Feedback & Error Correction Master Class!
Some time ago I did a presentation for Menno vanderVeen's Tube Society, on feedback and error correction. The folks at Elektor International Media taped the whole shebang (I talked for more than three hours!) and the result is a very nice DVD. It has the presentation, or, as they call it, the Masterclass, plus a sizeable number of articles and background papers, as well as the sheets I used.
In this Masterclass I address several aspects of feedback in audio amplifiers. The focus of this Masterclass, although not entirely math-free, is on providing insight and understanding of the issues involved. Amongst others, I talk about:
- Basics of negative feedback and its influence on amplifier parameters;
- ‘Gotchas’ like Slew Rate Limiting;
- The impact of feedback on internal overload;
- Stability of feedback amplifiers;
- Feedback ‘speed’ and the difference between delay and phase shift;
- Positive feedback and its effects;
- Simultaneous application of positive and negative feedback in a 50-ies tube amplifier;
- Error Correction according to professor Malcolm Hawksford;
- Error Correction as used in the paX amplifier as published by Elektor in April and May 2008;
- Feedback or Error Correction - a case study: QUAD Current Dumping.
This Masterclass provides a clear overview of the benefits that can be obtained by feedback and its sibling, error correction; but also of its limitations and disadvantages. Note: This Masterclass is also available in the German language.
New Linear Audio Volume just out - Volume 5!
Exciting, inspiring and interesting articles from an international team of great authors, some well known, some soon-to-be well known without doubt!
Tutorials - How do you size those snubbers across rectifiers – and do they work at all? Morgan Jones decided to find out and found some unexpected answers in Rectifier snubbing – background and Best Practices.
After years of trying to recreate the Big Bang, Erik Margan returned to audio to tell all about Interconnections in Audio.
Pierre Touzelet completes his investigations in transformers writing On stray capacitances in audio transformers.
Technology - Not everyone is convinced that SACD really sounds better than red book CD. Hans van Maanen is, and he presents investigations and findings to back up his experiences On the audibility of “high resolution” digital audio formats and how to test this.
Circuit design - An RIAA corrected preamp is fine for contemporary vinyl, but for recreating the sound of 100 years old discs and cylinders, you need An Archival Phono Preamplifier – and Gary Galo designed one.
After exploring the F-word, Bruno Putzeys is back with the next letter in the alphabet: The G-word, or How to Get Your Audio off the Ground – providing insight and Best Practices for clean audio. As a first for Linear Audio, a free PCB*, courtesy eurocircuits.com, is included for Bruno’s demo preamp project.
Circuit design can be fun, and sometimes the challenge also lies in making do with what you happen to have available, as shown by Rob Scheepens in The parts bin headphones amplifier.
Tone controls are sometimes eschewed by purists, but Douglas Self shows that this is unwarranted and that you can design flexible, transparent and effective tone controls in A low-noise preamplifier with variable-frequency tone controls.
System design - How do you increase your enjoyment of reproduced audio if your whole system has already been optimized? Use High Frequency Reverberation for finer sound reproduction says Richard Burwen.
Speaker Clinic - Rather than designing a speaker from the ground up, Lennart Jarlevang accepted The Small Speaker challenge to improve on what was already a well-regarded product.
The Way I see it… - Our columnist Stan Curtis addresses that seemingly unresolvable dichotomy between what sounds best to you and objective technical performance. His Listening to paradoxes delves a little deeper in the underlying issues.
Book review - Stuart Yaniger reviews Oliver Masciarotte’s To Serve and Groove and finds both strong and less so points.
*As long as stocks last.