The Klein Bottle was designed for the noise makers, soundscape artists, endless tinkerers and tone wizards. This epic pedal starts by splitting the input signal into three FX loops, each with dedicated controls for pre-gain, HPF/LPF (bandwidth filters), and mix level. The magic happens when you use the six feedback controls to send the signal from one FX loop into another...and then back again! Keep your existing tone intact with the DRY knob, while layering a cornucopia of sonic goodness on top.
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Navy + White Text graphic
Teal + Kelp Forest graphic
INPUT (right side):
OUTPUT (left side):
The input impedance is 1M-ohms (unbalanced), so it will work great with any instrument, whether passive or active.
The unbalanced output can drive loads as low as 400 ohms without tonal coloration.
The circuit was designed to play nice with whatever you plug into it, but we do recommend using an 18V power supply when using the pedal with active instruments (such as a synth).
Powering the Klein Bottle at 18V allows it to handle louder signals without adding distortion, often resulting in the loss of bass frequencies. If you plan on plugging in a synth or going wild with self-oscillation, you will get the best results when using an 18V power supply.
Sets the overall volume of the Klein Bottle, when active.
Due to design constraints when building a complex & compact circuit, the master knob is technically still active when all 3 loops are in bypass. A dual-gang pot was used to design a circuit that will stay a unity in bypass no matter how you set the master knob, but you will notice a change in the noise floor (especially if you crank it).
In general, it is recommended to start by setting the master control lower (between 9:00-11:00), and then use the PRE/MIX controls to set your overall volume. The master can then be used to make quick volume adjustments as you adjust various settings.
Sets the corner frequency of the HPF (high pass filter), from 33Hz (fully counterclockwise) up to 3.3kHz (fully clockwise). A higher corner frequency = more bass cut
Sets the corner frequency of the LPF (high pass filter), from 230Hz (fully counterclockwise) up to 23kHz (fully clockwise). A higher corner frequency = less treble cut
To open up the filters for almost no tonal coloration, turn the HPF fully counterclockwise and LPF fully clockwise.
There are internal trimpots to set the makeup gain between each HPF & LPF. If you plan to use the loops as a 3-way crossover, push up the makeup gain to compensate for the volume loss of multiple, aggressive filter cuts.
Middle = no trails
ALL = Turning an effect loop on/off only turns on/off the input to that effect loop from the input. The feedback loops and the return from the loop remain active. This allows time-based pedals to decay naturally when bypassed.
SENDS = The FX loops remain active at all times. You can activate just one loop, but still feed that loop into the other two (and back again).
Due to design constraints when building a low noise circuit that ran on an industry standard 9-18V power supply, the signal to each effect loop has some bleed in ALL mode. This is one aspect of the Klein Bottle that I continue to research, and if I find a simple solution, I will share it openly.
Sets the volume/gain level going out the send of the FX loop. Push it up to either add gain/distortion to a drive pedal or to makeup gain from aggressive filter cuts.
Sets the volume from the return of the FX loop going to the output of the Klein Bottle.
If the pedals in the FX loop are not adding gain/volume, it is recommended that you set mix levels rather high (2:00-4:00) to allow the PRE & MASTER knobs to optimize the amount of clean headroom & noise floor.
There are 3 internal trimpots to set the brightness level of each LED light.
Sets the corner frequency of an all-pass, phase shifting filter. Counterclockwise = no phase shift, clockwise = 180 degree shift across the audible spectrum (inverts the signal).
To learn more about how all-pass filters work, click here.
Sets the volume of the dry signal, unfiltered from the input, into the main output mix.
Due to design constraints when building a complex & compact circuit, the dry knob is technically still active when all 3 loops are in bypass. However, it has been shunted to ground with an optocoupler. Because an optocoupler can't reach zero ohms of resistance, a tiny amount of bleed comes from the dry path. You can hear it in bypass if you crank up the dry signal, but even then it just makes the bypass signal a bit louder.
ONE, TWO, THREE:
These rugged Carling switches turn on/off each FX loop.
Each footswitch has a "hidden" DualMode feature. Pause 3 seconds and then enter this sequence - press + press + hold (until light blinks) - and you will have changed the operation to momentary mode.
In momentary mode, the loop is active only when holding down the footswitch. As soon as you release it, the loop turns off. Try it with trails active and a delay/reverb effect to quickly bring in ambience on specific notes/chords/riffs.
