Hi-Fi Combines Best Of 60s And 90s Technology

The 90s were a dark time for audio equipment, literally and figuratively. Essentially the only redeeming quality from the decade of nondescript black plastic boxes was the low cost. Compared to the audio equipment of the 60s, largely produced in high-end enclosures with highly desirable tube amplifiers, the 90s did not offer much when it came to hi-fi stereo sound. However, those cheap black boxes from the 90s turn out to be surprisingly perfect for project enclosures for other amplifier builds, such as this 60s-era tube amp recreation.

This mesh of the best of two distinct decades comes from [Alvenh] and begins by preparing the old enclosure for its new purpose. This means a lot of work fabricating a custom metal face plate for the new amplifier and significantly modifying the remaining case. After the box is complete, the amplifier build began. It uses a tube-based preamp and a solid-state power amplifier since [Alvenh]’s experience suggested that the warm tube sound was generated mostly in the preamp. This means that his design is a hybrid but still preserves the essential qualities of a full tube build.

The build also includes a radio module that has the ability to cover the 2m and 70cm bands popular in ham radio. This module also has been found to have much better audio quality than the standard AM/FM receiver typically used in projects like this. With the radio module added to the custom enclosure, as well as a phono amp and a power supply, [Alvenh] has an excellent audio amplifier in an inexpensive case which preserves the tube sound from the true hi-fi eras of decades past.

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Woofer-Based Parts Cleaner Bounces To The Beat

Is there anything more satisfying than building a useful machine from mostly junk? We think not. [ke4mcl] is a big fan of reusing and repurposing things before settling for the recycle bin, and was in the market for a vibratory parts tumbler to quickly clean off old, rusty bits and bobs in the course of repairing old electronics. For just $10, most of which went into a new tube of RTV silicone, [ke4mcl] built their own tumbler and came away with a reusable amplifier setup in the process.

We’ve all seen speaker cones dance, and they are definitely our favorite way to observe non-Newtonian fluids. This old woofer can still move, so it’s got a second life shaking sand and screws around until they’re somewhat shiny. The ideal woofer for this purpose has a rubber surround — that’s the ring that connects the speaker cone to the frame. [ke4mcl]’s foam-surrounded woofer works just as well, though it may not last as long.

After scrounging a container with a screw-top lid that fits the woofer perfectly, [ke4mcl] joined them together with a bead of RTV silicone. Since there weren’t any amplifiers lying around, [ke4mcl] spent a few bucks on a class D amplifier board and found a spare laptop brick to power it. An old phone with a tone generator app gets the sand churning with a friendly sine wave, which you can see in the videos after the break.

We think it’s particularly nice to keep things like fire extinguishers out of the landfill. If you don’t need a parts tumbler, why not use one to make your own refillable, re-pressurizable solvent container?

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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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