Splonkulator TM
Distortion Processor

Owner's Manual

Background

ORDINARY DISTORTION or CLIPPING is the main result of each of the unit's distortion section on the audio signal. This means the waveform output from the distortion section initially rises rapidly in response to the guitar input, until it cannot go any higher, or almost so. See FIG. 1: this shows what happens graphically, showing Guitar at A first in a positive swing of the example waveform, progressing through time into a negative swing. An amplification (making bigger) of A is shown at B, continuing at b'. If the amplifier distorts (clips) and cannot exceed the line at c', it continues from B to C instead. But suppose the distortion characteristic is different for a negative swing, more gradual, a gentler and more rounded waveform occurs as is shown at D. All these distortions change the sound that is produced in accordance to their nature.

POLARITY in this sense means if the audio signals within the unit are going up when the guitar signal go up, or are turned upside down. FIG. 2 shows an example of a distorted waveform A continuing at A', and another distorted waveform B continuing at B'. Note that B is "inverted" in polarity to A. A and B also have slightly differnt distortion characteristics and levels. C and C' shows (approx.) the results of adding together (mixing) A and B. In the Splonkulator both A and B would be created from a single guitar signal. Therefore the signal at C results from a difference in distortion characteristics and settings. This signal can be amplified back up to the desired level. The various signals cancel, oppose, or "fight" one another and sounds like it, due to the more jagged waveform.

Waveform addition can also be used without polarity changes, for example in FIG. 3, taking the distorted waveform at B and adding a small amount of the undistorted signal A to it results in a more rounded waveform.

The total change in guitar response is more complex than is expressed in steady waveforms; as the input is dynamic so are the interactions. For example, see FIGS. 3 and 4, which only shows the positive swing of a waveform. FIG. 4 is different only in that the guitar is louder, so clean (A) is now larger than distortion (B) resulting in a reduction in overall distortion at C, compared to FIG. 3 ... this may be more interesting if this loud signal now drives an amplifier into distortion.

FIG. 5 shows a differnt take at FIG. 4, with distortion (B) inverted in polarity. This waveform contains considerable clean tone, yet a harsh edge... and becomes more like the example of FIG. 3 (except with output C inverted) when guitar signal is lower.

Operation

The top row of controls are the drive controls. The center position of the drive controls (DRV and FILT) for each distortion is the minimum setting. Turning the drive control right of center produces normal positive drive, while left of center drives the distortion in reverse polarity; either far rotation produces maximum gain. The DRV (drive) control is the main gain setting. FILT (filter) works in tandem and affects the highs only. Turn the FILT control in the same direction as DRV, but slightly less, to produce a flat response. Turn the FILT control more to boost the highs; reduce DRV for even more highs. Turn FILT less or even slightly in the opposite direction to reduce the highs. Turn the FILT knob further in the opposite direction from DRV to produce reduced midrange with strong highs and lows, and to place the highs in opposite polarity from the lows. The drive controls precede their associated distortions in the signal path, and therefore strongly affect the response to the guitar or other source. The Clean signal cannot be altered in polarity, so when combining it with distortion, set the polarity of the distortion(s) accordingly.

The lower row of controls is the mix section. Volume control B is for the Bipolar section, C is the CMOS section, and CLEAN is the clean level/boost. With suitable drive settings, many sounds are available just by adjusting these levels. Also part of the mix section is the FILTER control. This reduces high frequencies of the Bipolar distortion output when turned towards B, and reduces high frequencies of the CMOS distortion output when turned towards C. When centered (there is a detent), little influence on either results.

The various filter responses are different, as suited to the characteristics of the distortion stages. Experimentation is essential to maximum results, however not all playing situations will require the full range of sounds available. Do not hesitate to use the Splonkulator in such situations, and also to use sounds that "underuse" the circuits, because otherwise its flexibility becomes a weakness.

Particularly when experimenting with cancellation sounds, it is useful to learn to "tune" the levels. Here is an exercise: start with C and clean volumes at minimum, and with B set for negative DRV and FILT, and moderate level. While playing softly, turn up the Clean volume slowly. You should first hear the volume decrease due to cancellation, and then begin to increase again. Playing at different volumes will change the point of maximum cancellation. The best setting for a purpose is often not this "critical" cancellation point, but it still helps to be aware of it. A similar tuning exercise can be done with the distortions only. When all three paths are combined with one or more in reverse polarity, things get more complicated, but are still rooted in such interactions. A good sound which uses this interaction is with C in high positive drive and highest volume, B at (necessarily) lower negative drive, and Clean at low level. As input signal increases, C hits full distortion first, then B increases in cancellation -- notching the waveform --, and then the clean level becomes substantial and swings the waveform back in the positive direction.

Example Settings (uses old graphics)

Signal Levels

Either the B or C distortion can be turned up to maximum volume without distorting the output stage: use this fact as a calibration reference. Both distortion volumes at maximum can slightly exceed the maximum output, turn down slightly. The Clean volume control can cause output distortion, since about 20 dB of flat-response boost is provided and no output section has unlimited output (the output level of your guitar pickups will determine the maximum gain beyond which any boost device will distort). The maximum output is about 9 volts peak-to-peak ("rail-to-rail"). This is a better match to pushing the first stage of a tube amplifier into significant distortion than lower output boosters, without the extra trouble of requiring two batteries or power-supply-only operation. More gain, lower levels to the amplifier, and tone changes can be added by mixing in the distortion(s). If other effects are used, high-level boost is normally placed last in the chain in order to avoid overdriving the other effects and deliver full signal to the amplifier. Unusually high output levels can be avoided by keeping the mix volumes set lower (typically below two-thirds), however, allowing placement elsewhere in the signal chain.

The input level capacity is as high as the highest output pickups on the market, but high level boosts connected to Splonkulator's IN may cause adverse sonic effects. When driving the Splonkulator with distortion pedals, most do not have such high output levels, and can be turned all or most of the way up without any issues.

Switching System Information

The standard electronic switching provides a selection circuit featuring no signal interruption, low signal degradation, and consistent output characteristics at all times. "True Bypass" is available as an option as it is also a good system, and is favored by many players. The primary advantage of True Bypass is minimum alteration of the signal path, including unlimited headroom, when bypassed. However, the electronic switching circuit has high headroom, a simple and clean signal path in deselect, and improved transition characteristics that make it worth consideration and the extra trouble of including as part of the design's capabilities. There is no drop-out when switching; the electronic switching has a "soft" switching characteristic which results in a slightly gradualized transition, rapidly cross-fading between the sounds, which avoids a jarring effect when switched (Note, soft switching is not intended for volume switching of high levels in a completely clean environment as there can be some transitional distortion, but in the intended application this is unnoticable -- if this effect was a standard distortion there would be no case of high levels and no distortion). Also, the buffered output will consistently drive long cables (and possibly even reduce noise or lossiness of following circuits due to its low output impedance). Both switching options use a "click" type footswitch as this simplifies circuitry, provides decisive operation, and retains the last used setting.