MATRIXSYNTH: gstormelecto XaVCF Oberheim OB-Xa Eurorack Filter Module

Sunday, February 16, 2020

gstormelecto XaVCF Oberheim OB-Xa Eurorack Filter Module

gstormelecto XaVCF Test Filter Circuit [Audio Only Demo]

Published on Feb 16, 2020 gstormelectro

"Audio and Video by G-Storm Electro c. 2020

I've been getting requests for demos of my upcoming XaVCF module.
It will be a eurorack adaptation of the OB-Xa filter.
More info at
You know this sound from Rush Tom Sawyer and Van Halen's album 1984.
While we're all eagerly awaiting the module prototype I thought
I would share a brief sampling from a mini-lab test circuit.
A more thorough overview of the module will happen when it gets built.
So be on the lookout for that one in the near future.

The XaVCF will sound pretty far out.
We're talking about full on intergalactic blast off here.
Headphones recommended. BUT!...
Watch your levels, thick resonant sweeps ahead!
Prepare for ignition...

0:00 Classic 2-Pole resonant drop sweep
0:16 4-Pole Resonant Riser
0:41 2-Pole pure self-oscillation sweep w/ tracking
0:56 ...add both VCOs back in, slow sweep through sweet spots
1:40 2-Pole pure self-oscillation musical sequence
2:05 1-Pole Bandpass LFO modulated

VCOs: 101-VCF, Pittsburgh Synthesizer Box
LFO: Batumi
Delay: Timefactor
Sequencing/Control: Beatstep Pro
No mastering, no eq, nor additional post-effects added."

"The XaVCF is a faithful adaptation of the OB-Xa filter in Eurorack with added features.

As with the original, the XaVCF has two filter circuits to choose from! The heart of both designs having each its own Alfa reissue AS3320 chip. The XaVCF has the original Modes: a 4-Pole standard Lowpass circuit, and a 2-Pole Lowpass derived from a State-Variable circuit. Additionally there are 1-Pole Bandpass and Lowpass modes not available on the original!

Both filter circuits on the XaVCF not only have musical self-oscillating resonance w/ CV control, but the frequency cutoff can be tracked V/Oct using the CV2 input jack. In this way the XaVCF can be used as a sine wave oscillator. Unlike some older classic filter designs, the XaVCF retains a lot of low end at higher resonance.

The XaVCF is drenched in that fat and creamy wall of sound you’ll not soon forget. Are you ready for the Xa experience?

* Two selectable filter circuit configuration Types: Type I-SVF 2-Pole Lowpass, and Type II 4-Pole Lowpass.
* Additional Modes: Type I 1-Pole Bandpass, Type II 1-Pole Lowpass
* Two voltage controlled input jacks for Frequency CUTOFF w/ signal attenuators. CV1 is an extended range input capable of providing some boost to weaker control signals. The CV2 input will track V/Oct when its pot is fully CW.
* A voltage controlled input jack for RESONANCE w/ a signal attenuator CV3.
* Two audio signal input jacks w/ individual attenuators. Above midpoint, these inputs can overdrive the filter from most Eurorack oscillators and audio sources. This is especially useful in Bandpass Mode to compensate its weaker audio output signal.

Available late February 2020
Be sure to check out my other cool modules in my Reverb Store"

No comments:

Post a Comment


©2019 Matrixsynth - All posts are presented here for informative, historical and educative purposes as applicable within fair use.
MATRIXSYNTH is supported by affiliate links that use cookies to track clickthroughs and sales. See the privacy policy for details.