Tiny Amplifier With ATtiny

Small microcontrollers can pack quite a punch. With the right code optimizations and proper use of the available limited memory, even small microcontrollers can do things they were never intended to. Even within the realm of intended use, however, there are still lots of impressive uses for these tiny cheap processors like [Lukasz]’s audio amplifier which uses one of the smallest ATtiny packages around in the video embedded below.

Since the ATtiny is small, the amplifier is only capable of 8-bit resolution but thanks to internal clock settings and the fast PWM mode he can get a sampling rate of 37.5 kHz. Most commercial amplifiers shoot for 42 kHz or higher, so this is actually quite close for the limited hardware. The fact that it is a class D amplifier also helps, since it relies on switching and filtering to achieve amplification. This allows the amplifier to have a greater efficiency than an analog amplifier, with less need for heat sinks or oversized components.

All of the code that [Lukasz] used is available on the project site if you’ve ever been curious about switching amplifiers. He built this more as a curiosity in order to see what kind of quality he could get out of such a small microcontroller. It sounds pretty good to us too! If you’re more into analog amplifiers, though, we have you covered there as well.

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Web Development: What’s Big In 2019?

I try to keep up with web development trends but it’s hard to keep pace since it’s such a fast evolving field. Barely a week goes by without the release of a new JS framework, elaborate build tool or testing suite — all of them touted as the one to learn. Sorting the hype from the genuinely useful is no mean feat, so my aim in this article is to summarise some of the most interesting happenings that web development saw in the last year, and what trends we expect to see more of in 2019.

A technology or framework doesn’t have to be brand new to be on our list here, it just needs to be growing rapidly or evolving in an interesting way. Let’s take a look!

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Transforming A Bookshelf Speaker Into A Portable Boombox

There’s a lot of fun to be had in modernizing an old boombox but what about turning one of those ubiquitous shelf speakers into a portable boombox, complete with a handle for carrying? That’s what [GreatScott] did when a friend gave him a just such a shelf speaker.

These days you’d very likely use your phone as the audio source so he included a 20 watt stereo class D amplifier which could be disconnected at the throw of a switch if not needed. To power the amplifier he used 16 18650 lithium-ion batteries which were leftover from previous projects. He estimates they should give him around 100 hours of enjoyable tunes. And to make further use of the batteries, he also added a USB charger so that he could charge up his phone from it, something else which is nice to be able to do when on the road.

A battery management system (BMS), an XT60 connector for charging the batteries, his battery level indicator circuit which we talked about before, a new passive audio crossover, and some rather nice work on that case all round out the boombox. Check out his full construction in the video below and make sure to stay until the end when he gives a taste of its awesome sound (you may even swear your desk is vibrating from the bass despite wearing earbuds, like we did).

And on the subject of speaker-to-boombox conversions, here’s one from a few years ago which makes use of a car MP3 player module giving it FM, USB, and SD card support.

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DIY Mini-Amp Goes to Eleven

On the day mini-amps were invented, electric guitar players the world over rejoiced.  No longer would they be house-bound when jamming out on their favourite guitar. It is a doubly wondrous day indeed when an electric guitar-inclined maker realizes they can make their own.

[Frank Olson Music] took apart an old pair of headphones and salvaged the speakers — perhaps intending to replicate a vintage sound — and set them aside. Relying on the incisive application of an X-Acto knife, [Olson] made swift work cutting some basswood planks into pieces of the amp before gluing them together — sizing it to be only just bigger than the speakers. A tie was also shown no mercy and used as a dapper grille screen. Both the head and speaker cabinets were sanded and stained for a matching finish.

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Good in a Pinch: The Physics of Crimped Connections

I had a friend who was an electronics assembly tech for a big defense contractor. He was a production floor guy who had a chip on his shoulder for the engineers with their fancy book-learnin’ who couldn’t figure out the simplest problems. He claimed that one assembly wasn’t passing QC and a bunch of the guys in ties couldn’t figure it out. He sidled up to assess the situation and delivered his two-word diagnosis: “Bad crimp.” The dodgy connector was re-worked and the assembly passed, much to the chagrin of the guys in the short-sleeved shirts.

