It’s been a while since the last installment in our Know Audio series, in which we investigated distortion as it applies to Hi-Fi audio. Now it’s time to return with part two of our look at distortion, and attempt some real-world distortion measurements on the bench.
Last time, we examined distortion from a theoretical perspective, as the introduction of unwanted harmonics as a result of non-linearities in the signal path. Sometimes that’s a desired result, as with a guitar pedal, but in a Hi-Fi system where the intention is to reproduce as faithfully as possible a piece of music from a recording, the aim is to make any signal path components as linear as possible. When we measure the distortion, usually expressed as THD, for Total Harmonic Distortion, of a piece of equipment we are measuring the ratio of those unwanted harmonics in the output to the frequencies we want, and the resulting figure is commonly expressed in dB, or as a percentage. Continue reading “Know Audio: Distortion Part Two”→
The MOS Technologies 6581, or SID, is perhaps the integrated circuit whose sound is most sought-after in the chiptune world. Its three voices and mix of waveforms define so much of our collective memories of 1980s computing culture, so it’s no surprise that modern musicians seek out SID synthesisers of their own. One of these is the MIDISID, produced by [MIDI IN], and in a recent video she investigates an unexpected tuning problem.
It started when she received customer reports of SIDs that were out of tune, and in the video she delves deeply into the subject. The original SID gained its timing from a clock signal provided by the Commodore 64, with thus different timing between NTSC and PAL versions of the machine. This meant European SID music needed different software values to American compositions, and along the way she reveals a localisation error in that the British Commodore 64 manual had the wrong table of values.
Modern SIDs are emulated unless you happen to have an original, and her problem came when switching from one emulated SID to another. The first one used that clock pin while the second has its own clock, resulting in some music being off-tune. It’s a straightforward firmware fix for her, but an interesting dive into how these chips worked for the rest of us.
Lithium-ion cells deliver very high energy densities compared to many other battery technologies, but they bring with them a danger of fire or explosion if they are misused. We’re mostly aware of the battery conditioning requirements to ensure cells stay in a safe condition, but how much do we know about the construction of the cells as a factor? [Lumafield] is an industrial imaging company, and to demonstrate their expertise, they’ve subjected a large number of 18650 cells from different brands to a CT scan.
The construction of an 18650 sees the various layers of the cell rolled up in a spiral inside the metal tube that makes up the cell body. The construction of this “jellyroll” is key to the quality of the cell. [Lumafield’s] conclusions go into detail over the various inconsistencies in this spiral, which can result in cell failure. It’s important that the edges of the spiral be straight and that there is no electrode overhang. Perhaps unsurprisingly, they find that cheap no-name cells are poorly constructed and more likely to fail, but it’s also interesting to note that these low-quality cells also have fewer layers in their spiral.
We hope that none of you see more of the inside of a cell in real life than you have to, as they’re best left alone, but this report certainly sheds some light as to what’s going on inside a cell. Of course, even the best cells can still be dangerous without protection.
I think most of us who make or build things have a thing we are known for making. Where it’s football robots, radios, guitars, cameras, or inflatable textile sculptures, we all have the thing we do. For me that’s over the years been various things but has recently been camera hacking, however there’s another thing I do that’s not so obvious. For the last twenty years, I’ve been interested in computational language analysis. There’s so much that a large body of text can reveal without a single piece of AI being involved, and in pursuing that I’ve created for myself a succession of corpus analysis engines. This month I’ve finally been allowed to try one of them with a corpus of Hackaday articles, and while it’s been a significant amount of work getting everything shipshape, I can now analyse our world over the last couple of decades.
The Burning Question You All Want Answered
Battle of the Boards, over the decades.
A corpus engine is not clever in its own right, instead it will simply give you straightforward statistics in return for the queries you give it. But the thing that keeps me coming back for more is that those answers can sometimes surprise you. In short, it’s a machine for telling you things you didn’t know. To start off, it’s time to settle a Hackaday trope of many years’ standing. Do we write too much about Arduino projects? Into the engine goes “arduino”, and for comparison also “raspberry”, for the Raspberry Pi.
What comes out is a potted history of experimenter’s development boards, with the graph showing the launch date and subsequent popularity of each. We’re guessing that the Hackaday Arduino trope has its origins in 2011 when the Italian board peaked, while we see a succession of peaks following the launch of the Pi in 2012. I think we are seeing renewals of interest after the launch of the Pi 3 and Pi 4, respectively. Perhaps the most interesting part of the graph comes on the right as we see both boards tail off after 2020, and if I had to hazard a guess as to why I would cite the rise of the many cheap dev boards from China.
Over the years, we’ve brought you many stories of the creative artwork behind electronic event badges, but today we may have a first for you. [Spencer] thinks nobody before him has made a badge powered by a Z80, and we believe he may be right. He’s the originator of the RC2014 Z80-based retrocomputer, and the badge in question comes from the recent RC2014 Assembly.
Fulfilling the function of something you can write your name on is a PCB shaped like an RC2014 module, with LEDs on all the signal lines. It could almost function as a crude logic analyser for the system, were the clock speed not far too high to see anything. To fix this, [Spencer]’s badge packs a single-board RC2014 Micro with a specially slow clock, and Z80 code to step through all memory addresses, resulting in a fine set of blinkenlights.
Thus was created the first Z80-based event badge, and we’re wondering whether or not it will be the last. If you’re curious what this RC2014 thing is about, we reviewed the RC2014 Micro when it came out.
In Europe, where this is being written, and possibly further afield, news reports are again full of drone sightings closing airports. The reports have come from Scandinavia, in particular Denmark, where sightings have been logged across the country. It has been immediately suggested that the Russians might somehow be involved, something they deny, which adds a dangerous geopolitical edge to the story.
To us here at Hackaday, this is familiar territory. Back in the last decade, we covered the saga of British airports closing due to drone sightings. In that case, uninformed hysteria played a large part in the unfolding events, leading to further closures. The problem was that the official accounts did not seem credible. Eventually, after a lot of investigation and freedom of information requests by the British drone community, there was a shamefaced admission that there had never been any tangible evidence of a drone being involved.
In the early 1980s, there was the IBM PC, with its 4.77 MHz Intel 8088 processor. It was an unexpected hit for the company, and within a few years there were a host of competitors. Every self-respecting technology corporation wanted a piece of the action including processor manufacturers, and among those was NEC with their V20 chip and its V30 sibling. From the outside they were faster pin-compatible 8088 and 8086 clones, but internally they could also run both 8080 and 80186 code. [The Silicon Underground] has a look back at the V20, with some technical details, history, and its place as a PC upgrade.
For such a capable part it’s always been a surprise here that it didn’t take the world by storm, and the article sheds some light on this in the form of an Intel lawsuit that denied it a critical early market access. By the time it was available in quantity the PC world had moved on from the 8088, so we saw it in relatively few machines. It was a popular upgrade for those in the know back in the day though as it remains in 2025, and aside from its immediate speed boost there are a few tricks it lends to a classic PC clone. The version of DOS that underpinned Windows 95 won’t run on an 8086 or 8088 because it contains 8016 instructions, but a V20 can run it resulting in a much faster DOS experience. One to remember, if an early PC or clone cones your way.
