The 5001 Analog Synthesizer models a dynamically patchable, semi-modular, monophonic analog synthesizer from the late ’70s. The audio engine and user interface are based on the ARP 2600. The front panel and extension panel on the keyboard present a majority of the controls and I/O from the original synth. The layout has been slightly modified for conciseness and to support stereo audio input. The drawbar in between the keyboard and the front panel can be dragged up or down to maximize either view for ease of use.
Getting Started with Normalled Connections
If you’ve never worked with a synth like this before, or if you need a refresher, each control input is internally connected to an output as labeled on the synth without having to make any additional patches. Historically, this conserved patch cables for relatively frequent connections, allowing for more experimentation if cables were limited as well as kept the visual layout of a patch much simpler by avoiding unnecessary clutter. In a software incarnation with virtually unlimited patching normalling also serves as an effective starting point for learning the instrument. If you’re not sure how to begin or if you want to get to a usable sound fairly quickly, start by creating a new preset with no default patches, turn up some sliders, and start playing. Note that we’re using the term patch to refer to an individual connection between inputs and outputs as well as a generic term for the whole preset once all patches have been made, e.g. a patch can refer to either a single connection or the preset itself made up of multiple connections.
Key sliders to getting initial sounds include:
- Section 8: Mixer Slider No. 2 (VCA)
- Start here, enable output to speakers
- Section 7: VCA Sliders No. 1 (VCF), and No. 3 (AR)
- Next, enable output from VCF
- Control volume with AR triggered by keyboard input
- Section 6: VCF Sliders Nos. 1-3 (VCOs)
- Route VCO square/saw outputs through VCF
- Increase Initial Filter Freq. for brighter sounds
During step #3 you should begin to hear sound when playing the keyboard as you increase the VCO input levels to the VCF. Note that the keyboard input alters oscillator pitch, adjusts filter frequency, and triggers the volume envelope all at the same time! This simple patch produces a filtered combination of the three VCOs, tuned to the same pitch by default, without involving any patching. The sound is gated by playing the keyboard via the VCA and AR envelope generator. From here you can begin to alter tuning, modify filter cutoff for different timbres, and adjust envelope attack and decay for dynamics.
Section Details
1 Stereo Preamplifier
Use the audio input selector in the app toolbar to choose Left and Right input channels: tap to assign L, double tap to assign R. Left and Right assignments can be the same channel for mono routing flexibility. With mono input buses, L/R automatically share the same channel.
2 Envelope Follower/Ring Modulator
The envelope follower generates a control voltage based on the amplitude of the supplied input signal. Note that the input is normalled to the sum of the Left and Right input channels (which is the same channel for mono input buses).
The ring modulator is a four quadrant multiplier producing the multiplication of two supplied inputs. Note that polarity is preserved such that phase can be inverted when supplying a negative input signal. The DC/AC switch inserts or removes DC blocking capacitors at each of the inputs. Select DC when multiplying control voltages, AC for strictly audio inputs.
3 Keyboard CV/Multiples
The keyboard control voltage (CV) is normalled to the VCOs and VCF, and is provided as an output here for additional routing.
The four multiples dynamically reconfigure based on their connections and can provide 1 input to 3 outputs, 2 summed inputs to 2 outputs, or 3 summed inputs to 1 output. Both voltage control and audio inputs are supported.
4 VCOs
The voltage-controlled oscillators (VCOs) have a range of 0.1 Hz – ~20 kHz, and 0.01 Hz – 30 Hz in low frequency (LF) mode. Frequency control has a range of +/- 2 octaves, fine tuning control has a range of +/- 1 semitone.
5 VCF
The voltage-controlled filter (VCF) has a range of 20 Hz – 20 kHz. Fine tuning control has a range of +/- 1 octave. Increasing resonance can cause self-oscillation near maximum.
6 Envelope Generators
There are two envelope generators producing either attack, decay, sustain, and release (ADSR) or attack, decay (AR) envelopes. They are normalled to the keyboard gate/trigger and have a manual control that can be tapped to trigger the envelope cycle. Additionally, an external source can be selected for gate/trigger which disables keyboard input. The keyboard gate/trigger are also made available here for external routing.
7 VCA
The voltage-controlled amplifier (VCA) supports two audio inputs and two control inputs. The initial gain can be used to “open” the VCA and set a default volume, applying additional control signals is additive.
8 Mixer/Reverb
The mixer section has several components related to system output. The Mixer sums two inputs to mono and provides a Mixer Pan control for the mono output. In addition to the mono output, the summed signal is routed to an internal Spring Reverb with separate Left and Right volume controls. Both the Mixer and Reverb outputs are made available for additional routing purposes.
In addition to the Mixer and Reverb outputs, a stereo Aux Input is provided as well as the full stereo System Output.
9 Internal Speakers
The Left and Right channels are routed through internal speaker emulations. Each channel can be separately blended between Direct and Speaker emulation outputs.
10 Noise Generator
The noise generator has two controls for spectrum (white, pink, etc.) and level, with one output. Increasing the spectrum control produces more high frequency energy by increasing the cutoff of the internal low pass filter.
11 Voltage Processors
There are four voltage processors. From the top, 1 and 2 are summed. The summed output and 3 have additional inverted outputs. And 4 is a lag processor, adding ramp and decay time to supplied control signal inputs. 1 and 3 are normalled to +10V which equates to the highest possible control voltage. 2 is normalled to Keyboard CV. And 4 is normalled to the Envelope Follower output.
Note that this section can be used to provide extra multiples if needed, as well as Keyboard CV inversion for interesting effects.
12 Sample & Hold/Switch
The Sample & Hold is driven by a clock signal provided internally or overridden by the External Clock input. The input, which is normalled to the Noise Generator output, is sampled based on the frequency of the clock signal and the sampled voltage is produced at the output. If supplied internally, clock speed is controlled by the second slider. Output level is controlled by the first slider.
The Switch is a bidirectional switch that reconfigures based on applied connections. The configuration can be either switching between A/B inputs to C [A | B >> C], or switching between A/B outputs from C [C >> A | B]. Switching is based on the same clock signal supplied to the Sample & Hold which can be overridden by the External Clock input.
13 Drawbar
The drawbar is provided for additional flexibility and can be used to resize the ratio between the front panel and the keyboard. This allows for more focus on patching or playing with smaller screen sizes.
The Keyboard
- Highest-note priority
- Note memory
- Tuning options
The keyboard is automatically routed to the VCOs and VCF via KBD ON switches, as well as provided in Section 3 with KBD CV output, with the Gate and Trigger provided in Section 6. The keyboard produces a monophonic output with high note priority and note memory, i.e. highest note wins, after releasing the highest note, control voltage remains present at the output.
14 Keyboard Controls
Keyboard controls include toggling between Variable (0.5x-2.0x) and Fixed (~0.8x-~1.2x) interval tuning, as well as selectable Tuning (+/-12 semitones) and Portamento (0s-0.5s) controls.
Note that the Tone Interval controls (Variable, Fixed) adjust pitch spacing relative to Middle C (C4). Increasing these values spreads notes further apart, decreasing brings notes closer together, enabling crude microtonal tunings.
Audio Unit Operation
- Section 3: DAW Clock Out
In addition to the specified controls above, a new output is made available when running SynthStamp as an audio unit. The DAW Clock output is provided in Section 3 which continuously tracks DAW BPM rates and re-syncs with measure playback so that rhythmic effects can be achieved in synchronization with DAW recording and playback.
