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Twisted Electrons Acid8 MkII

8-bit Synthesizer
Published October 2016
By Paul Nagle

Twisted Electrons Acid8 MkII

Twisted Electrons offer a new take on the classic acid machine.

Like it or not, the Roland TB303 made a significant dent in our culture, proving far more enduring than anyone — especially Roland — could ever have imagined. Clones — with and without sequencers — have been around since the 1990s, but it’s always a treat when the idea is turned on its head and nobody has to play the ‘how close is it?’ game.

Twisted Electrons have taken obvious inspiration from the ubiquitous little Bassline, but started afresh with an 8-bit oscillator spouting multiple waveforms, and a markedly different analogue filter. The layout and choice of controls are very familiar but the inclusion of DSP effects and MIDI are further hints that this is a completely new type of acid machine.

Twist Again

This is Twisted Electrons’ second version of the Acid8 and it’s a smaller, more solidly impressive creation than its predecessor. It’s now a compact 21 x 10cm and is 4.5cm tall from its cute rubber feet to the tips of its superior quality metal knobs — knobs that are securely bolted and spaced for maximum comfort across the black, brushed-aluminium panel.

If I seem on the verge of gushing, I must apologise; it’s just that such attention to detail is rare and deserves credit, especially when it’s from a small company. The scaling down does have one drawback though: all the rear connections are on 3.5mm jacks, even the MIDI In and Out ports. Two adaptor cables are supplied (each 134cm long) and should you ever misplace one, they are wired to the same ‘standard’ as the adaptors for Korg’s latest Electribes. Sync jacks (In and Out) expect and deliver 5V pulses suitable for connection to most analogue gear (it also coped with the 12V output of my Arturia Beatstep Pro). Audio is a single mini-jack and there’s no headphone socket, on/off switch or battery option. An external power adaptor is supplied but the manual suggests it can be powered by any AC or DC voltage source of between 7V and 15V, 1200mA.

Apparently, the MkII version features a stronger accent than the original, but otherwise the circuitry, layout and firmware are all the same. On both models, white LEDs are used throughout for status and sequencing; and, unusually, you can set them to be much brighter than normal using a power-on option. It could be a lifesaver in that daytime festival slot!

Pieces Of 8

A single encoder toggles between pattern selection and step-edit modes, and in order to audition the 8-bit waves, you’ll need to pick the latter. There are a total of 16 waveforms divided into categories printed beneath the first four white keys, ie. rectangle (square to you and me), triangle, sawtooth and sine. Within each category are variations, their names listed in the manual but the inspirations clear. The rectangle category, for example, features waves called Prophet, Distorted, SID and ‘perfect’ Square. SID waves appear in the triangle and sawtooth categories too and there’s a TB303 saw, more Prophets and a couple of 3-bit waveforms. The last wave in each group can be replaced with something original — once you install some freebie software.

Repeatedly pressing the waveform button cycles through the variations, with LEDs on steps 5-8 showing which is chosen. Impressively, you get to decide whether each pattern remembers the waveform choice or whether the selection is global. The value of this shouldn’t be underestimated — it’s particularly cool when you start making variations of patterns and chaining them together.

The observant are probably wondering how many variations of a sine wave there can be. In this case, the first version is pure enough but the second gains a high harmonic that implies an octave of upwards shift. The last pair of ‘sines’ are really nothing of the sort: the first is ‘acoustic guitar’ and the last ‘piano’. These may seem like random choices but they’re a welcome step up in complexity over typical subtractive waves, and a nice hint of the potential of user waves. Some variations are quite subtle (although the differences invariably show up in the lower regions); the Prophet triangle, for example, has a hollow quality compared to the buzzy, aliased SID version. Even when waves are audibly similar, they’re easily separated by the Acid8’s digital and analogue processing. At this stage I had yet to draw any waveforms myself, keeping that particular treat until I’d played with everything else.

Turning next to the filter, it’s quite unusual, but familiar if you’ve ever played with the crunchy Meeblib Anode. This is the same Texas Instruments band-pass design that is persuaded to behave (almost) like a low-pass filter. Primitive it may be, but the scratchy, rough-edged tones are a perfect foil for the 8-bit oscillator, and the resonant whistle is very distinctive indeed. Accent, at its maximum, drives the filter hard and with moderate to high resonance delivers a deliciously biting fizz.

