Review: Doepfer A-111-6 Mini Synth

When Doepfer announced their new A-111-6 synth voice at Superbooth 2019, it immediately grabbed my attention. Not because Doepfer did a synth voice module – they had in the past already done the A-111-5, essentially a first-generation Dark Energy in module format. Not because of its radical feature set – at least at first sight, the combo of oscillator+sub, one envelope and 4-pole lowpass filter doesn’t raise any eyebrows. However, the combo of a 10TE width and €180 price was a statement. I’ve already discussed this before: other synth voices (analogue ones specifically) are considerably larger if they have a comparable feature set, and are always more expensive.

But, is it any good?

Mechanical

Design-wise, this module is in the vein of the newer slim-line modules by Doepfer: compared to their standard modules, this leads to smaller, rubberized knobs, and smaller, more closely packed jacks. While this is definitely a move to the smaller side, I found other modules from that series (e.g. the A-140-2 dual envelope) perfectly easy to handle, and in that regard definitely better than products by e.g. 2hp or Erica Synth’s Pico series.

The bottom of the module holds a total of ten jacks (eight inputs and two outputs, for audio out and envelope CV). On top of that, there’s rows of five knobs, five switches and five knobs again for the module’s functional blocks of VCO (three knobs and switches), VCF (three knobs) VCA and envelope (two knobs and one switch each).

Under the hood (or rather, on the module’s PCBs), you can find a total of nine jumpers and six trimmers (although some of the trimmers are not considered user-servicable parts).

And yep, all that power goes into a mere 10TE, albeit with a depth specified as 50.5mm. Which means you’ll have a hard time with a lot of super-slim skiff cases (e.g. Frapp Plus, Intellijel Palette), and also Behringer’s first-generation cases. However, everything that’s a little bigger (including Tiptop’s Mantis, everything by Doepfer and even the small NiftyCase) works fine.

Considering the Moog cases are specified at 1.9in, which converts to 48.26mm, it should not fit. However, a quick test showed that yes, this module does fit into the Moog case.

Functions

VCO

A standard triangle-core VCO with square/pulse and a choice of triangle/saw. As the A-111-5 was a module version of the Dark Energy, one might assume that this device is a module version of the Dark Energy III – and part of the specs and features do suggest this.

There’s no mixer for the waveforms; one switch is used to choose between triangle/saw/off, the pulse/square is turned off by setting the pulse width to zero or 100%.

The frequency is set with a 3-position octave switch and a tune knob which can be set to span either +/-0.5 or +/-2 octaves with a jumper. Apropos frequency: the range is 32Hz-16kHz (i.e. nine octaves), which is quite a lot in the high register.

The VCO is controlled with two input jacks – next to the 1V/Oct pitch control, there’s a Mod input that can be set to pulse width, frequency (i.e. linear FM) or nothing via another 3-position switch, and gets its dedicated attenuator knob. It also receives pitch control from the bus if the corresponding jumper is set.

Finally, there’s a suboctave waveform which runs one octave below and produces a square wave.

Looking at the oscillator properties, the triangle looks relatively good waveform-wise, but shows some underbelly in the waves. Odd harmonics are down ca. -60dB i.e. fairly inaudible, the fact that there’s also a subharmonic suggests that this is the sub oscillator leaking through.

Triangle Wave Triangle Spectrum

The square/pulse wave looks pretty nice as well, especially with rise/fall times of ca. 20us.

Square Wave Square Spectrum

Finally, the saw has the usual triangle-core problem of a dip in the middle of the rising portion of the waveform.

Saw Wave Saw Spectrum

All in all, while we’re definitely not looking at a “best in class” oscillator, it looks (and sounds) just fine.

Mixer

As already stated, the main waveforms don’t have a proper mixer but rather are switched between or, in the case of the square/pulse width, can’t really be controlled in level. For the relationship between those waveforms and the external in (or suboscillator), there’s both a dedicated knob (Balance) and a CV input which fades between them as an offset to the balance knob. With that, pretty interesting things are possible especially when feeding an external signal (such as another oscillator) into the external in, and this is a feature not often seen on (modular) synths.

Filter

A 24dB/oct lowpass filter for which we don’t get any additional info. It’s obviously not the same one as in the Dark Energy III, though, as that one uses a 12dB/oct one.

