# Modular Diary

While taking a look at the difference between the Epoch Modular TwinPeak filter and the one that Rob Hordijk uses in his own system, I got curious about his Dual Fader module. At first I thought that it might not be all that relevant in the Audulus context, but the closer I looked, the more compelling I began to find it.

The NOVARS Research Centre has fortunately posted an extensive series of Hordijk tutorials (presented by the man himself) and I found it very useful to take a look at the two videos (#12 and #12a) in which he presents the Dual Fader.

My first take-away was the simple idea of using one half of a cross-fader as a VCA with an RMS curve, and so I put together a little Audulus VCA and a comparison patch with exponential and logarithmic curves.

# Modular Diary

I’ve also put together a version of the TwinPeak filter following the layout and design Rob Hordijk created for his own modular system. It doesn’t have the cross-fader that is a handy feature of the Epoch Modular version, but that’s not necessarily needed in the context of Hordijk’s system since it includes a Dual Fader module. There’s a directness and clarity in the pure symmetry of his design that I find very satisfying.

The hordijk-synths.info site appears to no longer be online, but can fortunately still be accessed via the Internet Archive’s Wayback Machine. I also discovered the recently established Hordijk Modular Blog, which has an enthusiastic entry on the TwinPeak filter that includes an informative video in which Hordijk himself explains how the design enables not only a bandpass filter, but one with two peaks.

# Modular Diary

Looking through, organizing, and reviewing the many Audulus patches that I’ve accumulated and worked on over the last year, I was reminded of the Hordijk TwinPeak filter. A simplifed version of it was included in the Blippoo Box that I’d put together, and I remembered that I’d meant to make a standalone version of it at the time – only to realize that that had already been tackled on the forum.

Here’s my fresh take on the Epoch Modular version demonstrated in the James Cigler video at the top of the forum thread, building on the updated modules and approaches that have been introduced over the course of the last year.