Expert Sleepers intros all-analog Eurorack modules: Lorelei, Ivo & Beatrix

SYNTH ANATOMY uses affiliation & partner programs (big red buttons) to finance a part of the activity. If you use these, you support the website. Thanks! 

Expert Sleepers goes analog with three new fully analog transistor OTA-based modules, Lorelei a VCO, Ivo a filter, and Beatrix a versatile phaser.

Digital Eurorack modules have made rapid development in recent years. You can find deep digital oscillators, multimode filters but also powerful multi-functional modules with 50+ functions. Yes in a single, tiny module. One of the best known is Expert Sleepers, a developer from UK who has so far specialized in digital modules such as the Disting Mk4, ES-9 audio interface, and more.

Today Andrew shows three new modules that turn Expert Sleepers upside down. These are the company’s first compact, all-analog modules: Lorelei, Ivo & Beatrix

Expert Sleepers Lorelei

Lorelei VCO

Lorelei is an analog VCO with waveshaping, and sync/cross modulations using discrete transistor OTAs. The module has three distinct waveform outputs, all of which use the same waveshaper. The first offers a square wave with variable pulse width and modulation (PWM). The two others are based on quadrature (i.e. 90 degrees out of phase) sine waves.

With the waveshape, you can smoothly turn the waveforms into new ones. Thus, the first sine output becomes a triangle-like waveform, and the second sine a saw-like waveform. Especially those between, indefinable results can be very exciting here. Besides the CV controllable wave shaping with attenuation, the module also features linear & exponential FM with an attenuator and a cross-modulation/sync option with a more nuanced touch. So it gives you a wider range of sounds.

Of course, you also have a 1V/octave input. Lorelei has an interesting, somewhat different feature set for an analog oscillator and that makes it very tempting.


Ivo also has some nice extras compared to other filters. It’s a discrete transistor OTA-based resonant lowpass VCF (8HP) with switchable 2-pole (12dB/octave) and 3-pole (18dB/octave) responses. You have CV control over the cutoff and feedback. There are two Cutoff patch points, the first is a 1V/octave input and the second with an attenuator for modulation. Resonance is labeled feedback and also has CV control with an attenuator that’s nice.

The module has two audio inputs, however only one output, thus it’s not a stereo module. Thanks to the second input, you can input two signals into the filter at the same time. A mini mixer in the filter is always very helpful. Perfect for two waveforms from the Lorelei VCO. Lastly, Andrew, the developer promises self-oscillation in 2-pole mode. Ivo is an interesting filter with a nice sound character.

Beatrix Phaser

The third new module is called Beatrix and is an analog phaser also based on discrete transistor OTAs. Beatrix, too, is anything but weak. It’s a phaser that offers voltage control over notch frequencies, effect depth, and feedback (resonance) making it very versatile. It also offers an unusual ‘offset’ control allowing you to sweep the filter notches without sweeping the resonant frequency.

Then, the phase switch disables the sound and turns the module into a kind of resonant peak filter. With the sum switch, you can invert the filtered signal and create phasing effects. At high feedback settings, Beatrix can self-oscillate. However, the front panel is factory set to stop shortly before self-oscillation. Phasers are less common in Eurorack but beatrix shows that we maybe need more of them. Definitely an interesting module.

Expert Sleepers lorelei, ivo & beatrix will be available during Summer for an MSRP: UK £159 (inc VAT), US $185 (exclusive of sales tax), EU €185 (inclusive of VAT)

More information here: Expert Sleepers

Available at our partner for pre-order

Perfect Circuit

Eurorack News

Be the first to comment

Leave a Reply

Your email address will not be published.