A-190-5 Polyphonic USB/Midi-to-CV/Gate Interface

The A-190-5 is a Midi-to-CV/Gate interface primarily intended for polyphonic applications. This means that up to four modular synthesizer voices can be controlled via any midi keyboard.

Polyphony is still a rather exotic “fringe phenomenon” in the modular area. Effort, cost and complexity to control such a system appear relatively high compared to modern analog or virtual-analog polysynths. Nevertheless, there is a lot going on here that I personally think is extremely exciting.

The interface has Midi-In and Midi-Thru, can also be addressed via USB and allows the control of up to four analog synthesizer voices with gate, CV for pitch and velocity, as well as configurable CV outputs for modulation signals.

User interface







The thing with the USB port

Doepfer points out on its website that using the USB port, e.g. as an interface to a DAW, can cause problems. The reason is that all Midi signals that are sent to the module via the DIN Midi input or via the USB port are also output via Midi Thru to this USB port.

So every note that you send from the DAW to the module, it sends back immediately. If the DAW track that controls the A-190-5 interface also accepts all Midi inputs connected to the DAW, then a loop and the corresponding “Midi data salad” occur.

However, the solution to the problem is quite simple: you just have to make sure that the DAW track for the A-190-5 does not accept midi signals from this very module. For example, “All Midi Inputs” is not a good idea for this track. Some DAWs also offer the ability to block certain Midi/USB inputs entirely, which is also an option.

Connection possibilities via the board

In contrast to many other more recent Doepfer modules, there are no configuration options on the boards. But there are two pin strips for the output gate signals and “CV Note” – control voltages. Small cables fit on it (look for “jumper cables” at electronics stores) via which you can connect the interface to the polyphonic VCO A-111-4 or the polyphonic ADSR A-141-4 (from version 2, with the first version you still have to solder).

The connectors JP8 and JP9 for Gate and Note CV. The other jumpers do not contain any user options.

Operating modes at a glance

The “+” and “-” buttons can be used to switch between the six operating modes of the interface. The differences lie in the number of midi channels to which the module reacts and in how many simultaneous notes per midi channel are converted into the modular world of CV and gates.

Operating mode:Midi
Behavior of the analog outputs:
11Monophonic on all four outputs simultaneously, all outputs play (unison) the same notes.
All in all, a single modular voice (issued four times).
21Outputs 1+2 play (unison) the notes of the first midi channel, outputs 3+4 (unison) the notes of the second midi channel.
In total two modular voices (each issued twice).
41Quadruple monophonic, each monophonic output plays the notes of the corresponding midi channel set in the interface.
In total four modular voices.
14Four-part polyphony, overlapping notes are assigned to the next (free) output.
In total four modular voices.
12Two-part polyphony, the notes played are assigned to outputs 1+2 (unison) and 3+4 (unison) in rotation.
In total two modular voices (each issued twice).
22Two-voice polyphony with two midi channels, outputs 1 and 2 are assigned the notes of the first midi channel in rotation, outputs 3 and 4 are assigned the notes of the second midi channel in rotation.
A total of four modular voices.

Programming the options

If you press the “Enter” key in one of the six operating modes, you get to the edit menu of the interface. You can switch between the options with the “+” and “-” buttons, the values for the individual options are set by pressing “Enter” and then the “+” / “-” buttons.

RetriggerTime from 0 to 50 milliseconds. At 0 ms, no new trigger/gate is output on the corresponding analog output when playing legato.
MidichannelThe Midi channel whose notes the module converts into analog gates and control voltages (channel 1 to 16). In the operating modes for several Midi channels, the channels are set one after the other and each completed with “Enter”, then the next channel selection follows.
RefnoteThe midi reference note for which the interface outputs 0 V as control voltage at output CV1. This is the lowest midi note the module responds to. In the operating modes for several midi channels, the reference notes for each midi channel are set one after the other and completed with “Enter”, then the reference note for the next midi channel follows.
The value range of this lowest midi note is midi note #24 to #96, which corresponds to C0 to C6.
CV3The midi controllers that are output on the four “CV3” outputs. Doepfer has thought very cleverly here and made a separate Midi controller possible for each of the four “CV3” outputs: Controllers such as monophonic aftertouch, modulation wheel or sustain pedal are not generated per note, but per Midi channel. Especially in quadruple poly mode, you can use four different controllers for expressive play with the A-100. The controllers are set for each of the four “CV3” outputs one after the other and the programming is completed with “Enter”, then the midi controller follows for the next “CV3” output.