There’s knobs for frequency and resonance, and two inputs for frequency control, one of them with an attenuator knob, which is normalled to the envelope. The second frequency input can be normalled to the bus (for filter tracking) and for that reason is calibrated to be close to 1V/Oct.

My first impression was that it’s a flexible, but rather bland and not at all punchy filter. Diving deeper, it becomes clear that it is one of the designs were the passband is attenuated as you turn up resonance – and plots (with the filter fed with white noise from a Disting) confirms that: the lower part of the passband (ca. 2 octaves down from cutoff) is down ca. 8dB starting at resonance at “2” (i.e. already where you can’t even properly hear the resonance). The filter also starts to sing pretty clearly with the resonance knob set at 12 o’clock (“5”).

Flt 0 2 5.png
Filter spectrum fed by white noise for frequency at “5” and resonance at “0” (purple), 2 (red) and 5 (orange).

Once we reach higher resonance settings, something starts to distort. It’s not the audio interface, it might be the VCA’s input, or it might be the filter itself.

Flt 0 8 10.png
Distortion happens at resonance of “8” (red) and “10” (orange). Resonance at “0” (purple) plotted again for comparison.

This is obviously a combo of gain staging and filter design decisions, but in my opinion these weren’t wise decisions. Resonance above 5 or so is pretty useless (unless a distorted sine wave is what you’re looking for), and the passband attenuation doesn’ make it a really sensible choice for bass synth application with “squelch”. There’s no sensible way to drive it so hard from the input that it slowly stops resonating, and speaking of resonance, turning that up also pulls cutoff downwards from onset of oscillation to fully cranked by about a major third.

VCA

There’s three VCAs in this synth (two of them in the mixer section, which were already discussed there). This section is about the main VCA before the output jack – the standard amplifier section of any synth.

Doepfer points out that this design has an unusual characteristic, going exponentially to about -20dB (question to Doepfer: related to what?) and then continuing in a linear fashion up to full level. While I didn’t run any analytical tests, this seems to sound fine without giving you a “better than everything else” experience – but looking at how both the human perception and synths work, this might be a very sensible choice.

The VCA is controlled by gate, the envelope or nothing at all. For “nothing” to make sense, there’s also a bias knob for all the drone synth folks.

To avoid ugly clicks when controlling the VCA with the gate signal, there’s a slew option (which can be configured with a jumper) which takes care of that potential issue.

What this section doesn’t have is a CV in, meaning you can control the VCA with the integrated (and somewhat limited) envelope, or with an on/off signal, but not with a full-fledged external envelope. Pity.

There’s a workaround of sorts, though: If set to “Gate”, the VCA is controlled by the signal connected to the module’s gate jack. That means that by connecting an envelope there, the VCA gets controlled by this envelope. The downside: the A-111-6’s internal envelope then receives its gate information from that envelope as well, and for some reason, it refrains from working properly in its AD mode.

Another workaround is to use an external VCA – this is easily accomplished by setting the aforementioned switch to “off” and turning the gain knob all the way up.

Envelope

This is perhaps the oddest component of this synth. An envelope that is both really weak and really powerful.

On the weak side, it’s got two knobs, one for attack and one for decay/release. There’s three modes: AD (where it treats the gate as a trigger), AR (with sustain at 100%) and ADSR (with sustain set to a fixed 50%). In consequence, there’s no way to set sustain, and I don’t like that.

On the strong side, it’s got CV control over time, with two jumpers separately configuring it in polarity for attack and decay/release. Also on the strong side is a range of 1ms…5s for attack and 1ms…15s (which according to the manual can be considerably increased via CV control). This is definitely beyond the range of your usual monosynth voice.

There is another observation which I at first would have placed in the filter section and that is that if resonance is audibly up (i.e. around 5 or higher) and the filter gets modulated by the internal envelope you get some ugly, distorted noise. I could rule out the filter circuit itself or the filter under modulation as the culprit by trying the same with another envelope, so it seems to be a problem of the envelope – which I couldn’t confirm with it controlling the VCA, at least not by ear. Still, it’s not nice.

Under the Hood

With its nine jumpers and six trimmers, the A-111-6 offers quite a few configuration and calibration option for those that are happy to work that way (but hey, that’s practically everyone in the modular world).

