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.

Getting the most out of the SPL Tube Vitalizer

In this article I’m going to share some analysis insights but also proposing an easy to follow 3-step approach for finding the sweet spot while processing any kind of material with this device.

Preparing for winter season: room heating with style

So, having now a Tube Vitalizer here on my desk (at least for some time), I was surprised about the lack of usable online reviews and background information. One just finds the usual YT quality stuff which might be entertaining in the best case but also spreads misinformation ever so often. To save those influencers honor it must be said that the Vitalizer concept is really not that easy to grasp and its quirky user experience makes it not easier. The manual itself is a mixed bag since it contains some useful hints and graphs on the one hand but lots of marketing blurb obscuring things on the other. Time to clean up the mess a little bit.

What it actually does

While easily slotted into the “audio exciter” bucket, some more words are needed to describe what it actually does. Technically speaking, the Vitalizer is basically a parallel dynamic equalizer with an actual EQ curve behaviour which aims to mimic equal loudness contours as specified in ISO226. Rather simplified, it can be seen as a high and low frequency shelving EQ to dial in a basic “smile” EQ curve but one which takes hearing related (psychoacoustic) loudness effects into account. It does this also by generating curves differently based on signal levels, hence the term “dynamic EQ”. And wait, it also adds harmonic content galore.

Taming the beast

To obtain an equal loudness contour the main equalizers center frequency must be properly set depending on the tonal balance of the actual source material. This center frequency can be dialed in somewhere between 1k and 20kHz by adjusting the Hi-Mid Freq knob which defines a cross-over point: while frequencies below that point gets attenuated, the higher frequencies gets boosted. However, this attenuation is already a signal level dependent effect. Opposed to that, the LF EQ itself (which actually is not a shelving but a bell type curve) has a fixed frequency tuned to 50Hz and just the desired boost amount needs to be dialed in. The LF curve characteristic can be further altered (Bass soft/tight) which basically thickens or thins out the below 100Hz area. Finally, this EQ path can be compressed now with the Bass Comp option.

A typical EQ curve created by the Vitalizer

On top of the main EQ path, the Tube Vitalizer offers an additional HF boost and compression option which both can be dialed in to complement the LF behaviour in a very similar fashion but in the high frequency department. Internally, both are in a parallel configuration and mixed back into a dry signal path. The according Process Level knob can be seen as a kind of dry/wet option but only for main the EQ part. The upper HF part is mixed back in separately by the Intensity dial.

Gain-Staging is key

For the EQ section as a whole, the Drive knob is the ticket for proper gain-staging. If compression can be dialed in properly for both compressors (as indicated by the blue flashing lights) input gain is in the right ballpark. One might expect to hear actual compression going on but it appears to be a rather gentle leveling effect.

Gain-staging for the output stage has to be concerned separately which might become an issue if the tube stage is activated and operates in shunt limiting mode. Now you have to take care about proper input levels since the Attenuators for both output channels are operating after the limiter and not beforehand.

Tube stage limiting: input (red) vs output (blue)

Which directly leads us to the additional harmonic content created by this device. First of all, there is always additional harmonic content created by this device, no matter what. One might expect the device to not show any such content with the solid state output stage but it actually does. The tube output stage just increases that content but signal level dependent of course and 2nd order harmonics are always part of that content. A serious additional amount of harmonics gets added as soon as the HF filter gets engaged by dialing in Intensity (and LC Filter mode activated!) but this sounds always very smooth and natural in the top end, surprisingly.

Delicious content

Also impressive is the low noisefloor for both output stage modes, tube and solid state. The first one introduces pretty strong channel crosstalk, though.

Workflow – Finding the sweet spot in 3 easy steps

Initial condition:

• Drive, Bass, Bass Comp and Intensity set to 0
• Device is properly gain-staged

1. Set Process to 5 and now find the best fit for Hi-Mid Freq for the given source material. For already mixed 2bus stuff you can narrow it down to 2-3kHz most likely.

2. Dial in Bass (either left or right depending on source and taste) and some compression accordingly.

3. Only then dial in some further HF content via Intensity and some compression accordingly. Adjust HF Freq so it basically fits the source/taste.

Workflow – Tweaking just one knob

My good old buddy Bootsy told me this trick which works surprisingly well.

Initial condition:

• Left most position: Bass
• Right most position: Bass Comp, High Comp, High Freq
• 12-o-clock position: Drive, Intensity
• Hi-Mid-Freq set to 2.5kHz

Now, just dial in some (few) Process Level to taste.

He also recommends to drive the input to some extend (VU hitting the red zone) using the Tube stage in limiter mode while always engaging LC Filter mode for HF.

