Expert Sleepers ES-8 USB Audio Interface User Manual
- June 3, 2024
- Expert Sleepers
Table of Contents
lorelei
User Manual
Revision 1.0
ES-8 USB Audio Interface
Copyright © 2021 Expert Sleepers Ltd. All rights reserved.
This manual, as well as the hardware described in it, is furnished under
license and may be used or copied only in accordance with the terms of such
license. The content of this manual is furnished for informational use only,
is subject to change without notice, and should not be construed as a
commitment by Expert Sleepers Ltd. Expert Sleepers Ltd assumes no
responsibility or liability for any errors or inaccuracies that may appear in
this document.
Introduction
Congratulations on your purchase of an Expert Sleeper “Lorelei”. Please read
this user manual before operating your new module.
Lorelei is a VCO (Voltage Controlled Oscillator) with quadrature sine outputs,
waveshaping, and sync/cross-modulation options.
The module has three waveform outputs, all affected by the same waveshaping
controls (a front panel knob and a CV input). The first offers a variable
pulse width square wave. The remaining two ofer waveforms are based on
quadrature (i.e. 90 degrees out of phase) sine waves. The waveshape control
progressively turns the first sine output into a triangle-like waveform; the
second sine output becomes a saw-like waveform.
The cross-modulation input is somewhat like the sync input found on more
conventional VCOs, but it has more nuances of operation allowing for a wider
choice of sounds.
The module is 100% analog, using discrete transistor OTAs.
House the module in a Eurorack case of your choosing. The power connector is a
16-pin Doepfer standard
. If using the power cable supplied with the module, the red edge of the cable
is closest to the bottom edge of the PCB and carries -12V. (“-12V” is marked
on the PCB itself next to this end of the connector.) Be sure to connect the
other end of the power cable correctly, again so -12V corresponds to the red
stripe on the cable.
1 http://www.doepfer.de/a100_man/a100t_e.htm
Power requirements
Lorelei draws up to 55mA on the +12V rail, and 54mA on the -12V rail.
It does not use the 5V rail.
Inputs and outputs
Lorelei’s input and output jack sockets are illuminated, lighting red for
positive voltage and blufor negative voltage. (Audio appears purple, since it
is a rapid alternation of positive and negative.)
Inputs with attenuators are indicated by a dotted line linking the socket to
its corresponding attenuator knob.
From top to bottom, Lorelei’s sockets are:
- Pitch CV input (1V/octave)
- Linear FM input
- Exponential FM input, with attenuator
- Cross-modulation/sync input
- Wave shape CV input, with attenuator
- Square/pulse output
- Sine/pseudo-triangle output
- Cosine/pseudo-saw output
Controls
In addition to the three attenuators, there is an eight-position octave
selection switch (white), a
Tune control (blue), and a Shape control (green).
The Tune knob will adjust the oscillator pitch by approximately one octave up
or down.
Wave shapes
The wave shapes CV input and knob together simultaneously control the
waveforms of Lorelei’s three outputs.
A curious result of the exact nature of the wave shaping applied is that at
the halfway point the perceived pitch of the sine and cosine outputs doubles.
Below are oscilloscope traces showing the three outputs as the Shape knob
moves from 0 to 10.
Waveforms are shown for Shapes of approximately:
| 0 | 2 |
|---|---|
| 3.5 | 5 |
| 6.5 | 8 |
10
Cross-modulation/sync
In a common-or-garden ramp-based analog VCO, oscillator sync works by
resetting the ramp integrator based on the frequency of the syncing signal.
Lorelei works quite differently, though similar effects can be obtained. In
Lorelei, the sync input essentially prevents the oscillator from oscillating
when the input is above a certain voltage (around 3.3V), but this is not an
on-off thing – the effect gradually applies as the voltage increases. The
upshot of this is that smooth waveforms (e.g. sine or triangle) for the
syncing input produce a different effect to, say, square or pulse waveforms.
Also, when using a pulse wave as the sync input, the pulse width of the signal
also affects the result quite drastically. In the examples below, Lorelei’s
output is at the top (in green) and the sync input waveform is at the bottom
(in magenta).
Sync from ±5V sine wave:
Sync from ±5V triangle wave:
Sync from ±5V ramp wave:
Ramp wave reduced in amplitude to just trigger the sync:
Sync from ±5V pulse wave with various pulse widths:
Calibration
There are two trim pots on the Lorelei PCB, as shown below:
“RV5”, marked “Amplitude”, sets the internal level of the module and so the
operating point of the wave shaping. It should be set so that the waveform
observed at the test point “TP2” is 2 Volts peak-to-peak. You should not need
to adjust this unless you find that the output waveforms cannot be set to
completely clean sine waves at either end of the wave shape knob.
“RV6”, marked “V/oct trim”, controls the pitch tracking of the oscillator.
This needs to be set carefully to obtain the best possible tracking. It is
factory calibrated, but you may find you need to recalibrate if your
environmental conditions are much different from those in the factory, or
simply as the module ages.
Where to get help
Email, forum, and social media links can be found at the bottom of every page
on our website 2.
Acknowledgments
Black and white photography by Israel Denadai 3.
2https://www.expert-sleepers.co.uk
3http://israeldenadai.com.br/bw