Tuesday, 6 October 2009

Silent Way CV Input - Digital Ghost Tracks

Ever wanted to record CVs to your DAW? Expert Sleeper's latest 'Silent Way' plug-in makes this possible.

'CV Input' brings Buchla and Subotnick's Ghost Tracks method into the digital age. The plug-in can handle bipolar CVs (LFOs etc.) and the 'recovered' CV can be output live or recorded for rearrangement or further processing.

To get the most out of 'CV Input' you'll need a DC-coupled Ring Modulator although for unipolar CVs (envelopes etc.) a standard linear VCA will do.

In beta testing, I tried a Doepfer A-133 VC Polarizer, Cwejman VCA-2P and the DC-coupled ring modulator in my VCO-2RM. The latter gave me the best, most accurate results. The A-133 is a good, cheap option but the lack of centre-indent on the manual offset pot made it tricky to zero the output precisely and meant the returned CV was asymmetrical. The VCA-2P was not as accurate because its 'linear' mode is in fact semi-logarithmic. Os at Expert Sleepers suggested that a calibration function to address these issues might be a possible future update.

So, does it work? The short answer is a resounding yes!

The caveat is that you might need to spend a few minutes setting up the plug-in for your system, but this is swift and painless. For example, you want to find the 'hottest' carrier level your audio interface can handle and balance that against the strength of the modulating CV to avoid clipping your VCA or RM. Then you will need to use the 'scale' knob to get a 1:1 match between 'original' and 'recovered' CV. Bear in mind that you might need a negative scale to counteract any anomalies in your system.

Here's a short clip featuring three tracks of one VCO following the same bipolar random CV. For each successive 'harmony' track I adjusted the decoder's scale.

Nice one Os - now all we need is a pitch to CV converter!

For more Silent Way tips and tricks read this post.

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