L-1 modules

l-1_logoBelarusian electronics designer Alexey Laman manufactures Eurorack modules under L-1 trademark. His modules are highlighted both by himself and by community members as top-quality modules comparable to Cwejman products. The Company is founded in 2012. Today’s model range includes several dynamic effects (compressor, VCA, mixers), VCF and even vocoder! Modules can be purchased as fully-assembled units or as DIY-kits. In this review I’m going to introduce three L-1 modules at once: 2180VCF, Quad VCA/Mixer and Tube VCA.

L-1 modules

Alexey Laman follows few strict principles of the module design: similar hardware components, placing all sockets within bottom side of the modules, color coding for inputs/outputs and also very smart solution: use SMD-parts for all non-critical circuitry and use thru-hole critical components such as chips, timing c aps, etc. It helps to reduce soldering time seriously.

The quality of used components is important part of the design. Laman uses only 1% resistors, polymer dielectric caps, high-quality chips, high-quality pots, switches, etc. The temperature compensation widely used in the circuits and costs of the TempCo options are very reasonable, probably lowest known.

One more interesting feature is aluminum back panels, protecting EMI-sensitive components from interference of the power transformers, AC-line and other sources. This back panels also have holes for the Eurorack bus wire. Nice feature would be holes for trimpots adjustment.

Any module can be purchased on the web-site, assembled or as DIY options kit: board with installed or not installed SMD-components, panels, TempCo. The 15v versions or versions with modified characteristics are available. The prices are attracting for top-class equipment. Unfortunately, full kits are not available, but there are all necessary documents and links on the product pages such as part lists, Mouser projects, Small Bear Shopping Carts, etc.

Note: I have omitted common descriptions of the modules to reduce translation time. You can find detailed descriptions in English on the corresponding product pages.

L-1 Quad VCA/Mixer

l-1_quad_vca_mixerThis 14HP module is a hybrid of quad VCA and 4-channel VC-mixer. It is based on THAT2180 VCA IC. It is probably the best available VCA chips nowadays. Just see the datasheets or read the board discussions. Also Laman uses Analog Devices OPA2604 for audio. That kind of design have advantages over traditional designs based on OTA-chips, CA3080, LM13700 or SSM/Curtis. It gives very clean amplification useful for musicians that record multi-layered material. The summary impression is highly positive, unless I miss knobs defining initial amplification level as on the Doepfer A-131-style modules. Nevertheless, I think that this VCA is meant to be used with ADSRs.

L-1 Tube VCA

l-1_tube_vcaThis module has long developing history coming from Ken Stone’s CGS65 Tube VCA modified by Muff Wiggler user PrimateSynthesis. Alex Laman added a feedback section and brought a schematic to his high standards. The result is very interesting.

Module is based on soviet penthode 1Ж24Б (1Z24B). This design proposed by Ken Stone is simplier that any traditional discrete VCA based on transistor current mirror, though this design can’t give precision comparable to solid-state designs. There is another important thing. The saturated vacuum tube limits the signal smoothly, like a compressor. Further gain ends up in the effect of wave folding as it was called by Ken Stone. The phase of the wave is inverting if amplitude exceeds some critical point and that adds pleasant even harmonics to the signal being processed. This is the primary feature of the tube Overdrive.

But Tube VCA differs from ordinary stomp-box. It have voltage input that controls saturation of the tube. Also it can provide a feedback that gives another flavour of distortion. 10HP-wide module has two signal inputs, 1 CV input and 1 output. The second input substitutes internal feedback channel when a jack is inserted. The amount of the feedback is not CV-controllable, but control can be achieved with another VCA. There are special holes on the front panel giving access to the two trimpots changing relative gain. (technically — DC offset of the signal coming to tube) There is also a switch that selects between two “presets” adjusted by these two trimpots. The switch positions are named Dist and Clean.

tube_vca_wave

The good reason to use this module is the ability to waveshape harmonically-poor signals such as sine wave. You can take the best from Tube VCA overdriving the Sine wave and making it complex. It’s much less practical to use it with rich waves such as Sawtooth.

If you’re going to get the DIY kit, please pay attention to the note about power socket given on the product page. Alex Laman made overlay drawings for Cwejman cables that are not compatible with traditional Eurorack cables like Doepfer. Wrong orientation may cause short-circuit and damage to the protection diodes or resistors/beads.

tube_vca_power

2180VCF

l-1_2180vcfI’ve noticed that each engineer has his own beloved techniques: someone likes OTA’s, someone likes CMOS, MCUs or transistors. No doubt that Alexey Laman likes the THAT2180 chip. The 2180VCF is the filter based on that chip. In fact, the schematic of this 2-pole multimode filter is inspired by OTA-design but it is modified for VCA chip. This filter is very low-noise and functionally precise. As Laman says, the self-oscillating 2180VCF can sound in tune over 5 octaves that making it usable as low-THD sine-wave VCO. With Tube VCA even more shapes are possible.

