version 6/7/2006

Subzombie TM Fuzz/Distortion Device Owner's Manual

Connection
Connect Guitar or other Instrument to IN/POWER jack -- this also powers up the unit when using batteries, so remove this plug when not using.
Connect OUT jack to amplifier. May remain connected.

Observe all safety warnings with regards to external equipment.

Battery Installation
Battery is 9 volt type: US "9 volt"/International "PP3"

Remove 4 screws from bottom of enclosure. The battery goes in the lower corner of the enclosure between the footswitch and the OUT jack and connector clip best faces the corner. Reassemble carefully -- do not cross-thread or overtighten screws. The cover go on either direction but the edges will align better in one way: note the markings on the inside of the cover.

A power adaptor with negative tip, positive sleeve (industry standard) may also be used. This must provide regulated voltage (i.e. be for quality audio applications, Boss or equivalent) not exceeding 15 volts.

Operation: Basics
Three seperate distortion signals are produced within this single device for a powerful means of altering the distortion characteristic.They are labelled D1, D2 and D3, in order of increasing distortion increments. An essential feature is that the middle level distortion generator (D2) is reversed in polarity, allowing highly distorted "fuzz" type sounds to be created using smoother sounding distortion generators as building blocks. Three LED indicators on the front panel show the progression of the level of distortion.

The MIX control is the main determiner of the sound characteristic. Starting in the center, you can go either left or right for two versions of the same type of variation. On either side, a "critical" region is found where the in-phase components (D1+D3) cancel partially against the out of phase one (D2). In other words, the sound whacks out. This is marked "Z" and also "G" (see below). The left side enphasizes the lower distortion D1 in volume but D3 still has more gain, which tends to balance them into a mixed sound. The right side emphasizes the higher distortion D3 and uses D1 to clean the attack and balance out the sound. At "+D1", "+D2" and "+D3" a corresponding one of the distortions is dominant, but all settings are still mixes and the +D1 and +D3 positions are pre-set mixes of D1 and D3 (the lesser about one third the level of the louder). Meanwhile the +D2 range controls a shift between D1 and D3, the two in-phase signals each low level but combining to still be audible.

The HI control also contributes to the BLEND interactive to MIX. It cuts highs of one of distortions D1 or D3 as indicated by the "-D1" and "-D3" markings. The center position is the start point and results minimum alteration of the sound. At a MIX of +D1 or +D3, or nearby, the highs are smoothed in two different ways by turning HI to either side and treble is reduced somewhat overall. At most other MIX positions overall treble tends to be boosted by the action of HI. With the MIX control in a critical position the action of HI becomes very dramatic. After turning HI more to either side for a particular MIX, try turning MIX a little more to its side to further explore related sonic territory such high cuts or a midrange notch.

The GAIN control adjusts the amount of distortion and sensitivity. It is centered on crossing the dynamic threshold where the three distortions are most different and provide a "vocal" emphasis. Lower settings shift this emphasis into the attack of notes, and high settings go "over" the dynamic threshold into either complete turbulence or smoothness with a "swell" effect on sustained notes. Also, the far counter-clockwise setting (BCUT) cuts bass for articulation beyond mere low gain (LO or above).

VOLUME is used to match the volume to the bypassed sound and compensate for changes in volume due to the other controls. It also changes the tone somewhat in accordance with the internal TONE trimpot (see below).

The BRAINS footswitch enables the effect.

How It Works
A parallel mix of three distortions may be produced simply by using a cascade (series) configuration:
                               

The example to the right shows graphically a simplified example of how distortion mixing works to produce a fuzz sound. "A" is the positive portion of a distorted wave. "B" is more distorted (more gain) and inverted (upside down). "C" shows how these add together, forming a harsher, more complex waveform. Or rather, B subtracts from A by its magnitude. This still only hints at the complexity. For one thing, Subzombie uses three distortion signals with gradually increasing levels of distortion and the middle level is inverted (reverse phase or polarity) whereas the lower and higher level of distortion add together in phase. Perhaps more important, the differences between these distortions change dynamically, for example at some point the lower distortion signal is clean, while the higher distortion signals are slightly distorting.

But waveform analysis is a limited way to understand how this sounds. Essentially, when you subtract a cleaner signal from a more distorted one, you subtract the cleanness and leaves only distortion. The various signals cancel, oppose, or "fight" one another and sounds like it, due to the more jagged waveform. Also it can sound like like the higher distortion subtracts distortion from the lesser distorted signal, making a clean signal mixing with a totally distorted one, when not one of the individual distortion signals are completely clean or completely distorted. A wide range of sounds may be acheived by the proper controls when the distortion elements start out fairly smooth sounding by themselves. Using three distortion levels further complexifies the sound but also helps balance the characteristics from being only extreme. Subzombie's mix control also provides simple in-phase mixing to be emphasized at the +D1 and +D3 positions. A further advantage of distortion mixing is that the distortion characteristic can be caused to vary with frequency by altering the frequency response of one distortion source relative to the others, producing a nonlinear filter. This also has a conventional tone control side-effect.

Controls: More details
The D1 LED works differently than D2 and D3 because the D1 distortion generator produces most of the gain and increasing levels of distortion. The D2 and D3 stages only contribute additional distortion and their LEDs only indicate that addition. D3 illuminates with the least input level and gain because the D3 distortion generator has the most gain in combination. When the distortion level increases to illuminate the D2 LED, then D3 ceases to become much brighter, and likewise with D2 vs. D1. But, the D1 LED must be much less sensitive. When the distortion increases enough to first light D1, the D1 LED lights at a level so low it is all but not visible, but the D1 stage is is not limited by preceding distortion stages and its LED continues to get brighter with increasing distortion. At maximum gain and with a high input level, the D1 LED becomes brighter than the D2 and D3 indicators.