In perhaps the least welcome departure from the attributes of a 303, the decay is quite linear, which has a major impact on the feel and sound of every pattern. I realise the ‘perfect’ envelope shape is a matter of personal taste, so all I’ll say is that I prefer a more traditional exponential curve and the range of zappy twangs that go with it. Here, the shortest decays suffer the most, but on the plus side, long decays yield a new breed of crunchy sub-basses. One of my favourite settings involves the Prophet triangle wave, low values for cutoff and resonance, high accent and just a smidgen of filter modulation. Add an occasional slide between notes then sit back and grin — unless you have a heart of stone!

The rear panel accommodates connections for MIDI I/O, audio out and sync on 3.5mm jack sockets. The rear panel accommodates connections for MIDI I/O, audio out and sync on 3.5mm jack sockets.

Decay preferences aside, the controls operate as you’d hope and expect from a machine laid out to match a TB303, with one exception: there’s no tune control. In its place is the ‘FX’ knob, although turning it might not immediately blow you away. That’s because the knob doesn’t do anything until you activate at least one effect. These are named above the five ‘black notes’: Scrub, Acc, Crush, PW and Arp.

These effects are beautifully consistent with 8-bit audio, although beautiful doesn’t describe any of them. The first isn’t even an effect as such; Scrub holds the sequencer at a single step that corresponds to the position of the FX knob. It’s a slick tool for slipping in pattern variations, made better by the fact that the Acid8 tracks where the pattern would have progressed to. Turn the effect off and it leaps to the right place — nice!

The next effect toggles accent on and off, the toggling rate set by the FX knob. It’s quite independent of the tempo but with it you can morph from a fast glitchy effect that flips the accent multiple times on a single note to a more sedate, occasional accent. At slower rates this introduces a semi-random feel to the filter burbling, becoming an instant firm favourite.

Crush supplies two functions for the price of one: sample-rate and bit-rate reduction. What you get depends on the direction of the FX knob from its central position. The 8-bit waveforms are already imperfect but with a touch of Crush you can subject them to a world of pain. The control magnifies any differences between waveforms and puts the Acid8 in a class of its own — probably spitting and clawing at the blackboard.

Pulse Width varies the width of all waveforms, not just the rectangular types. At the thinnest settings the output almost disappears so the thinning process can give the impression of more than just a single filter mode.

Another ‘FX’ option that’s arguably not a genuine effect is the Arpeggiator, which slots new notes in between those already present. It’s therefore not a regular arpeggiator either, but the splurges of madness it brings should raise a few smiles, along with memories of early arcade games. The further you turn the FX knob, the more notes you get and the higher they are.

Apart from the restriction of the single FX knob, there’s no limit to the number of simultaneous effects, and some pair up quite magically. Crush and Pulse Width, for example, can flesh out then totally dismantle a waveform. At the extremes, all you’re left with is often something broken-sounding, crackly but absolutely unexpected.

That’s the end of the FX but there are still a couple of sonic manglers left. The first is ‘bit flipping’ and its effects are felt the most dramatically when applied to purer waveforms such as sine and triangle. All the bits of the datastream can be individually inverted so you can choose subtlety or full-on gritty brutality. Bit flipping is global and it’s another process that puts the differences between waveforms into stark relief.

A fascinating bonus feature is so simple you could miss it: a switch that connects the modulation envelope to oscillator pitch. The connection made, the Acid8 is capable of freakish percussion, mournful pitch sweeps or full-on Nintendo nostalgia. Pitch modulation status is stored in each pattern.

The free pattern editor allows you to view and edit patterns.The free pattern editor allows you to view and edit patterns.

Sweet 16

The sequencer follows the well-trodden format of patterns up to 16 steps long. There’s a pool of 128 to draw from and patterns can be chained together to form basic songs. It’s a winning formula if you ask me!

When in Pattern mode, a new bank is chosen using the white keys and patterns within the bank are selected with the encoder. You never have to worry about saving them because this happens automatically. Copying and pasting is implemented with no requirement to stop the music. You do, however, have to select the new pattern before you can paste, so it’s not perfectly seamless (which you might have preferred if you’re partial to developing patterns live).

It’s important to know which mode you’re in so you don’t accidentally transpose a pattern when expecting to swap waves, but that’s about as badly as you’re likely to cock up. Flip into step mode and the encoder selects the step to edit. Via the small keys you can add notes, rests, accents and slides to taste, as well as octave transpositions. It’s also a user choice whether or not to automatically advance the sequencer as each note is entered.

Real-time recording is also possible. It involves the slightly awkward shift/encoder/run combination, which I had initial difficulties with. When externally MIDI-synced, I invariably slipped out of sync or changed direction. With user error a distinct possibility, I nevertheless mentioned this in an email alongside a couple of minor bugs and a suggestion. Within a few days, updated firmware dropped into my mailbox addressing the lot — including my combo conundrum. I’d almost forgotten that companies could work so fast!