Retriggering in practice:

What does setting a retrigger time mean in practice? Basically, the interface will output a gate signal at the “Gate” output with every new note. Since gate signals are always output as long as the key is pressed, the generated gate signals of the corresponding analog output overlap when playing legato in “Mono” or “Unisono” modes and the envelope curve is not restarted.

To force a restart of the envelope, you can now set a time from 1-50 ms in which the gate signal is interrupted as soon as the new key is pressed. Here you have to try a little: Too short pauses may not restart the envelope, too long pauses may be heard as a slight delay with percussive envelopes.

If the retrigger time is set to 0 ms, the gate signal is not interrupted when playing legato and the envelope is not restarted in this case. This is actually the standard behavior of classic (monophonic) analog synthesizers.

I could not determine any effects of the retrigger times in the poly operating modes – here the next analog voice takes over with its own gate signal. When the voices “overflow” after the fourth analog voice, the first “CV Note” output again emits a new control voltage, but the first “Gate” output does not interrupt its gate signal to restart it.

Refnote in practice:

For most keyboards, C0 (midi note #24) is sufficient as the lowest possible note, but on an 88-key keyboard like my LMK2, for example, the keyboard extends a little further down to A-1 (that’s the midi note #21). So that the bottom three keys do not remain unused, you can transpose the keyboard up 1 octave if necessary to use the full range. In terms of the interface, there are hardly any upper limits to the pitch range with its control voltage of up to 10 volts (= 10 octaves at 1V/octave!).

Control voltages up to 10 volts:

The A-190-5 interface delivers a potent 10V maximum control voltage. That’s quite a lot for some of the “normal” (non-polyphonic) modules, e.g. an A-140 only delivers up to 8V, LFOs usually up to 5V (or sometimes +/- 2.5V). Of course you can’t break anything with it, but you should turn down the attenuators of filters etc., which are controlled by the A-190-5, a little further in comparison to get meaningful control ranges. Incidentally, the polyphonic modules A-141-4 VC ADSR and A-132-8 Octal Poly VCA are also designed for +10 V control voltages.

Limitations and possible further developments:

The interface currently (June 2021) still has the very first software version. Normally, Doepfer continues to refine its digitally controlled modules, so we can hope for future features here.

Many monophonic midi-to-CV interfaces offer small “helper functions” such as digitally generated LFOs, portamento (individually adjustable for each output) or the conversion of the midi pitch wheel into the control voltage for the VCOs. This would also be very useful for polyphonic use.

There are also useful options when converting the individual notes to the CV outputs: A real “round robin”, which actually switches to the next CV/gate output with every new midi note, would let every (even briefly played) note fade away while the next note is played. Or a purely random assignment of the analog outputs per midi note, e.g. if you use four different filters or different waveforms of the VCOs. The next available analog output is currently used for overlapping notes, so a monophonic – not played legato – melody always ends up on the first analog output.

What I actually really missed is the implementation of the midi pitch bend wheel in the interface (or I was just too stupid to find it). In contrast to the modulation wheel and monophonic aftertouch, the pitch bend wheel is not a “Midi controller” with values between 0 and 127, but is made up of two bytes (that’s 14 bits in the Midi world) that correspond to a total of 16.383 possible values. An implementation would ideally affect the “CV Note” outputs directly or be output via one of the “CV3” outputs. Until the option is available in the A-190-5, you can use an additional A-190-3 interface and its dedicated “CV Pitch” output.

Let’s wait and see, Doepfer is quite creative (and productive!), but at its core a relatively small company with limited resources that has to take care of a very large number of modules.

A word (or two) about the polyphonic A-100 modules

Polyphonic modules are a challenge. Where else a simple potentiometer – i.e. a manually adjustable resistor – takes over the regulation of a control voltage, with polyphonic modules this has to be done, e.g. via several integrated VCAs, which are then controlled again via a voltage and said potentiometer. This costs money due to the additional components and it entails effort in the coordination of the module, since the (four) sub-modules should react as similarly as possible.

As the only manufacturer I know, Doepfer offers a whole range of modules that are suitable for polyphonic use: A quadruple VCO A-111-4, a quadruple filter A-105-4, a quadruple ADSR A-141-4 (which of course is basically a quad VCADSR), and finally a quadruple, no eight-fold VCA A-132-8. A lot can be done with this, while the space requirement remains manageable: Filter, ADSR and VCA are each only 8 HP wide “Slim Line” modules. Quadruple LFOs have been around for a long time anyway. And in terms of modularity, of course, we move well beyond the “standard polysynths”, after all you have a modular system.