A total of four trimmers is used for calibrating VCO and VCF frequency offset and scale and should, under normal conditions, never be touched (with the exception of the VCF scale if you want the filter to over- or undertrack).

The remaining two trimmers adjust the offset for the octave switch for the VCO, i.e. to adjust if -1 or +1 octave is really that (or, again, something different if you’re using a Bohlen-Pierce scale).

One jumper sets if the pitch jack is routed to the filter (i.e. if you want the filter to track this jack), and a total of three jumpers sets if the bus affects VCO, VCF and gate, respectively.

Note: If the bus is not used in your system, i.e. if no source feeds it, the bus acts as an antenna of sorts, which can easily disturb your pitch if the VCO is set up to react to bus pitch. If you don’t know what I’m talking about: best remove all three jumpers on the bottom right of the module. Best check on all other Doepfer VCOs you have if that is set correctly as well.

A further two jumpers set if the CVT jack affects attack and/or decay/release times and if so, if positive CV will increase or decrease the time.

The remaining jumper is to set gate slew to on or off.

In Use

I acquired the A-111-6 to go into the NiftyCase as part of the Growing Smaller setup, and that’s where it’s been since. This setup consists at this point in time mainly of two synth voices – the other one assembled from a Chipz oscillator/LFO combo, and VCA, filter and envelope by 2hp. There’s also two sequencers – Cellz and Bloom, and there’s also a keyboard synth (Bass Station II) and a groovebox with the MC-707.

The first thing I noticed is that compared to not only modular and semi-modular alternatives, but to other synths in general, this one is really easy and quick to set up for a given patch. The limited connectivity options here actually help – for any given sensible patch, you’re done in about a minute.

Considering what you can do with it, it’s pretty much what you expect: a generic synth voice without any specific colour, and thus not locked into one application but rather bland in most any scenario. With the sonic properties of both oscillator and filter section, it works well both in bass patches without filter resonance, and also in synth leads with a somewhat wind instrument (including french horn) character.

I consider the lack of adjustable sustain on the envelope its main weakness, and as such, it works best controlled by a step sequencer which sends triggers.

From its sonic character, it does complement the Bass Station II well, as that one has more of an angry/edgy sound. So in that specific setup, it works as a good companion for everything where you need two contrasting monosynth voices.

Apart from its use as a full-blown synth voice, its ease of use can also make it a nice tool when starting to set up an arrangement, where you can just connect it with three cables for that voice where you’ll be working on a complex patch later, and the combo of small form factor and low price helps in that application, too.

Baffling Design Choices

When we reflect on some of the design choices and trades made by the design team, we need to understand what this is (or could) be good for.

First and foremost, it’s a basic analogue mono synth voice, and minimum options for that would be oscillator, filter, VCA and at least one envelope normalled to the VCA, plus envelope control for the filter. We get that. We even get a sub-oscillator, and three waveforms for the oscillator.

In addition, we get CV control of the oscillator/sub blend, two filter CV inputs for the filter, and CV control of envelope time. What we don’t get, however, is CV control for the VCA (other than by the internal envelope), and sustain level control for the envelope.

To me, a CV input for the VCA or a sustain parameter for the envelope would have been preferable choices. I’d happily sacrifice the second filter frequency in, the CVT in and even the sub blend to get it. And while we’re at it, I’d also happily donate either the Gain knob or the Mod knob to get a Sustain knob. I really don’t get those choices, and Doepfer would have had the opportunity to make all of that happen. Note that the Dark Energy III does have all of these features and no, it’s not really a space issue.

Summary

Once again, there’s a module that leaves me with really mixed feelings.

Starting with the hard facts, there’s nothing to argue: regarding features per cost and per size, this one is without competition.

In addition, some of the features are welcome surprises, such as the balance dual VCA or the CVT control for the envelope.

On the other hand, some design choices appear somewhat surprising, and can’t be justified with price or size. Rather, these were trades made by the design team, and in my opinion could have been made better (but as they say, your mileage may vary).

As for indisputable deficits, there’s the noise induced by the envelope when modulating the filter: this is a serious drawback.

It’s also necessary to point out that this is – due to its size restrictions – different from most other semi-modular synths insofar that interfacing with other modules (such as using the module’s features together with other modules or vice versa) is limited due to the small number of connectors.

Then again, as a basic monosynth with some added features, it delivers. Period.

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