GAIN also cuts bass at the highest settings. This is not noticable in the way the BCUT setting is because there is still a lot of bass gain and the cut usually only prevents muddiness. At all medium settings the pre-distortion frequency response is wide bandwidth and uncontoured.

The critical regions of the MIX control are marked "G" for a Gate point where cancellation is strongest for clean signals, and Zombie point "Z" where cancellation is strongest when distortion is maximum. These points are very close together on the left side but well spaced on the D3 side. The control position markings are approximate but closely spaced scale markings are provided to aid repeat settings.

With increasing deflection of the HI BLEND control, the stronger attenuation progresses towards higher frequencies, with a full low-pass response at maximum. Frequency also shifts upward as +D1 and +D3 MIX positions are approached and turning MIX and HI both far in the same direction causes a rolloff of all three distortion signals. -D1 always affects D3 somewhat and vice versa. All blending is dynamically affected, varying with GAIN and input level.

The brightness of top status indicator provides a crude indication of the strength of the battery. The D2 and D3 indicators are NOT affected by battery strength except when complete battery failure results. It may be helpful to compare the brightness of these indicators.

The internal TONE trimpot and VOLUME
VOLUME also changes the tone somewhat in accordance with the internal TONE trimpot. A VOLUME control position slightly above midpoint results in the most bass enhancement. The louder MIX settings match to the clean sound with a low VOLUME setting, but fuzzier, brighter mixes are quieter and therefore result in VOLUME settings with more bass enhancement. The highest VOLUME settings result in less bass enhancement as is appropriate for volume boosting or driving an amplifier into increased distortion. TONE calibrates VOLUME depending on if a balance with the bypassed sound is desired or if it preferred to use the Subzombie for sounds that "cut through" more, for example when driving into a dark sounding or distorted amplifier.

The TONE trimmer is a small potentiometer located on the circuit board (see battery installation instructions above to open the unit). Note: this control is delicate and therefore, if you do not feel comfortable with your ability to adjust it, it is suggested you leave it alone. Some force and a small screwdriver will be needed to turn the control, but do not apply excessive downward force as this may break the control or excessive rotational force as this could break the "stops" of the control. Subzombie is normally shipped with the control near center so it should initially be able to turn in either direction.

The "knob" on the trimmer is a black circle with a screwdriver slot in the center. Turning it clockwise increases the action of the control and counter-clockwise minimizes it. Its action is to increase the relative amount of bass by reducing to volume of all other frequencies when the VOLUME control is set to a middle setting. This also improves the "taper" of the VOLUME control response; setting the TONE control too far clockwise, however, will cause a "flat spot" in the VOLUME control taper where there is little change in volume (except bass level) between the 9:00 and 1:00 positions. Increased TONE settings cause the response shift to extend higher in frequency but still level off, but the full clockwise position will completely eliminate high frequencies.

Signal Characteristics
The input is designed for high output pickups, but high level boost devices connected to Subzombie's IN may cause adverse sonic effects because the first stage is a medium-level boost stage. It may also then become impossible to match levels. When driving the input 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. Best signal-to-noise ratio is achieved when the guitar volume is set to maximum, although turning down the volume to intentionally change the sound is very effective.

The maximum output level is generous, but volume is reduced with many mixes. These tend to produce a "spiky" shaped waveform with a higher peak level than the apparent volume may indicate. The output is wide-bandwidth rather than sharply filtered to smooth the sound like many distortion pedals, to increase versatility. There is some filtering, but this is aimed more at making the signal easier to amplify than audible results within the range of most guitar speakers.

TIPS
Start with a clean amplifier setting, at least until you get more familiar with the controls.

If you play a string while adjusting to "tune" the mix, use enough gain, but then try turning down the gain some for actual playing.

To find a Gate point, turn up the gain but turn the guitar down. Adjust the MIX for least noise. The strongest gating occurs with HI centered, but gating over a limited frequency range is also possible.

To find a Zombie point, turn up the gain and play a string loudly. Adjust the MIX for buzziest sound. Try this with with HI centered, and then turn HI to 9:00 or 3:00. This will increase treble due to strongest cancellation in the bass. Then turn MIX farther to the side slightly to move the strongest cancellation to the treble, reducing it. From this point, HI can be turned farther to its side to cause a notch filter response.

The only problem with the most extreme settings is that they are, well, extreme. The first step is to learn to tune them, the second is to learn to detune them.

Be sure to try your guitar's TONE control.

Combinations
Subzombie is an excellent building block towards more complex sounds due to its controllability and capabilty to be sonically neutral. An equalizer following its output is a natural combination which allows more bulk tonal flexibility and the fuzz's settings to be manipulated independently of final tonal contour. Distortion devices and amplifier distortion can also be stacked; a big advantage is that lower gain settings can be used for each box. Distortions that limit the dynamic range too much will produce poor results driving SZ's input -- overdrives work better in this position. Note that distortion is only part of many boxes' sound, they may contain strong tone shaping EQ and filtering; this can be useful or problematic. Some distortions may work well following SZ when set to low gain because they smooth the sound. Tube-based distortions and amplifiers are also a natural combination as they add that certain quality. Compressors driving the SZ input are surprisingly effective, with their attack time controls becoming more powerful.

MODS/REPAIR
The OP-amp ICs are are socketed for easy replacement and this also allows experimentation. Replacement of the first IC (nearer the input) also can allow higher power supply voltage to a maximum of 21V, although improved sound is unlikely. This does not automatically void the warranty but mistakes are not covered. Soldering does void the warranty. A possible mod is to increase the output filtering capacitor. Easy method: a cap across the VOLUME control's outer legs will parallel to the internal .0022 uF cap. This reduces the low-pass filter's cutoff frequency, but not consistently at all settings.