the beauty of opto-electrical compression – volume 2

When I was looking for a sophisticated stereo compressor for the outboard studio rack a year ago, I was surprised to see how many of the more interesting models now use opto-electric compression technology. Whether transparent or coloring, tube or solid-state amplifiers, transformer or transformerless, even two-channel layouts in mid/side encoding: far advanced compared to all the classic mono replicas.

Optical compressors are usually characterized by their distinct program-dependent compression behavior, mainly based on a physical memory effect in the detector itself. Other subtle nuances are found across the frequency spectrum that affect timing and curve characteristics, creating a complexity that cannot be reduced to simple two-stage controlled release curves, and which is the beauty of opto-electrical compression in its entirety.

Significant audio signal colorations, however, are shaped not by the gain reduction circuitry but by the make-up gain amplifier, whether it is tube or solid-state. Here, the audio transformer also plays an important role in polishing the transients and creating a cohesive sound.

ThrillseekerLA was designed from the beginning in 2012 as a modern stereo compressor with exciting sound coloring possibilities. It is a compressor with authentic opto-electric control behavior in feed-forward circuit topology.

The upcoming mkII update is a technical redesign dedicated solely to improving the sound. It delivers a unique box tone with thrilling bass and elegant top end void of any harshness in the mids. The compression not only glues everything together effortlessly, but also enhances the stereo image by adding depth and dimension.

The release is scheduled for mid-December.

The TesslaSE Remake

There were so many requests to revive the old and rusty TesslaSE which I’ve once moved already into the legacy folder. In this article I’m going to talk a little bit about the history of the plugin and its upcoming remake.

The original TesslaSE audio plugin was one of my first DSP designs aiming at a convincing analog signal path emulation and it was created already 15 years ago! In its release info it stated to “model pleasant sounding ‘electric effects’ coming from transformer coupled tube circuits in a digital controlled fashion” which basically refers to adding harmonic content and some subtle saturation as well as spatial effects to the incoming audio. In contrast to static waveshaping approaches quite common to that time, those effects were already inherently frequency dependent and managed within a mid/side matrix underneath.

(Later on, this approach emerged into a true stateful saturation framework capable of modeling not only memoryless circuits and the TesslaPro version took advantage of audio transient management as well.)

This design was also utilized to supress unwanted aliasing artifacts since flawless oversampling was still computational expensive to that time. And offering zero latency on top, TesslaSE always had a clear focus on being applied over the entire mixing stage, providing all those analog signal path subtleties here and there. All later revisions also sticked to the very same concept.

With the 2021 remake, TesslaSE mkII won’t change that as well but just polishing whats already there. The internal gainstaging has been reworked so that everything appears gain compensated to the outside and is dead-easy to operate within a slick, modernized user interface. Also the transformer/tube cicuit modeling got some updates now to appear more detailed and vibrant, while all non-linear algorithms got oversampled for additional aliasing supression.

On my very own, I really enjoy the elegant sound of the update now!

TesslaSE mkII will be released by end of November for PC/VST under a freeware license.

ThrillseekerXTC mkII released

ThrillseekerXTC – bringing mojo back

ThrillseekerXTC mkII is a psychoacoustic audio exciter based on a parallel dynamic equalizer circuit. It takes our hearing sensitivity into account especially regarding the perception of audio transients, tonality and loudness.

The mkII version now introduces:
• Plugin operating level calibration for better gainstaging and output volume compensated processing.
• A reworked DRIVE/MOJO stage featuring full bandwidth signal saturation and a strong
focus on perceived depth and dimension. It provides all those subtle qualities we typically associate with the high-end analog outboard gear.
• Special attention has been taken to the mid frequency range by introducing signal compression which improves mid-range coherence and presence.
• Relevant parts of the plugin are running at higher internal sampling frequencies to minimize aliasing artifacts.

Available for Windows VST in 32 and 64bit as freeware. Download your copy here.

FerricTDS mkII released

FerricTDS mkII – the updated award winning Tape Dynamics Simulator

New in version 2:

• Introducing operating level calibration for better gainstaging and output volume compensated processing
• Metering ballistics revised and aligned accordingly
• Updated tape compression algorithms increasing punch, adding 2nd order harmonic processing, less IMD
• Updated limiter algorithm featuring ADC style converter clipping
• All non-linearities are running at higher sampling frequencies internally
• Adding a sophisticated analog signal path emulation

Available for Windows VST in 32 and 64bit as freeware. Download your copy here.

The Korg SDD-3000 – perfect for LoFi?

By accident, I recently stumbled upon the UAD Korg SDD-3000 digital delay version. When I noticed that they modelled also its amplifiers as well as the 13bit converters they immediately got my attention. Having also high- and low-pass filters on board, this could easily double as a great lofi device – so lets have a closer look.

As in the original hardware, the device offers several gain stage adjustments for both input and ouptut, intended to match different instrument or line level signals. These amplifiers are always in, no matter if the BYPASS switch is activated or not. Interestingly, UA also integrated this in its “Unison” interface feature as an preamp option.

Depending on how hard the input gain is driven, quite heavy distortion and saturation effects can occur. As soon as the Bypass is deactivated, the effect signal path containing the 13bit converted and HP/LP filtered signal can be dialed in with the LEVEL BALANCE. If this balance is now set to EFFECT only or just the WET SOLO option has been turned on (plus avoiding any amounts of feedback in this case) the device now offers a pretty much nicely degraded signal path for any sort of creative effects. Depending on the actual settings one can dial in now some really creamy or even gritty effects. Be aware, that this signal path contains an additional delay according to the DELAY TIME setting, of course.

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The analysis charts are showing – from left to right – the basic frequency response (in bypass mode), some example harmonic distortions when hitting the input gain quite hard and the filtered effect signal path frequency response according to the UI settings above. The slight frequency bump on the right side of the charts might be caused by the plugin oversampling filters – the original hardware does not show this and its spectrum ends somewhere around 17kHz.

As in the original hardware, all settings are just within limited ranges and so it is not that flexible in general. However, soundwise its pretty much awesome. Oh and by the way, it also doubles as a simple but impressive delay 😉

so, is analog signal path simulation still the trend?

NastyDLA – final teaser and release info

NastyDLA – technical architecture

simplified technical architecture

Internally, NastyDLA consists of quite a bunch of DSP processing building blocks which as a whole are summing up to an authentic signal path simulation of it’s analog models. The blocks and the according signal flow are shown in the diagram above. Basic signal flow goes from left to right except the feedback path which goes in the opposite direction.

With NastyDLA, signal path coloration already starts in the input stage which provides a complete model of both, frequency and phase response as well as dynamic saturation. It’s located in the dry path but all nonlinear processing and coloring can be disabled on demand so it remains as a simple input volume control then. But while switched in, the input stage can greatly contribute on getting the processed signal to fit right into a mix.