Thrillseeker XTC – behind the scenes

The basic idea to build a VoS style Enhancer/Exciter was already there way earlier but to that time it simply wasn’t doable until my ‘stateful saturation’ approach emerged. Later on and when I asked “how a modern exciter/enhancer should look like“, several concepts were laid out on the drawing board and I knew that with this exciting (sic!) new approach they all would be accomplishable w/o any compromises. Finally, one of them made it into a prototype which led to ThrillseekerXTC.

Old or modern approach?

So, is the audio Enhancer/Exciter just an ancient relict from the days of dull tape recordings or still a valid concept today? In the digital age, technology and production techniques completely changed and of course the production aesthetics did also. Opposed to the old approaches of audio excitation which mostly were focusing on high frequency loss restoration, the demand shifted towards other tasks as well. Presence and definition in the (upper) mid range is the name of the game and getting the low-end right is the key in a modern production. Instrument separation in a busy mix is a tough challenge, also.

What the heck is Mojo?

In some other cases (mostly digital productions) – definition, presence and transparency is all there but at the cost of a rather thin or sterile sounding production. Even worse, the HF department might be exaggerated too much during the processing chain and taming and sweetening is a challenge then. Some of the artifacts that we’ve found in certain analog devices might add tonal qualities described as thick, fat and round by ‘pleasingly degrading’ a sound source. This is what Mojo is all about. Whether that’s some circuit crosstalk, tape flutter or transformer distortion stuff alike.

how a modern exciter/enhancer should look like

Well, that’s exactly what I would like to know from you! Is it just an ancient relict from the days of dull tape recordings or still a valid concept? Opposed to the old approaches of audio excitation: What should such a device offer for todays modern audio production? And what would separate it from the common tools like compressors, transient designers and equalizers? Is it needed for any specific production stage? Which one? What exactly needs to be “enhanced”? Does all the different distribution formats and listening environments play a role? Psycho Acoustics? Question upon question ….

ThrillseekerLA – released today

introducing ThrillseekerLA

ThrillseekerLA – digital stereo leveling amplifier with truly analog qualities.

At a glance

• Sophisticated and deep gain riding full of musical character and attitude but with virtually no inter-modulation (IM) distortion artifacts
• Feedback compression design w/o any samplerate based delay in the loop
• Classic input level driven two knob design with additional manual attack and release time interventions
• Highly program dependent envelope timing adoption offering attack times ranging from “instantaneously” up to around 100ms and release times from 30ms up to several seconds
• Mix level switch to adopt the plug-ins internal gain staging to mixing levels at around -18dBFS
• Custom SC filter option to attenuate the SC bass response while slightly boosting the HF spectrum
• Additional one pole (6dB per octave) SC low-cut filter adjustable from 20 to 500Hz
• External sidechain support
• Switchable Input/GR/Output metering display
• Variable compression range control from 0 to 100%

announcing the “Thrillseeker” audio plug-in series

I’m bringing sexy back

The brand new and upcoming Variety of Sound Thrillseeker audio plug-ins series is going to be a plug-in collection premiering Stateful Saturation which is a sophisticated DSP core system for musical harmonic distortion generation based on authentic and truly stateful non-linear models.

Stateful Saturation takes advantage of some sought after analog qualities and preserves them accurately during their transfer right into the digital domain:

• high frequency shimmer and sheen without digital harshness
• depth and ‘3d’ imaging side effects before distortion itself becomes apparent
• audio transient dynamics that remains vibrant and alive
• natural and impressive bass response

Stateful Saturation opens the door for quite a number of amazing applications ranging from smooth harmonic exciters up to convincing amplifier effects and the DSP core can easily be set in context whether it’s a compressor output stage or a preamplifier circuit, just to name the two.

the side effects of intermodulation in audio processors

typical IM distortion in a digital compressor

The general and most obvious effect of intermodulation components in audio signals is distortion of course – hence the concept of “intermodulation distortion” (aka “IM distortion” or simply “IMD”). IM distortion and harmonic distortion are two pairs of shoes and must be defined individually as already shown in the short essay about “myth and facts about aliasing” but more on this later on.

The existence of intermodulation components can affect the performance of an audio production in various ways. In the best case, IMD components are a desired artistic effect e. g. to obtain heavily crushed audio effect signals but in the worst and rather common case, they are one of the contributing factors which deteriorate the overall audio quality and might ruin a production.

towards stateful saturation – very first audio shots

Around a year ago or so I’ve already started to look into a couple of stateful non-linear models which could be more suitable for a musical and convincing digital saturation experience. To make it even more harder, they should avoid the usual drawbacks such as huge latency or insane cpu consumption – if ever possible of course.

Meanwhile, my journey into the non-linear DSP land has made an important stopover with a first prototype implementation for such an approach, yielding a DSP core for musical harmonic distortion generation based on a stateful model. This opens the door for quite a number of interesting applications such as harmonic exciters or devices which needs convincing amp models whether thats a compressor output stage or even part of a guitar amplifier effect.