Dale Shpak

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Dale Shpak

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  • 05.30.2017
  • Bringing pro-audio high-fidelity features to mobile devices
  • Thanks for bringing high-fidelity audio to the forefront. However, well-designed digital filters to not remove pre-ringing, rather, they do not cause pre-ringing. Pre-ringing is commonly due to the inappropriate use of linear-phase FIR filters in audio systems ... these filters should not be used for audio because their symmetry results in a delayed signal having anti-causal components (the pre-ringing). Minimum-phase filters with bad phase response don't sound good either. And, all of this is to no avail if the digital source material does not meet a high production standard. Much of what is called "music" has been carelessly recorded or overly processed in the studio (e.g., multiple passes through effects devices) and can therefore never be high-fidelity. Similarly, high fidelity is lost if the amplifier and sound drivers following an excellent DAC are of low quality. Problems in the marketplace: 1) Most people have low expectations of audio since they have probably never heard actual high-fidelity sound and they may be listening to hopeless poorly-produced sound anyway. 2) Although MP3s sound flat and lifeless, people are willing to pay money for MP3s. Full price for just some of the bits. 3) A good signal chain (including drivers) is not cheap. I'm with Neil Young on this one. Well-produced music played through a system that respects high fidelity end-to-end is something for the ears to behold.
  • 03.01.2017
  • Grammar and the engineer
  • "Free range eggs" are range eggs with very attractive pricing, whereas free-range eggs are from The Happy Chicken Farm. A simple test to check if you should have a hyphen: Put your finger over each one of the modifiers. If you end up with the wrong meaning (e.g., "free eggs"), you need the hyphen. If you write specifications, patent applications, or even good papers you must employ all of the tools for excellence in writing to be certain that your words cannot be misconstrued.
  • 08.15.2016
  • Monolithic JFETs are alive and well
  • I'd be interested to see how these perform in high-end applications such as microphone, phono, and hydrophone preamps. Having started as a hobbyist in '65 (discrete components only, of course) and having designed a small IC in '84 (LDI ladder lowpass filter in 3 um CMOS), I still value the elegance, performance, and value of the appropriate use of discretes. Sometimes an IC is the wrong solution. I'm currently using some discrete transistors in very low-power sensor network circuits (analog and digital).
  • 06.23.2016
  • Moving averager rejects noisy outlier values
  • Robustness should also be considered. Let's say that the filter's output for a temperature sensor currently represents 20 C and then the sensor fails, generating an ADC value representing 125 C to the input of the filter. The output would remain at 20 C because the filter rejects step changes.
  • 06.23.2016
  • Moving averager rejects noisy outlier values
  • With this approach, you need to be careful that the first samples are representative of a slowly-changing long-term value of the signal because any rapid change in the signal would be ignored. e.g., Let's say that the circuit is starting up and the first input values are zero and then the input value rapidly changes to some value that is far from zero ... the output would remain at zero. For rejecting impulsive noise ("outlier spikes"), rather than weak additive Gaussian noise, ordered-statistic filters such as a median filter or the alpha-trimmed mean filter should be considered.
  • 11.08.2015
  • What's a stereo system, anyway?
  • Treat yourself and take the time to sit down, relax, and listen to your favorite, well-engineered, well-produced music on the best audio system that you can find. Hopefully, you will discover (or re-discover) why some of us do this whenever we can. You could even try some concurrent processing: reading a book while you listen. It sure beats the banality of TV. “Music produces a kind of pleasure which human nature cannot do without.” ― Confucius, The Book of Rites
  • 05.29.2015
  • Mojo, voodoo & secret sauce: The quest for the perfect guitar tone
  • The even-order harmonic distortion with its musically-related harmonics of my hifi tube amp makes it sound "sweeter" than my transistor amp. If you have MATLAB and want to look at the harmonics of symmetric vs. asymmetric distortion: Fs = 96000; % Sampling Frequency F = 1000; % Sine Frequency N = 10; % Number of cyles Np = (N * Fs/F); % Number of points s = sin(2*pi*(1:Np)*F/Fs); % Sine wave s2 = (s+1).^1.4; % Asymmetric nonlinearity s3 = abs(s).^1.4 .* sign(s); % Symmetric nonlinearity s4 = s; % Hard clipping s4(s > 0.8) = 0.8; s4(s < -0.8) = -0.8; s2 = s2 - mean(s2); % Remove DC figure(1); plot(x, [s2' s3' s4']) [h2,f] = freqz(s2, 1, 4096, Fs); [h3,f] = freqz(s3, 1, 4096, Fs); [h4,f] = freqz(s4, 1, 4096, Fs); plotIndex = 1:4096*10000/48000; g2 = abs(h2(plotIndex)); g3 = abs(h3(plotIndex)); g4 = abs(h4(plotIndex)); figure(2); plot(f(plotIndex), 20*log10([g2/max(g2) g3/max(g3) g4/max(g4)])); axis([0 10000 -60 0]) xlabel('Frequency (Hz)'); ylabel('Normalized Magnitude (dB)'); legend ('Symmetric Distortion', 'Asymmetric Distortion','Hard Clipping');
  • 02.20.2015
  • Black Friday: The Avro Arrow tragedy
  • The Arrow was about a decade ahead of its time. It was cancelled due to the incredible naivety of the Progressive Conservative Prime Minister of the day, who willingly (willfully?) kowtowed to US interests. Today, Canada has a Prime Minister with the same propensities: Stephen Harper.
  • 08.11.2014
  • Hybrid vacuum tube/solid-state audio power amplifier
  • Clarification: Perfect fifth is a 3:2 ratio. Starting with a 1,000Hz note, 2,000 Hz is an octave, 4,000 Hz is two octaves higher – both the same note of the scale. 6,000 Hz is two octaves up plus a perfect fifth.
  • 08.11.2014
  • Hybrid vacuum tube/solid-state audio power amplifier
  • Tube amps sound different from SS. 1) I have a class-D Esoteric amp driving large Manger speakers. Scarily accurate. (An accomplished acoustic musician friend remarked "I can hear every tiny mistake" when he listened to his own CD). 2) Also a Sophia Electric tube amp driving smaller Totem speakers. This system sounds "sweet" in comparison. Very nice, especially for listening to old jazz recordings. Perhaps more forgiving. In addition to warm even-order harmonics (musically-related octaves and perfect fifths), tubes are inherently more linear and amps can be built with no feedback, so no TIM. Kudos to the tube wizards. Listen to what you prefer, but never MP3s (flattened music at the same price as uncompressed).