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Updated as of date of current article

Audio Home Page

Circuits or calculations should not be breadboarded until they are proven by SPICE simulation. Even then breadboard and test a prototype before committing to a final circuit. Unproven circuits or ideas are for mental stimulation only. Note also that mistakes usually go unnoticed until I find and fix them; therefore I recommend letting ideas sit for a while before considering them complete. For this same reason I try to provide proofs where reasonable or possible so that the user of an idea can verify it before use.

First Things

Audio Philosophy August 5, 2011
Intellectual Property Concerns August 5, 2011. Declaring your freedom to use DIY ideas.

Theory

Phono Equalization Calculations Updated March 23, 2011. Added Passive RIAA Network with Extra Zero.
When Is Phase Shift not Phase Shift? January 2, 2009
Linear Phase Sinc Compensation Filter for Zero-Oversampling DACs January 26, 2009
Mathematical Consideration of Some of the Limitations of Digital Audio May 23, 2009
Phono Termination Calculations and Calculator August 10, 2009. Updated April 23, 2012 Added mouse functions for graph examination to new program version 3.2.0. Documented at instruction 7. Updated April 23, 2012 Fixed program malfunction causing wrong -3dB right mouse button result for Q < 0.7071 raising program version to 3.2.1. Updated April 30, 2012 Raised program version to 3.2.2 incorporating faster graph updates under mouse inspection.
Active Inductor Load Updated March 11, 2010. Changed designation for MOSFET constant to proper k_n.
Power Supply Ripple Calculations and Capacitor Size December 6, 2009
Simple Noise Calculations Updated February 27, 2010. Recalculated RIAA noise bandwidth by numerical integral.
Musical Feedback Amplifiers Updated November 2, 2010. Added AD847 to list of Possibly Musical IC Operational Amplifiers and a link to its datasheet.
Simple DC Servos Updated July 21, 2010. Spice verified. First order servos reduce amplifier DC offset without fear of oscillation. Musical Feedback Amplifier example. Elaborated servo equations to better clarify integrator response.
A Musical View of Distortion August 31, 2010
Transfer Curve Shape and Distortion January 1, 2011. Multiple bends in transfer functions reduce distortion quality. Updated January 6, 2011. Added investigation into distortion masking and made an immediate model correction to same.
Flicker Noise Calculations January 26, 2011. Noise of unknown origin causes a rise in noise at low frequencies.
Managing TIM February 26, 2011. Practical means to avoid a difficult-to-measure form of distortion.
Distortion Cancelation May 26, 2011. Three simple distortion cancelation concepts. Updated May 31, 2011. Added SPICE verification of voltage mirrors. Updated June 8, 2011. Recommended use of voltage mirror for BJT circuits only for unity gain pending further investigation. SPICE results problematic with gain, only unity gain producing the desired results. See text. Updated June 11, 2011 Added SPICE verification of integer-gain BJT voltage mirror.
Optimizing the Class B Emitter Follower August 5, 2011. Is current drive better than voltage drive?
Local Feedback August 27, 2011. Is Local Feedback the same concept as Global Feedback?
Apples and Oranges October 2, 2011. A simple proof that class-A and class-B distortion specifications are not comparable.
Phono Preamp Input Protection November 3, 2011.
Transistor Preference December 14, 2011. The effect of transistor choice on distortion performance
One-Bend Amplifier January 31, 2012. Part 1: Compare a current-feedback amplifier allowing a one-bend distortion characteristic to its voltage-feedback equivalent. Updated March 14, 2012 Added correction concerning output stage transconductance factor and added a link to the next article.
Digital Audio Formats April 18, 2012. Updated April 19, 2012 Added graph illustrating how oversampling improves analog filter application. Updated April 20, 2012 Added extra material correcting presumptions contrary to the limitations of the successive-approximation ADC.

Application

Line Level Class A Power Supply Updated March 11, 2010. Corrected for improper g_fs presumptions.
Low Noise 2-Stage All JFET Phono Preamp Updated July 2, 2010. SPICE verified. Recalculated with 48V power supply and RIAA standard gain.
A Linear Logarithmic Volume Control September 29, 2010.
Low-noise Hybrid Op-amp/Discrete Phono Preamp October 29, 2010. SPICE verified. Desire discrete output buffer to add neutral euphony to nearly distortionless op-amp preamp. Updated October 29, 2010 Improved visibility of graphs. Updated October 30, 2010 Added links to semiconductor datasheets in parts list. Move class-a bias to connect to positive supply, and verify no operational changes.
Cascode Selector November 17, 2010. SPICE verified. Audiophile-grade semiconductor selector for input or other switching. Updated November 27, 2010. Added power supply recommendations and a schematic for an LED indicator.
Cascode Phono Preamplifiers May 3, 2011. SPICE verified. Capacitively coupled cascode enables an easily adjustable single-stage preamp. Updated March 3, 2012 Added transfer error curve analysis for both circuits.
One-Bend Amplifier March 14, 2012. Part 2: Improving important details of a current-feedback amplifier.

Downloads

CD Exerciser – Improve your CD player with a homemade test disk April 20, 2009
Op Amp Noise Calculator Updated January 17, 2011. Added considerable new program functionality including accounting for flicker noise.
Phono Termination Calculations and Calculator Details in Theory above.
FETCurve June 26, 2011. A FET parameter calculator. Updated June 26, 2011 Added section on software input limitations specifying some data pitfalls.

Obsolete

JFET Phono Preamp - Active Inductor Example Updated March 11, 2010. Corrected for improper g_fs presumptions.
Low-Noise JFET Phono Preamp - Active Inductor Example This is a redesign using LSK170 JFETs on the input. Updated March 11, 2010 Corrected for improper g_fs presumptions.

External Links

Real Stereo program sponsored by TNT-Audio

Affordable$$Audio Internet audio magazine archives, just merged into HiFi Zine below (subjectivist, some advertising)
Audiophilia Internet audio magazine (subjectivist, some advertising)
AudioWorld Web Directory This website has reverted to an Audio Web Directory again for now.
AudioXpress Website of print audio magazine emphasizing DIY (subjectivist/objectivist, some articles on website)
Enjoy the Music Internet audio magazine (subjectivist, some advertising)
High-end Audio The personal audio website of Arthur Salvatore (subjectivist, no advertising).
High Fidelity Internet audio magazine (subjectivist, some advertising)
Hi-Fi Choice Website of print audio magazine (subjectivist/objectivist, some articles on website)
Hi-Fi News & Record Review Website of print audio magazine (subjectivist, some articles on website)
HiFi Zine Independent internet audio magazine (philosophy?, some non-audio ads)
Positive Feedback Internet audio magazine (subjectivist, some advertising)
Six Moons Internet audio magazine (subjectivist, some advertising)
SoundStage! HiFi Internet audio magazine (subjectivist, some advertising)
Stereophile Website of print audio magazine (subjectivist, some articles on website)
Stereo Times Internet audio magazine (subjectivist, some advertising)
TNT-Audio Independent internet audio magazine (subjectivist, no advertising)
Ultra High Fidelity Magazine Website of print audio magazine (subjectivist, interesting general hifi reading on website, but no magazine articles)