The hottest Signal Processing Substack posts right now

And their main takeaways
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Top Technology Topics

Choosing an op-amp for your project

lcamtuf’s thing • 4081 implied HN points • 03 Jan 25
🕹 Technology Electronics Engineering Circuit Design Hardware Signal Processing
  1. When selecting op-amps for projects, avoid using older models like LM741 and LM324, as modern options perform much better and are easier to use.
  2. Look for op-amps with rail-to-rail input and output capabilities, which allow for better voltage range handling and simplify your circuit design.
  3. Focus on key parameters like bandwidth, output current, and noise specifications, but remember that many modern op-amps have decent performance that meets the needs of most hobby projects.

The marvelous disappearing capacitor

lcamtuf’s thing • 4285 implied HN points • 07 Dec 24
🕹 Technology Electronics Engineering Physics Signal Processing Innovation
  1. Bootstrapping can significantly improve photodiode amplifier performance by minimizing the impact of parasitic capacitance. This helps in amplifying fast-changing signals better.
  2. A voltage follower in the circuit helps keep the photodiode at the same voltage, preventing internal charging and making it act like an ideal current source.
  3. While bootstrapping boosts performance, real-life limitations exist, like bandwidth and impedance, which need to be considered for accurate designs.

More bits is better, right?

filterwizard • 59 implied HN points • 01 Oct 24
🕹 Technology Signal Processing Quantization
  1. Increasing the bit width of an ADC can improve data accuracy, but it doesn't always work as expected.
  2. Quantization can cause significant errors, especially with low-level signals, leading to misleading results.
  3. Using dither helps improve the accuracy of the signal output from an ADC, making it better for capturing lower signal levels.

Optical Conversion of CMOS <> Superconducting Signals

Tapa’s Substack • 119 implied HN points • 10 Sep 24
🕹 Technology Quantum Computing Electronics Optics Signal Processing
  1. There's a new idea to use light to switch superconducting signals with CMOS circuits. This could help in areas like quantum computing and sensors.
  2. Using light for this switching can provide thermal isolation, which is a big advantage. It makes the connection between different technologies safer and more efficient.
  3. Two methods to switch are discussed: thermal and non-thermal. Non-thermal switching might be better because it's more efficient, using light directly instead of heating things up.

Analyze FIR filters using just high-school algebra

filterwizard • 39 implied HN points • 23 Sep 24
🕹 Technology Signal Processing Mathematics Algebra Engineering
  1. FIR filters have a finite impulse response, meaning they only remember a limited amount of past input. This makes them predictable and stable, especially for applications needing fast settling times.
  2. You can think of FIR filter coefficients as a polynomial, which allows you to use algebra to analyze and create filters. This approach helps in understanding how changing coefficients affects the filter's behavior.
  3. By factoring the polynomial of an FIR filter, you can create smaller filters that combine to produce the same overall effect. This technique allows for a deeper exploration of filter design, giving you more control over the filter's characteristics.
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4.4 Signals Along a Transmission Line

Fields & Energy • 319 implied HN points • 07 Aug 24
🕹 Technology Signal Processing Telecommunications Innovations
  1. Long telegraph cables can cause delays and signal blurring, which was a problem when laying the first transatlantic cable.
  2. Using too much voltage to fix signal issues can break the cable, leading to more problems rather than solutions.
  3. The first successful transatlantic cable started working in 1866, just after an important theory on electromagnetism was published.

Now synthesize your FIR filters using high-school algebra

filterwizard • 19 implied HN points • 27 Sep 24
🕹 Technology Engineering Software Mathematics Signal Processing Computer Science
  1. You can create FIR filters by breaking them down into smaller parts using simple math. This makes it easier to understand how each piece works together.
  2. The sharp notches or deep points in a filter's response happen because of certain factors in the polynomial. Each notch can be traced back to specific frequencies based on these factors.
  3. To improve a filter's performance, you can add more mathematical pieces to make the response smoother in certain areas. This way, you can customize how the filter behaves at different frequencies.

