Electronics with passion: amplifiers and power supplies, FET's and vacuum tubes..

Quick How-To: build a custom Linux kernel (CentOS 6.4 x64 minimal)

How to (re)build a custom kernel on CentOS There are plenty of how-to's about building vanilla kernel on all types of Linux'es. The top of the search results tell you about "the CentOS way" of building new kernel - using rpm etc. It might be the "right way" of obtaining a custom kernel, but it did not fit into my brains even after few reading attempts :) Hence this simplified old-style procedure, that proved to work well on modern CentOS.


I needed to get rid of kipmi0 process clogging CPU

OpAmp + MOSFET = a decent headphone amplifier

Headphone amplifier and Sennheiser HD-580[Читать на русском]

Flood in the Internet

These days search engines throw tons of schematics of "Class A headphone amplifiers" on us. There we can find anything: from monsters capable of driving big loudspeakers to humble OpAmps heavily loaded by 30 Ohms without any hope for help. The big wave of so-called hybrid headphone amps is scary:

Coming soon

Dear friends, I have to apologize for not posting much on this blog lately. The reason is simple: I am swamped by the development of this site's Russian twin. There…

100KHz square wave generator for testing audio amplifiers


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The musical signal's form does never resemble a square wave. The frequency range perceived by an average adult hardly goes above 17KHz. Hence I do not give a dime to those heated discussions whether it's appropriate to test audio amplifiers using a 100KHz meander signal. But being an electronic engineer in my heart as well as by education and passion - I can assure you that giving an audio amplifier a try with 100KHz square wave test signal can reveal quite some technical qualities (or lack of those) in the design. Overshots caused by negative feedback loops or signal slopes formed by input/Miller capacitances are amongst things that are easier to observe with meander than when using sound-frequency test signal.

Simple high-quality saw-tooth test signal generator

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Honestly, I would not claim that a saw-tooth signal is crucial for tuning audio amplifiers and similar stuff. It's rather a matter of convenience and helps to spot several non-linearities easier than a sine-wave.

Budget Wien bridge oscillator with low THD

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    How can one tune the best in class audio amplifier without using a top quality signal source? DIY Wien bridge oscillator comes to rescue!  

In this article:

  • Linearity of professional equipment using budget OpAmps
  • Low distortion precision AGC
  • Can be battery operated: minimized EMI

How things began

Web site backup and upload: rsync over sshfs (GoDaddy or other hosting with ssh access)

Other good people provided ideas for this solution: notbrainsurgery @ livejournal Robert @ softwarerevisions.blogspot.com For some reason GoDaddy jailed hosting does not provide rsync, while it allows ssh user sessions to the host. It's not obvious how to move big chunks of data without "resume" functionality. Even worse for backup needs... Here's one of possible solutions based on my own experience. I hope this post could help someone too :)

How did I discover and recover USB key disk geometry (on Linux)

It's relatively easy to screw the partition table on a USB key. I happened to have a quality 16GB USB key that got it all wrong (due to some of my experiments in the past :) - it was presenting itself as 250G drive. fdisk, sfdisk and hdparm all showed wrong disc geometry. I'd be happy to possess a little jewelry of 250GB, but I am afraid we'll have to wait a year or two for these to come. Sure I'd have problems should I try to use it as is for anything...Getting it all right turned out to be very simple - once I found what to do.

High Current LDO Linear Voltage Regulator – the sequel

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The previous article about a nearly ideal LDO regulator gained quite some interest amongst readers. Meanwhile I managed to build two "barrel" multi-purpose power supplies based on this LDO circuit.

Working Prototype

Casing was always the biggest doubt in my DIY projects. Here I resorted to nice and cheap stainless-steel cans from Ikea with covers cut from a 6mm thick MDF. Perfect solution... to be stuck behind the desk.
120W barrel power supply

MOSFET + TL431 = LDO Linear Voltage Regulator

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Ideal LDO Voltage Regulator

LDO = low dropout
Ideal Low Dropout Linear Voltage Regulator ;)
Such a popular three-pin voltage regulator as LM317 (datasheet) is specified to work at minimum 3 Volts across the chip. This humble parameter is not even stated directly in the datasheet: I found it only