Harmonics Generator for 2nd and 3rd Harmonics Distortion
The Harmonics Generator combines several sections to produce and add 2nd and 3rd harmonics. The possible effects cover the range from brightening up the mix in a way that cannot be achieved using equalizers, to the simulation of the distortion of vintage gear and the colorisation, wrinkling, and/or soiling audio signals in specific frequency bands. The module is a useful tool for special treatment, not only with mastering.
The generator allows adding general 2nd and 3rd harmonics and has two generator sections that are combined with bandpass filters to limit the frequency range of added distortion. The generated harmonics can be added in phase or phase reversed.
This set covers the entire range of conceivable applications. The control ranges are sufficient to accomplish everything between a small colorisation and total distortion. The harmonics generator allows unobstrusive application of the different effects instead of specious and pushing effects. In particular, the addition of third harmonics offers very interesting colorisation effects if used appropriately, since the quint above the octave adds colors that cannot be achieved by 2nd harmonics alone.
Due to many decades of listening to recorded music, we all got used to the typical side effects of audio recording. Distortion, mainly 2nd and 3rd harmonics a directly connected not only to amplification but to the analog storage methods on disc and tape. The absence of distortion is usually not considered as advantage. Distortion free recordings are described as 'clinical' or 'cold', while an appropriate, small amount of distortion is often considered as 'warm' and 'musical'; however, if the distortion is too high, it is always getting disturbing.
During the analog ages, with analog tape recorders, there was no problem with 'warm' and 'musical' souding mixes; however, there were many other annoying things and problems. Digital audio however, which is free from those effects but has many other bothering problems as well, can benefit from some artificial 'warm' and 'musical' distortion; not all the time, but it's always worth to give it a try. In many cases a mix will sound subjectively better with a little distortion.
In addition, the balance between 2nd and 3rd harmonics is important for the subjetive impression. Two much of one or the other, again results in this 'I'm missing something' feeling.
The Harmonics Generator U794 has three sections:
The two controls in this section determine the total distortion of the device. The k2 control just adds pure 2nd harmonics that are not frequency depending. The distortion is proportional to the level but not in a linear relation. An appropriately increasing amount of distortion is added over a range of approximately 20 dB. The control law of the k2 pot allows adding small values as well as total distortion at high levels when all to the right. 2nd harmonics are produced by transistors, tubes, and any other kind of active components that can be used for amplifcation. This kind of distortion adds octaves; so it won't sound like distortion as long as the percentage is not too high, since octaves are part of the spectrum of any sound.
The k3 control does two things at a time. A special network that alters the input/output characteristics of the device and produces mainly 3rd harmonics is changed in the influence on the audio signal, depending on the position of the control. If the control is all to the right, a signal is distorted already at an input level of 0 dB. Any higher level causes more distortion, even though the characteristic is designed to increase distortion slowly. When all to the left, no distortion is added. The network simulates the behavior of a pentode but the transisition range from the begin of distortion to teh clipping point is a lot larger, which allows adding distortion more precisely. In addition, the input transformers are affected in a way, that higher levels produce the typical distortion of a bad quality tranformer. This kind of distortion occurs only in the low frequency range, and is caused by the magnetic saturation of the transformer's core. Both effects are combined in a way, that the relation between network and transformer distortion matches the distortion components of a vintage pentode amplifier with transformer. The distortion that is added with the k3 control increases with the level and is higher at low frequencies.