As the case of VCA/Mixer, this VCF sounds very clean with almost no thermal noise at all. All used chips and capacitors are high-quality components like used in Quad VCA.

Module also has some disadvantages. Alex admit that some of these filters may not self-oscillate and propose a simple modification (resistor replacement). I’ve got one of these modules that also can self-oscillate only in Bass-boost mode. Also there is no control over input volume while there is free knob-size blank space on the panel.

Let’s talk more about self-oscillation. It leaves weird feeeling. The level of the feedback is limited by 1N34A germanium diode. This never allows oscillations to be louder then input signal. This is interesting idea, but limiting is done simply by some kind of diode clipping that causing unwanted high harmonics in the feedback oscillations making them rich and obsessive. At least in LP mode I find high frequency content above cut-off frequency completely incorrect. However this could be counted as distinctive sound of the filter. The similar effect is present on the Doepfer A-106 Xtreme Filter. You can bypass clipping simply by removing the diode, so consider this an option.

Module tests

I made some tests using RME FireFace800 audio-interface and Steinberg WaveLab 5 (16/44).


Various modes od the 2180VCF. The filtered wave is coming from the Doepfer A-111 High-End VCO.
Listen to: sound.
Watch for: nothing.


Sine-wave of self-oscillated 2180VCF. The resonance level is minimal required for self-oscillation.
Listen to: sound
Watch for: amplitude and shape of the waveform.


The same sine processed by Tube VCA. All knobs are turned by hand.
Listen to: saturation.
Watch for: waveform morphing.


The same sine wave went through patch consisting of Tube VCA, Quad VCA/Mixer and 4ms PEG. PEG is used as quadrature generator that controls Tube VCA and a channel of Quad VCA, which is inserted into feedback loop of the Tube VCA.
Listen: effect.
Watch for: waveform morphing.


Comparison of dynamic properties and noise of 4 different VCA. The sawtooth of the Doepfer A-111 (CEM3340) goes through an LP-channel of the 2180VCF. Cutoff frequency is constantly sweeping with 4ms PEG. The output goes to different VCA controlled by cycled ADSR-generator. Every example plays twice in the following order: L-1 Quad VCA/Mixer, L-1 Tube VCA, Doepfer A-132, Doepfer A-131 (The both Doepfers are old, with CA-3080).
Listen to: noise, dynamic smoothness, saturation.
Watch for: the same.


Demo of the 2180VCF self-oscillation staying in tune. Sequencer controls pitch of the A-111 and cut-off frequency of the 2180VCF. Pure wave comes first, then comes same wave with emphasized harmonic.
Listen to: tune
Watch for: nothing.


Comparison of 5 different filters. (Recorded through modified Doepfer A-138 mixer with TL061 replaced by military AD OP470) Short pulses are going through filters that set up identically to achieve clear and distinct resonance, but not to self-oscillate. Every example is 32 click long with sweeping cut-off frequency. The frequencies are very close in each example. All filters except of L-1 are Doepfer. The filters are coming in the following order: 1. 2180VCF (THAT2180). 2. 2180VCF (+ Bass Boost). 3. A-106-6, 2LP output (CEM3379, input OpAmp is replaced by OP470). 4. A-121 (CEM3320). 5. A-120 (Transistor Ladder). 6. Dark Energy filter (CEM3394). All clips are normalized to -3dB peak!

Listen to: noise, timbre, pureness of the oscillation, basses.
Watch for: Low frequencies

DIY

A I said before, L-1 DIY-kits are only partial and all through-hole components and hardware must be provided by customer. Common components may be purchased at Mouser, cables and jacks at Erthenvar, pots and knobs at Small Bear. Delivery rates varies.

Conclusion

L-1 modules are very good in general. All reviewed modules are useful and high-quality. Low-noise design is very valuable. Graphical design is gentle but functional in the opposite to Make Noise and WMD production. Alex is planning to expand his model range soon. For example, he’s going to make a VC-ADSR and a VCO. L-1 has great potential and I hope that further production will be perfect. Good luck,  Alex!

The Modularsynth.ru Rating

Tube VCA: 8/10
Quad VCA/Mixer: 10/10
2180 VCF: 8/10

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