What I would wish for in future developments would definitely be an 8-into-4 mixer, or even better 16-into-4 mixer – with common controls for the 4 output channels to use more than one VCO per voice. And maybe a few small auxiliary modules, such as a quadruple waveshaper, a quadruple slew limiter with a catch-up amplifier (or even a polyphonic portamento option in the A-190-5) or a simple quadruple suboscillator.

And yes, one could wish for many more polyphonic filters. In fact, I personally find the filters to be the least problematic modules for polyphonic applications. The Doepfer filters are almost all quite inexpensive and a tuning of several filters is done quickly. Then another free CV input for joint control of the corner frequency and everything is fine. If it should still be a polyphonic filter module, I would personally prefer a slightly slimmed down Xpander filter with as many of the 12 dB and – even better – 6 dB filter modes as possible.

Basic equipment for polyphony

The basis for a polyphonic modular system is actually the midi interface A-190-5. Everything else (A-111-4, A-105-4, A-141-4, A-132-8) is extremely practical and noticeably facilitates operation when playing the system. However, if necessary, this can be replaced by a series of individual modules, which then have to be adjusted to each other “by hand”.

A minimalist polyphonic system could also consist of one A-190-5 and four A-111-6 Miniature Synthesizer Voices. And why not? With the Oberheim Four Voice, you also had to set each voice manually.

Sound examples

For a first test setup, I used modules that were already in my rack. My A-110-1 VCOs were the basis (flanked by an almost identical sounding A-110-2). The choice for the filter was quickly made, as a “BBD supplement” (see posting on the A-188-1) there are six A-108 in my rack (particularly suitable for the BBDs due to the 48dB slope). I simply hadn’t “collected” enough other filters.

As a VCA, I initially thought of the A-132-4 Quad Exponential VCA, but due to the lack of a CV attenuator, it could not be used without distortion with the 10 V output voltage of the A-141-4 ADSR. Four A-140‘s instead would be feasible, but much more cumbersome than the polyphonic ADSR generator. So I combined the A-135-2 linear VC mixer with the A-141-4 and everything was fine.

The A-190-5’s “Gate” outputs trigger the four envelopes of the A-141-4. These envelopes simultaneously control the A-135-2 VC Mixer and the four A-108 filters (patched using the very handy “Stackables”).

The A-190-5’s “CV Note” outputs each go into an A-185-2 Precision CV Adder (which you can NEVER have enough of, by the way). Each A-185-2 is connected to two A-110-1 VCOs (one voice with one A-110-1 and one A-110-2). The first VCO per voice is a pulse width modulated square (modulation by four LFOs in the A-143-3), the second VCO is a sawtooth one octave above. How to mix the VCO’s? Unfortunately there is no “polyphonic mixer” yet, so I used an A-138e quad crossfader for it. Its four outputs go into the four A-108 filters.

In addition to the envelope curves, the A-190-5’s “CV2” output (= velocity dynamics of the Midi notes played) controls the cut-off frequency of the A-108 filters via their third CV input. I would have liked to have influenced the volume with the velocity too, but that will have to wait until I have an A-132-8 Octal Polyphonic VCA.

As a “special request” I had a polyphonic portamento in mind. Unfortunately, the interface does not support this at the moment, and there is also no quadruple slew limiter. But wait – it already exists: The A-129 / 3 together with the A-129 / 4 from the vocoder subsystem, which unfortunately has since been discontinued.

The modulation wheel of my LMK2 is connected to one of the “CV3” outputs and simultaneously controls the frequency and amplitude (via an A-132-4 VCA) of an A-143-4 Quad VCO/VCLFO. The sostenuto pedal (the left pedal) on the LMK2 is also routed to one of the “CV3” outputs and reduces portamento through the A-129 / 4. Finally, the monophonic aftertouch ends up on “CV3” and is patched from there to the four free control voltage inputs of the A-108 filters.

All in all, one or the other module is built in, but it is actually tremendous fun to play the A-100 system polyphonically.

In the first sound example, I use “Poly” mode, slow attack and release times and the “6dB” outputs of the ladder filters. Here, as in the second sound example, the four voices are distributed in the stereo image and provided with a VirSyn VTape delay and a Valhalla reverb in the DAW.

Polyphonic play-around.

The second sound example uses the “Unisono” mode, the envelope is set to very short attack and release times, I use the 24dB outputs of the ladder filter with a significantly higher resonance. Here too, the individual voices are distributed in the stereo image and “spiced up” with VTape and Valhalla.

Monophoic play-around.

Technical specifications

Width16 HP
Depth55 mm
Power requirements120 mA (+12V) / -40 mA (-12V)