4.3.3 Cross Coupling

Fields & Energy • 259 implied HN points • 31 Jul 24
🕹 Technology Electronics Telecommunications Music technology Signal Processing History
  1. Thaddeus Cahill invented an early electronic music system called the Telharmonium in 1897, aiming to broadcast music through telephone lines. However, his venture failed because the music interrupted phone calls, causing complaints from users.
  2. Cahill's difficulties were largely due to a problem called cross coupling, where signals from one line affect nearby lines. This was common back in the day when many phone lines ran close together.
  3. The situation shows that electrical signals can spread beyond their wires, not just following what we'd think of as direct paths. This understanding is important in telecommunications and electrical engineering.

Which filters are Noisier – Analog or Digital? Part 2

filterwizard • 19 implied HN points • 19 Sep 24
🕹 Technology Signal Processing Circuit Design
  1. When comparing analog and digital filters, analog filters tend to perform better in terms of noise, especially at low frequencies. Digital filters can introduce quantization noise that isn't present in analog filters.
  2. Digital filters, specifically the Direct Form filter, can have significant noise gain, which means they can amplify noise from quantization, making their performance worse in certain situations.
  3. To improve the noise performance of digital filters, increasing the bit depth of the processing can help, but there are also alternative filter topologies that can reduce noise without needing more bits.

When the mask slips - a cautionary (if ancient) tale of IC quality

filterwizard • 59 implied HN points • 01 Sep 24
🕹 Technology Audio engineering Circuit Design Signal Processing Electronics
  1. Don't assume that all ICs perform the same, even if they look similar. Small changes in production can lead to big differences in quality.
  2. Working with audio equipment requires attention to detail in filtering processes. It's essential to ensure that all components meet specific performance standards.
  3. When using older components, always check for changes in manufacturing. Even slight variations can drastically affect audio quality, as seen with the NE5532 op-amps.

Which Filters are Noisier – Analog or Digital? Part 1

filterwizard • 19 implied HN points • 18 Sep 24
🕹 Technology Signal Processing
  1. Analog filters can generate noise from several sources like opamps and passive components. Understanding where this noise comes from helps in designing better filters.
  2. Capacitors don’t create noise themselves, but they can hold noise sampled from resistors. This means their role in noise management in filters is important.
  3. The noise contribution of a filter stays consistent if you keep the capacitor values the same while changing resistors. This knowledge simplifies filter design.

Why does the frequency response of my DAC droop?

filterwizard • 19 implied HN points • 31 Aug 24
🕹 Technology Electronics Signal Processing Engineering
  1. A DAC's output might not represent the input signal accurately because it holds samples longer than expected. This can result in a drooping frequency response instead of a flat line.
  2. The output is shaped by a sinc function, where certain frequencies lose energy and create unwanted noise, making the signal less clear.
  3. Modern DACs, like sigma-delta types, don't have this droop problem. They use faster processes and digital filtering to provide a smoother, more accurate sound.

Not so fast, Mr. Fourier!

lcamtuf’s thing • 119 HN points • 12 Mar 24
🔬 Science Computing Signal Processing Mathematics Algorithms Engineering
  1. The discrete Fourier transform (DFT) is a crucial algorithm in modern computing, used for tasks like communication, image and audio processing, and data compression.
  2. DFT transforms time-domain waveforms into frequency domain readings, allowing for analysis and manipulation of signals like isolating instruments or applying effects like Auto-Tune in music.
  3. Fast Fourier Transform (FFT) optimizes DFT by reducing the number of necessary calculations, making it more efficient for large-scale applications in computing.

Bonus post - Noisy Monitors

Sunday Letters • 59 implied HN points • 07 Feb 22
🕹 Technology Engineering Software Team Management Product Development Signal Processing
  1. Noisy monitors can create problems for engineering teams. They get too many alerts that can drown out the important signals, making it hard to focus on real issues.
  2. Accumulating unresolved bugs and warnings can lead to confusion. Teams might ignore older and less critical issues, which can mask newer problems that need attention.
  3. It's important to maintain discipline and organization in monitoring systems. Just like a chef cleans his kitchen daily, teams should regularly tidy up their alerts and processes to stay effective.

Why I hate Pi Day

Logging the World • 1 HN point • 14 Mar 23
🔬 Science Mathematics Physics Analysis Signal Processing Forensics
  1. Pi Day can be annoying for some mathematicians due to the overemphasis on the beauty of the Pi formula and memorizing digits of Pi.
  2. The beauty in mathematics is not just about formulas like Pi, but also in the precise form of logical arguments and the way pieces fit together like a complex mechanism.
  3. Fourier analysis, involving Fourier transform and harmonics, is a powerful tool used in various scientific fields beyond Pi Day celebrations.

