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: Continue reading
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.
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. I've assembled this generator in order to top off the Wien bridge based sine wave generator. Since then I use it regularly because it helps to reveal subtle oscillation issues in amplifiers way better that any sine or square wave can do.
How can one tune the best in class audio amplifier without using a top quality signal source? DIY Wien bridge oscillator comes to rescue!
Most of these questions and answers are coming from discussions with friends. Hence the style.
Q:
Want to see the scope traces, square wave if possible
A:
Continue reading
At a first glance there's nothing difficult in building a unity-gain preamp: the well known and fairly simple source follower should do the job. However in my case it turned out to be quite an adventure. Why "HotFET" - please refer to this article.
| HotFET-Pre (c) - prototyped in a "networking" case |
The design is pretty simplistic. There were many calculations, tests and Continue reading
| HotFET Pre - prototype |
The story has begun long ago with the perplexity caused by the fact that amplifiers based on vacuum tubes consume lots of power, get hot and do sound great; while the vast majority of silicon-based audio devices can stay cool and produce somewhat mediocre results. It did not feel right. Hence my attempt to bring some extra controversy into the world of high definition sound reproduction.
The basic idea of this design was: let's put transistors into the "hot operation mode". Continue reading
LM317 appears to be the most appreciated CCS building block amongst solder-slingers
(term (c) John Broskie).
Personally I never felt relaxed having such a complex OpAmp-based circuit in the audio-signal path. Nevertheless many routinely utilize this type of CCS in audio, including "pure" tube designs.
Recently I was playing happily around cascoding JFETs and MOSFETs for the CCS in my own design. Continue reading
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