nichrome wire and has a significant active resistance. The active resistance of the inductor winding should not exceed 30 ohms.

Transistors can be KT315B, selected in pairs according to the current transfer coefficient.

The amplifier is mounted on a breadboard printed circuit board.

To turn on the amplifier for the first time, it is desirable to power it from a battery. If the total quiescent current of the transistors in each of the channels is set to 15 ... 20 mA, then adjustment is not required. If this current turns out to be less, then it is necessary to select resistors R4 R5 (R6, R7 for the circuit in Fig. 2).

On 32 ohm headphones, the amplifier delivers up to 80 mW of power. The author did not measure the level of non-linear distortions introduced by the UGT, but by ear the sound turned out to be no worse than with a direct connection of headphones to the output of a computer sound card.

Author: M Sapozhnikov, Ganei Aviv, Israel; Publication: radioradar.net

See other articles Section Transistor power amplifiers.

Read and write useful comments on this article.

<< Back

Latest news of science and technology, new electronics:

Artificial leather for touch emulation 15.04.2024

In a modern technology world where distance is becoming increasingly commonplace, maintaining connection and a sense of closeness is important. Recent developments in artificial skin by German scientists from Saarland University represent a new era in virtual interactions. German researchers from Saarland University have developed ultra-thin films that can transmit the sensation of touch over a distance. This cutting-edge technology provides new opportunities for virtual communication, especially for those who find themselves far from their loved ones. The ultra-thin films developed by the researchers, just 50 micrometers thick, can be integrated into textiles and worn like a second skin. These films act as sensors that recognize tactile signals from mom or dad, and as actuators that transmit these movements to the baby. Parents' touch to the fabric activates sensors that react to pressure and deform the ultra-thin film. This ... >>

Petgugu Global cat litter 15.04.2024

Taking care of pets can often be a challenge, especially when it comes to keeping your home clean. A new interesting solution from the Petgugu Global startup has been presented, which will make life easier for cat owners and help them keep their home perfectly clean and tidy. Startup Petgugu Global has unveiled a unique cat toilet that can automatically flush feces, keeping your home clean and fresh. This innovative device is equipped with various smart sensors that monitor your pet's toilet activity and activate to automatically clean after use. The device connects to the sewer system and ensures efficient waste removal without the need for intervention from the owner. Additionally, the toilet has a large flushable storage capacity, making it ideal for multi-cat households. The Petgugu cat litter bowl is designed for use with water-soluble litters and offers a range of additional ... >>

The attractiveness of caring men 14.04.2024

The stereotype that women prefer "bad boys" has long been widespread. However, recent research conducted by British scientists from Monash University offers a new perspective on this issue. They looked at how women responded to men's emotional responsibility and willingness to help others. The study's findings could change our understanding of what makes men attractive to women. A study conducted by scientists from Monash University leads to new findings about men's attractiveness to women. In the experiment, women were shown photographs of men with brief stories about their behavior in various situations, including their reaction to an encounter with a homeless person. Some of the men ignored the homeless man, while others helped him, such as buying him food. A study found that men who showed empathy and kindness were more attractive to women compared to men who showed empathy and kindness. ... >>

Random news from the Archive

Bizen process is better than CMOS 21.10.2019

British companies Search For The Next (SFN) and Semefab have jointly developed a semiconductor manufacturing process that is said to revolutionize the industry.

The developers were not afraid of fundamental changes at the level of transistors and returned to five decades ago, when CMOS technology and field-effect transistors did not yet dominate. The new process, called Bizen, is built on the use of bipolar transistors and the principles of quantum tunnel mechanics. Compared to CMOS, Bizen results in a fivefold reduction in lead times, from the current fifteen weeks to three. In addition, the new process provides a threefold increase in gate density, which corresponds to a threefold reduction in die size. Finally, Bizen halves the number of technology layers required. At the same time, performance and power consumption indicators are achieved, which are characteristic of modern products manufactured using CMOS technology.

Bipolar technology has traditionally been limited due to its requirement for resistors that cannot be reduced to the same extent as active elements. The use of Bizen transistors based on the quantum tunnel effect allows designers to eliminate the resistor, as in MOS devices. This allows for very low power circuits where the transistor is normally on but not saturated and driven by an isolated tunnel junction rather than a straight metal electrode on the base as in traditional bipolar transistors.

The partners believe that Bizen will "set the clock of Moore's law back 10 years" and return many of the previous generation factories back to mass production.

Other interesting news:

▪ Drones are controlled by gestures

▪ Reusable rocket engine

▪ MAXM22510 - isolated RS-485 with built-in power

▪ Molecular machines will provide a breakthrough in medicine

▪ Microrobots for the repair of underground utilities

News feed of science and technology, new electronics

Interesting materials of the Free Technical Library:

▪ section of the Antenna website. Article selection

▪ article You're not in Chicago, my dear. Popular expression

▪ article How big is the solar system? Detailed answer

▪ article Construction and content of labor protection instructions

▪ article Simple hidden wiring finder without power supply. Encyclopedia of radio electronics and electrical engineering

▪ article Imported radiotelephone power supply. Encyclopedia of radio electronics and electrical engineering

Leave your comment on this article:

All languages of this page

Home page | Library | Articles | Website map | Site Reviews