Studio Electronics Boomstar 4075 (ARP filter)

Monophonic analog synthesizer with flexible sound generation (2 VCOs, cross modulation, noise, ringmod) as well as overdrive and feedback. Loopable envelopes and a MIDI-syncable LFO are there for modulation duties. Patch sockets for contol voltages enable interfacing e.g. with a modular synth.

The synth is capable of many sounds, from mighty leadsm thick basses, crazy FM sounds to cutting sync sounds.
The version 4075 is equipped with a really good sounding ARP 2600 lowpass filter.

VCO1 has a six-position octave switch (from LO to 2´), sync, pulse width modulation and a sub-oscillator. Up to two wave forms can be mixed with the wave-mix switches: triangle/sawtooth or sine/pulse. VCO2 can be removed from the keybaord tracking, has six octave ranges, switchable wave forms (saw, triangle and pulse), a detune control and a control for modulation intensity with Env1 or Env2 as selectable modulation source. Cross modulation of VCO2 to pulse width or frequency of VCO1 is available, too.

The oscillators, the ring modulator and the noise are mixed in the mixer section at the bottom where you´ll find also the lovely feedback control and en external audio input.

The filter is a resonent ARP 2600 low pass filter with keyboard tracking (0%, 50% or 100%). Besides the modulation intensity control for Env1 there´s also a modulation control for VCO2 or the LFO as source.

The first ADSR type envelope is assigned to the filter. It can be inverted and even looped. The second ADSR also offers an inverting function, additionally triggering by the LFO and different keyboard trigger modes. In the DRONE position of the master switch the VCA stays opened what makes filtering external sounds possible without constantly pressing a key.

The LFO can be synched to the MIDI clock if desired, offers nine wave forms and can e assigned to the pulse widths or frequencies of the VCOs.

The VCA is being modulated by the 2nd envelope, has a volume control and two overdrive modes. in the lowest section left of the mixer you´ll find additional tiny controls for main tune, pitch bend intensity, glide time, dynamics and modulation intensity of Env1 to VCO1´s PWM.