Andy, your Vertigo VSC compressor has already become a modern classic. What has been driven you to create such a device?
I really like VCA compressors. VCA technology gives you a lot of freedom in design and development and the user gets a very flexible tool at the end. I was very unhappy with all VCA compressors on the market around 2000. Those were not very flexible for different applications. These units were working good in one certain setting only. Changing threshold or other parameters was fiddley and so on. But the main point starting the VSC project was the new IC VCA based compressors sounded one dimensional and boxy.
Does this mean your design goal was to have a more transparent sounding device or does the VSC also adds a certain sound but just in a different/better way?
Transparency without sounding clean and artificial. The discrete Vertigo VCAs deliver up to 0,6% THD. Distortion can deliver depth without sounding muddy.
Does this design favour certain harmonics or – the other way around – supresses some unwanted distortions?
The VSC adds a different distortion spectrum depending when increasing input level or adding make-up. The most interesting fact is that most of the distortion and artifacts are created in the release phase of the compressor. The distortion is not created on signal peaks. It’s becoming obvious when the compressor sets back from gainreduction to zero gainreduction. Similar to a reverb swoosh… after the peak that was leveled.
Where does your inspiration comes from for such technical designs?
With my former company I repaired and did measurements on many common classic and sometimes ultra-rare compressors. Some sounded pretty good but were unreliable – some were very intuitive in a studio situation, some not…
At this time I slowly developed an idea what kind of compressor I would like to use in daily use.
From your point of view: To which extend did the compressor design principles changed over the years?
The designs changed a lot. Less discrete parts, less opto compressors (because a lot of essential parts are no longer produced), tube compressors suffer from poor new tube manufacturing and some designers nowadays go more for RMS detection and feed forward topology. With modern components there was no need for a feedback SC arrangement anymore. I think RMS is very common now because of its easy use at the first glance. For most applications I prefer Peak detection.
Having also a VSC software version available: Was it difficult to transfer all that analog experience into the digital domain? What was the challenge?
In my opinion the challenge is to sort out where to focus on. What influence has the input transformer or the output stage? Yes some of course. Indeed most of the work was going into emulating the detection circuit.
Which advantages did you experienced with the digital implementation or do you consider analog to be superior in general?
I am more an analog guy. So I still prefer the hardware. What I like about the digital emulations is that some functions are easy to implement in digital and would cost a fortune in production of the analog unit.
Any plans for the future you might want to share?
At the moment I struggle with component delays. 2021/22 is not the right time for new analog developments. I guess some new digital products come first.
Related Links
Variety Of Sound 
[…] This year I already had the chance to talk to Vladislav Goncharov from Tokyo Dawn Labs and Andreas Eschenwecker from Vertigo Sound which gave some detailed insights about creating analog and digital audio devices, especially […]