I mentioned changing directions just now and it’s one of several options that distance the Acid8’s sequencer from many in its class. Even some otherwise advanced machines have no concept of reverse, pendulum and random, all of which are available to the Acid8. Patterns can be shortened too, by skipping steps. To skip multiple steps in a single operation, there’s a three-way combination that feels surprisingly natural: shift, skip and a spin of the encoder. Swing is offered too, with eight progressively swingier levels.

During playback, you can add performance effects that remain active only as long as you’re holding the grey FX keys. Other non-destructive overrides include the insertion of rests, accents and slides — and transposition. A simple key combination clears the pattern entirely and with an extra button press you can generate a completely new random pattern, always a popular parlour trick of the TB303. Naturally you can keep doing this until you generate something worth claiming.

Finally, up to eight patterns can be chained to run in succession and five separate chains are maintained. Other than observing that you can include the same pattern multiple times, that really wraps it up for chaining — it just works.

MIDI & Sync

The Acid8 will be your master clock if necessary, the tempo set by tapping the button or by holding it and turning the encoder. Alternatively, via one of the supplied cables, you can sync to incoming MIDI Clock. If analogue is more your cup of tea, the sequencer will advance for each 5V pulse received at the sync input and will spit out 5V clock pulses from the sync out jack.

As the sequencer transmits its notes from the MIDI output, I simply had to try it out with my rackmounted MAM MB33 II. Ordinarily, you’d expect slide to be transmitted as overlapping (legato) notes, but initially this was not the case. Happily, one timely firmware update later and it now works beautifully! Notes are sent at velocities of 64 or 128 for accented notes.

Should you require it, the MIDI output can provide thru functionality. Incoming MIDI is basic but functional. Program changes are routed to pattern selection and the mod wheel controls the FX level, but otherwise, only notes are recognised. (The pitch tracks accurately for approximately three octaves). You can define the MIDI in and out channels separately but channel 16 is reserved for the software editor.

Conclusion

The Acid8 should appeal to anyone who values synthesis without fuss, and sequencing according to old school rules. True, it matches the layout and general appeal of the TB303, but the concept has been thoroughly reworked in favour of a fresh new sound. The finish is superb and those knobs are a lesson in how reduced size and high quality need not be mutually exclusive. I found the 8-bit oscillator’s ever-changing waveforms a treat, especially when you start flipping bits, varying the pulse width or reducing the sample rate. The inclusion of user waves is no gimmick either and the editor’s graphical pattern overview could be handy too — and even more so if some form of backup were implemented.

There should be ample patterns for most purposes and the chaining method of linking them together is fast and painless. Possibly the star of the show is the dirty, fuzzy filter, a welcome change from... pretty much everything! Add random accents and a squeaky dose of resonance and you won’t go far wrong. Performance is surprisingly well catered for too, with options for pseudo-fills, chiptune simulations and many types of temporary override. And if your ideas still aren’t flowing as well as you’d like, the randomiser is on hand to inject its own form of creative lubricant.

For me, only the choice of linear decay was a let-down — your mileage may vary. It would also, arguably, have benefited from a tune control, but those considerations aside, the Acid8 feels complete and ready to rock. It’s tweakable, temptingly-priced, neat, petite and different. It deserves to do well.

Alternatives

The Meeblip Anode combined with a step sequencer would probably be the closest alternative. Or — if you can find one — the Oto Machines Biscuit with its ‘Der Oto’ synth personality loaded.

Wave Hello

Drawing your own waveforms can be a  somewhat crude process. Drawing your own waveforms can be a somewhat crude process. Treat yourself to a visit to the Twisted Electrons web site to gain the latest firmware and a free waveform/pattern editor. It’s only at version 1.0 right now, but it behaved solidly within its remit. I had to install Java first on my Windows 10 laptop, but it worked straight away on my Mac.

You’ll also need a regular MIDI interface and two-way communication with it, because the Acid8 has no USB port. Any extra effort this entails is well worth it, whether or not you care about browsing or editing patterns graphically. The editor is helpful in clarifying those elements that are specific to a pattern and those that are global. It only really falls short by failing to offer a ‘pattern save’ option.

Probably the main reason for installing the editor is to create original waveforms. Admittedly, producing smooth curves would take better mouse control than I possess (even straight lines were a challenge), but regardless, drawing waveforms is fab and endlessly diverting! As you draw, the data is sent straight to the synth, giving constant invaluable feedback. And any time you decide your work is not an improvement on the original, you can restore the factory waveforms with a click.

Published October 2016