How linear-phase filters can still cause phase distortion

filterwizard • 0 implied HN points • 14 Sep 24
🕹 Technology Signal Processing Audio engineering Data Analysis Filters
  1. Even though linear-phase filters are supposed to keep the phase of signals the same, they can still cause unexpected phase changes. This can happen especially at stopband frequencies where the phase might jump abruptly.
  2. Using simple filters, like box-car filters, can lead to problems because they may not completely block unwanted frequencies. This can result in the output signal being inverted or misinterpreted, especially when analyzing important data trends.
  3. It's important to choose the right filter. Either use filters that effectively block unwanted frequencies or ones that don’t cause abrupt phase changes, to avoid messing up the signals you are trying to interpret.

The Chronicles of GND, Part 3

filterwizard • 0 implied HN points • 25 Sep 24
🕹 Technology Electronics Engineering Semiconductors Signal Processing
  1. Opamps have three important terminals: positive supply, negative supply, and output, and the total current flowing into them should always equal zero.
  2. The output stage of an opamp affects how it behaves, especially whether it's in class A, B, or AB, which changes the current it draws from the power supply.
  3. Designing a circuit properly means understanding how to connect power supplies without causing distortion in the output, especially if you're working on high-quality audio projects.

My 1986 exploration of subtractive crossovers 'done my way'

filterwizard • 0 implied HN points • 27 Aug 24
🕹 Technology Audio engineering Signal Processing
  1. When you combine highpass and lowpass filters, you often don't get the original signal back, which can affect how music sounds. This can be a problem because the phase shift isn't what you'd expect from just delaying the signal.
  2. In the past, before digital processing was common, there was a big need to find better ways to design these filters. One solution was to use a subtractive method to reduce the 'insult' to the signal.
  3. The work from the mid-80s shows that by carefully designing analog filters and using subtraction, you can achieve a closer match to the original signal without extra distortion.

Group Delay Eq and Crossover design, two links

filterwizard • 0 implied HN points • 24 Aug 24
🕹 Technology Audio engineering Signal Processing Research Papers
  1. Adding transmission zeroes to crossover filters can enhance their performance, similar to elliptic filters, even if that resemblance is just superficial.
  2. Charlie Laub has published valuable articles that detail this crossover filter design improvement, and there’s additional material available for deeper understanding.
  3. The importance of group delay in audio engineering is backed by research, which could benefit those looking to explore time domain behaviors in their designs.

Prediction and negative-delay filters: five things you should know

filterwizard • 0 implied HN points • 19 Aug 24
🕹 Technology Filters Signal Processing Data Analysis
  1. Filters can delay signals as they take time to process inputs and produce outputs. It's important to understand this delay, especially when working with different types of signals.
  2. While you can't completely eliminate delay in filters, you can create compensating filters to achieve zero or even negative group delay at certain frequencies. This can improve the accuracy of your system responses.
  3. Negative-delay filters can actually predict future values of a signal based on its current ramping behavior. This can be really useful in control systems and financial data analysis.

How to turn linear phase into truly linear phase

filterwizard • 0 implied HN points • 17 Sep 24
🕹 Technology Signal Processing Filters Digital Design Electronics
  1. FIR filters can have phase jumps that can affect signal quality. To fix this, one method is to use two filters in series, which cancels out unwanted phase jumps.
  2. Another approach involves tweaking the filter's impulse response to eliminate negative values in the Fourier transform. This ensures a smoother phase response without major changes to the filter's function.
  3. It's important to over-design the filter's stopband due to the adjustments made. This way, the overall performance remains reliable and avoids distortion in the filtered signals.

Measurement noise: when 1000*1000 isn't a million

filterwizard • 0 implied HN points • 03 Oct 24
🕹 Technology Electronics Engineering Measurement Data Analysis Signal Processing
  1. Measurement noise can make it seem like you need very high accuracy to get correct results, but you might actually need less than you think.
  2. For measuring small signals accurately, the required dynamic range isn't as extreme as multiplying the signal by itself; practical calculations can simplify this.
  3. For specific accuracy requirements in noisy environments, using embedded microcontroller ADCs can be a good solution to achieve realistic signal-to-noise ratios.