Aside from the object lesson in experience sometimes trumping education, I always wondered about that “bad crimp” proclamation. What could go wrong with a crimp to so subtly futz with a circuit that engineers were baffled? How is it that we can rely on such a simple technology to wire up so much of the modern world? What exactly is going on inside a crimped connection anyway?

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Now is the Golden Age of Artisanal, Non-Traditional Tube Amps

Earlier in the month, [Elliot Williams] quipped that it had been far too long since we saw a VFD-based amplifier build. Well, that dry spell is over. This week, [kodera2t] started showing off his design for a VFD headphone amp.

Here’s the thing, this isn’t using old surplus vacuum fluorescent displays. This is actually a new part. We first covered it about 18 months ago when Korg and Noritake announced the NuTube. It’s the VFD form factor you would find in old stereo and lab equipment, but housed in the familiar glass case is a triode specifically designed for that purpose.

Check out [kodera2t’s] video below where he walks through the schematic for his amplifier. Since making that video he has populated the boards and taken it for a spin — no video of that yet but we’re going to keep a watchful eye for a follow-up. Since these parts can be reliably sourced he’s even planning to sell it in his Tindie store. If you want to play around with this new tube that’s a pretty easy way to get the tube and support hardware all in one shot. This is not a hack, it’s being used for exactly what Korg and Noritake designed it to do, but we hope to see a few of these kits hacked for specific tastes in amp design. If you do that (or any other VFD hacking) we want to hear about it!

And now for the litany of non-traditional VFD amps we’ve grown to love. There is the Nixie amp where [Elliot] made the quip I mentioned above, here’s an old radio VFD amp project, in this one a VCR was the donor, and this from wayback that gives a great background on how this all works.

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Hacklet 85: Alternative Audio Amplifiers

When you think of amplifiers, you’re probably thinking of audio or some big ‘ol power amps for radios. While interesting, there are some very interesting ‘alternative’ amplifiers floating around hackaday.io that are more than just power amps, and exceedingly useful, to boot.

1601181393316190625[Ronald] bought an XMS amplifier a few years ago, and although it worked well, every time he changed the input, the loudness had to be toggled. One thing led to another, and he realized this amplifier had a four-channel audio processor that could be controlled by I2C. This was the beginning of his Network Amplifier.

Inside the box is a Raspberry Pi that controls a PT2314-based amplifier. Also included is a 2×16 character LCD, a few LEDs, switches, and a rotary encoder.  There was an Android app that controlled the amplifier, but this was discarded for a better looking web-based solution. Now [Ronald] has every audio source available over WiFi.

973501443636885535What if you want an audio amplifier without a speaker? Wait, what? That’s what [DeepSOIC] is doing with his experiments in ion wind loudspeakers.

‘Ion wind lifters’ have been around for decades now, mostly in the labs of slightly off-kilter people who believe this is the technology aliens are using to visit earth. Nevertheless, ion wind lifters produce an airflow, and if you make that wind variable, you get sound. Pretty cool, huh?

The amplifier for this project uses a tube to modulate kilovolt supply through the ion ‘blower’. Does it work? Sure does. [DeepSOIC] got a piece of 0.2 mm nichrome wire to discharge ions into the air, after which the ions drift into the second electrode. The result is sound, and the entire project is built deadbug style. It really doesn’t get cooler than this.

 

2981611414932529525Continuing with the tube amp trend, [Marcel] built the cheapest little tube amp around.

The design of an audio tube amp is fairly simple business. First, you start with a big ‘ol transformer, and rectify the AC into DC. This gets fed into a preamp tube, and this is fed into a bigger power tube.

In about 50 years of development, tube designers had the technology down pat by the mid 1950s, and triode/pentode tubes were created. This allowed tube designers to condense two amplifier stages into a single tube. While this setup was usually used for cheap, toy-like electronics, you can still buy the ECL82 tube today.

[Marcel] took one of these tubes, added a rectifier tube, transformer, and big cap to create the simplest possible tube amp. Use it for guitars, use it for hi-fis, it’s all the same. It’s not going to sound great, but it is a very easy amp to build.

All of these interesting audio amplifier projects are curated on this new list! If you have a build that amplifies sound in an interesting way, don’t be shy, just drop [Adam] a message on Hackaday.io and he’ll add it. That’s it for this week’s Hacklet. As always, see you next week. Same hack time, same hack channel, bringing you the best of Hackaday.io!