The SPL TwinTube Dual-Channel Processor provides perhaps the two single most important and beneficial artifacts generated by tubes: Saturation and Harmonics. The warmth, presence and suppleness analog tube and coil filtering provide can enrich any production, almost regardless of the music genre.
The TwinTube's saturation effects are sonically comparable to the effects of tape saturation which adds warmth and loudness and emits subtle-to-clear effects while harmonics create more presence and clarity without adding appreciable sound levels, as is the case with EQs. Harmonics help to move signals to the front of a mix and can add a further richness to the sonic source.
These effectual changes of the sound character by the TwinTube can work for all kinds of signals, such as vocals, acoustic guitars, drums, strings, brass, etc.
Saturation effects are generated through the tube being pushed to and beyond its normal operating limits. In contrast to semiconductors, which at that point would cause a harsh sound, a tube thus pushed to such levels does not clip from reasonable over-level. Once approached, this pushed level limits and thereby produces its typical tonal result, which in audio signal processing can have such often profitable aural effects. On one hand (and depending on the amount applied), from subtle to extensive harmonic distortion and on the other hand, a compaction of the sonic event, that is, a limiting effect that exhibits a pleasant, rounded or soft sound. Acoustically, and also in its range of applications, this can be compared very well with tape saturation effects.
Harmonic distortion and limiting are the generally known "classic" tube effects, which are today cornerstones of much sound processing. But other less known and potentially important effects are a tube's ability for improving presence and spatial qualities through its processing of specific regions of the overtone series.
Here we refer to only two significant examples, of course without suggesting completeness. The effects and results described here can be applied to many other instruments:
Optimizing vocal tracks is a highlight among the processing applications of the TwinTube. Often further EQing is not necessary anymore in order to lift a voice from a mix and get it up front. A recommendation for female voices: HARMONICS switch to 6, HARMONICS control to about 2 o'clock, SATURATION to about 12 o'clock.
With these settings the described effect should be clearly audible and from here individual tracks can be optimized. With female voices we suggest trying HARMONICS switch settings 6 and 10 while switching between 2, 3, and 6 with male voices.
2. Acoustic Guitars
The success in treating electric guitars depends on previous recording and processing gear and techniques: if tube amps and further effects were already applied, it is hard to foresee how much the TwinTube can contribute when optimizing or designing a sound.
In contrast to electric guitars, there is a huge potential in processing acoustical guitar tracks. Guitar-picking sounds can be intensified, and in general, tube saturation and limiting can improve loudness and condense the sound. Presence is emphasized and the instrument cuts through a mix much better without raising levels too much. A well-chosen amount of harmonic distortion always adds some roughness which may often add a nice touch to several playing styles.