[Gregory] is building some microwave gear and wanted to convert a 3.3 GHz signal to a 12 MHz intermediate frequency. You might think of using a mixer, but you’d need a local oscillator of nearly 3.3 GHz which is not only hard to build, but also will be very close to the signal of interest which is not a great idea. Instead, [Gregory] opted for a sampler, which uses an effect you usually try to avoid — aliasing — to allow downconversion with a much smaller local oscillator. You can see the design in the video below.
In the case of converting 3.3 GHz to 12 MHz, the local oscillator is around 100 MHz. How does that work? Watch the video and find out. The final project will triple the 3.3 GHz signal and we presume the 12 MHz downconvert is to easily phase lock the frequency using a PLL (phase-locked loop).
1985 saw the release of the Casio SK-1, a compact sampling keyboard that brought the technology to a lower price point than ever before. However, one drawback of this was that it comes stock with only a 2.5 octave keyboard. [Jonas Karlsson] wanted a little more range out of the instrument, so set about hacking in his own octave mod.
The build consists of fiddling with the SK-1’s microprocessor clock to change the pitch of the notes generated by the instrument. The original clock is generated by a simple LC circuit, which in this mod is fed to an inverter, and then a pair of flip-flops to divide the clock by four. The original clock and the divided version are then both sent to a mux chip. With the flick of the switch, either the original or downshifted clock can be sent to the microprocessor.
With the slower clock feeding the microprocessor, all the notes are downshifted an octave. The resulting sound, which you can listen to on Soundcloud, is similar to what you get when chopping down sample rates. It bears noting, however, that as this mod changes the master clock, other features such as rhythms are also effected.
Dance and house music exploded in a big way at the end of the 1980s. Typically the product of well-equipped studios with samplers and mixers worth thousands of dollars, it was difficult for the home gamer to get involved. That was, until the advent of the glorious Amiga, as [cTrix] ably demonstrates.
The video explains the history of both the music and the hardware, and highlights just why the Amiga was so special. Packing stereo audio and a four-channel sound chip, it had the grunt to pump out the tunes. All it was lacking was an audio input – which is where third-party hardware stepped in. Parallel-port analog-to-digital converters hit the market in a big way, letting users sample audio on their home computer without breaking the bank.
[cTrix] then proceeds to demonstrate how one would go about producing a dance track on an Amiga way back in 1990. A home stereo is used to play records, hooked up to a Stereo Master parallel port sampler. With a bunch of drum, piano, and synth samples recorded and saved on disk, a tracker is then used to assemble the track. It’s then compared with other music from the era as a great example of how things used to be done.
Back in the ’80s, home computers weren’t capable of much in terms of audio or multimedia as a whole. Arguably, it wasn’t until the advent of 16-bit computers such as the Amiga that musicians could make soundtrack-quality music without having to plug actual studio gear up to their machines. [Michael Wessel] is trying to bring some of that and many more features to the Amstrad CPC with his ambitious LambdaSpeak 3 project, an expansion card built completely up from scratch and jam-packed with features.
First, and likely giving it its name, is the speech synthesizer. [Michael] has made an emulation mode where his card can act just like the original SSA-1 expansion, being able to be controlled by the same software as back then. By default, the card offers this mode with an Epson S1V30120 daughterboard (which is based on DECTalk synthesis), however for further authenticity you also have the option of fitting it with an SP0256-AL2 chip, the same one used in the original Amstrad hardware in 1985.
As for the more musical part of the project, the board supports 4-channel PCM playback, much like the Amiga’s sound offering. This can be used for a drum machine sequencer program, and it has an Amdrum mode, emulating another expansion from the original Amstrad days. Sample playback can also be used alongside the speech synthesis as shown here, with random allophone beats that wouldn’t sound out of place in a Kraftwerk recording. Finally, by using the UART interface included on the LambdaSpeak, you can also turn the CPC itself into a synth by giving it MIDI in/out and interfacing a controller in real time with the computer’s AY-3-8912 sound chip.
The lengths the retrocomputing devotee must go to in order to breathe new life into old gear can border on the heroic. Tracing down long-discontinued parts, buying multiple copies of the same unit to act as organ donors for the one good machine, and when all else fails, improvising with current productions parts to get that vintage look and feel.
This LCD display backlighting fix for a vintage audio sampler falls into that last category, which was pulled off by [Inkoo Vintage Computer]. The unit in question is an Akai S1100 sampler, a classic from the late 1980s that had already been modified to replace the original floppy drive with a USB reader when the backlight on the LCD began to give out. Replacements for the original electroluminescent backlight are available, but [Inkoo] opted for a cheaper way out. An iPhone 6s 6 Plus backlight was an inexpensive option, if it could be made to fit. Luckily, [Inkoo] was able to trim the diffuser without causing any electrical issues. A boost converter was needed to run the backlight from the sampler’s 5 V DC rail, and interfacing the backlight’s flexible circuitry to the 80s-era copper wiring was a bit fussy, but the results were great. The sampler’s LCD is legible again, and looks just like it might have in the studio back when [Depeche Mode] and [Duran Duran] were using it to crank out hits.
We’re all familiar with record-your-own-message greeting cards. Generally they’re little more than a cute gimmick for a friend’s birthday, but [dögenigt] saw that these cards had more potential.
After sourcing a couple of cheap modules from eBay, the first order of business was to replace the watch batteries with a DC power supply. Following the art of circuit bending, he then set about probing contacts on the board. Looking to control the pitch of the recorded message, [dögenigt] found two pads that when touched, changed the speed of playback. Wiring these two points to the ears of a potentiometer allowed the pitch to be varied continously. Not yet satisfied, [dögenigt] wanted to enable looped playback, and found a pin that went low when the message was finished playing. Wiring this back to the play button allowed the recording to loop continuously.
[dögenigt] now has a neat little sampler on his hands for less than $10 in parts. To top it off, he housed it all in a sweet 70s intercom enclosure, using the Call button to activate recording, and even made it light sensitive with an LDR.
For those wondering why [Atarity] would go to this much trouble to test arcade buttons, we suspect an ulterior motive – skip to the 21:14 mark of the long video below to see the real design inspiration. Regardless of the motive, there’s no doubting the care that went into the build – CNC-milled birch case, extremely detailed laser-engraved graphics, and a carbon-fiber back plate covered with suede, because suede. We especially like the detail on the speaker grill: the embroidered fabric and puffed-up look really works with the rest of the design, including the leather hand strap.
It’s not entirely clear from the post what the end goal of the testing is, but we assume it’ll be some sort of MAME build. In which case, [Atarity] might want to check out our recent articles on a tabletop MAME cabinet or this portable MAME rig. But whatever he comes up with, we’re sure the craftsmanship will be there.