To return to standard latching mode, pause 3 seconds and use the same tap + tap + hold sequence. All switches default to standard operation when the Klein Bottle is first powered on.
6dB / 12dB:
1to2, 1to3, 2to1, 2to3, 3to1, 3to2:
Sets the steepness of filters. Use 6dB for more modest EQ cuts, and use 12dB for more extreme cuts (or if using the pedal as a 3-way crossover).
For example, if the LPF has a corner frequency of 1kHz:
6dB: -6dB @ 1kHz, -12dB @ 2kHz, -18dB @ 4kHz, etc.
12dB: -12dB @ 1kHz, -24dB @ 2kHz, -36dB @ 4kHz, etc.
The middle position creates a 12dB/octave HPF and 6dB/octave LPF.
These 6 controls set the amount of signal that is fed from the return of one loop directly into the send of another.
For example, 2to1 sets the amount of signal going from the return of FX loop #2 to the send of FX loop #1.
These feedback loops do not pass through the filter sections.
Sends the signal out for external processing. The send is fed by the PRE control and two of the feedback controls.
For example, the send to FX loop #2 mixes the signal from PRE #2 and feedback controls 1to2 and 3to2.
Returns the signal back in to the MIX control and two of the feedback controls.
For example, the return from FX loop #3 sends its signal to MIX #3 and feedback controls 3to1 and 3to2.
Click the pedal to learn about each control.
How it Works
The final mix stage blends the three FX loops and the dry signal taken straight from the input buffer.
The FX loop mix outputs are always on when the trails switch is set to the "ALL" position, and only the input to the FX loops turns on/off in this setting.
After the signal returns from the FX loops, it hits three controls. Two of these controls feed the signal back into the send of the other effects.
The controls are named by what return they come from, and then what send they go to. The control "3to2" sets the amount of signal fed from the return of loop 3 into the send of loop 2.
Self-oscillation is very possible, so be careful not to kill your ears when using the feedback loops!
The Klein Bottle starts with a high impedance, unity-gain buffer. This is necessary to split the signal in the next stage without loading down the sound source.
Unlike all other VFE Pedals, the Klein Bottle is not true bypass. The full features of the pedal would not be possible with smooth on/off switching without using CMOS switching along with an input buffer.
The signal is split into four pathways. Three head into identical HPF & LPF bandwidth filters, with an internal makeup gain stage in between. These filters have a wide range - 33Hz to 3.3kHz for the HPF, and 230Hz to 23kHz for the LPF.
Use the filters for moderate EQ changes or to limit the bandwidth to a smaller range of frequencies. Set the 3 filters up as a 3-way crossover to send each part of the signal through different effects.
After the filters, the PRE knob sets the volume of the signal send into the FX loops.
The sends mixer also receives signals from the feedback loops.
Click on the diagram to learn more.
Enclosure dimensions: 6.2"W x 5.0"L x 2.2"H (158 x 127 x 56mm)
Shipping Weight - 2.5 lbs (1.1 kg)
Industry-standard 2.1mm, negative-tip DC power supply.
STANDARD - accepts 9V up to 18V (recommended)
STANDARD ~80ma @ 9V, ~150ma @ 18V
BY THE NUMBERS:
5 OP AMPS
4 INTEGRATED CIRCUITS
1 CIRCUIT BOARD
The Klein Bottle was an evolution of an idea that first came to me and my brother Joe independently in 2011. We imagined a pedal that could split the guitar signal into bass, mid, and treble frequencies, and then run into separate distortion circuits. The first iteration of this idea came with the Triumvirate, and then later the full concept was put into the RUP multiband distortion.
The big lesson I learned from the RUP was the power of using the FX loops to insert other pedals to create unique FX combinations. At the same time, I was designing a delay pedal under the name "Klein Bottle" that would allow the user to feed three delays into each other - creating an analog way to have the user create a reverb-esque soundscape. After designing a working prototype, I quickly realized that the cost to manufacture would be too great to bring to market - and that the real power still lied in the FX loops.
It took a couple more years to finalize the design, but the removal of any internal effects allowed the pedal to do so much more (and cost less to build). It combines both the bandwidth filters of the RUP and the feedback controls of the delay-based first prototype.