Klein Bottle v2

Description

The was built in the last batch of just 8 version 2 Klein Bottles. These used the OPA1644 op amp on the front end to lower the noise floor for passive instruments. It combines the ultra-low noise OPA1604 chip used in the FX loops for the lowest noise floor possible. More details about this change can be found at the bottom of this listing.This Klein Bottle was built with a "Chocolate" paint finish and an ant farm graphic hand-painted by my wife. This is the only Klein Bottle made with this graphic. The knobs alternate from silver to a darker gray to visually separate the controls for each FX loop.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.Version 2 brings greater headroom, reduced signal bleed, improved switching system, phase switches on each channel, and a feedback system that is easier to dial in. PRE - Sets the volume of the signal going out each FX loop.MIX - Sets the volume of the signal going back into the final mix.HPF - Sets the corner frequency of a 12dB/octave high pass filter. Turn this control fully counterclockwise to flatten out the bass response. This filter is before the loop.LPF - Sets the corner frequency of a 12dB/octave low pass filter. Turn this control fully clockwise to flatten out the treble response. This filter is before the loop.LOOP X - Sets the amount of signal sent from one loop's return to another loop's send. The number specifies which loop is receiving the signal.0° / 180° - Phase inversion switch to correct (or create) phasing issues.MASTER - Sets the overall output of the pedal.DRY - Sets the amount of the original, dry input signal fed into the final mix.TRAILS - This toggle switch selects what parts of the circuit remain on when an effect is turned off. Set to "SENDS" to keep all the LOOP X controls active at all times. Set to ALL to have both the MIX output and LOOP X controls active continously. The middle position turns off everything connected to that loop when not active. In all positions, the LOOP X and MIX controls remain active when you hold the footswitch down, allowing for more natural decay of time-based effects.MAKEUP - Internal makeup gain trimpots to adjust for how you use the HPF/LPF section. Increase gain for more output from the PRE knob, decrease gain to reduce it (or increase headroom).IMPED - Sets the input impedance of the Klein Bottle. Set to about 1M-ohm by default, which is great for a variety of passive instruments. If you use exclusively active instruments (like synths), input impedance can be lowered to reduce the small amount of thermal noise that comes from this resistance (which can build up after multiple feedback loops).LED - Internal makeup gain trimpots to set the brightness of each LED. More details about the OPA1644 modification:I regularly experiment with different ways to lower the noise floor in my designs. I have a degree in mathematics, so all the electric engineering knowledge I have learned has come through experimentation and research. It seems every couple of years I learn something new. For the version 1 Klein Bottle, I learned all about Johnson-Nyquist noise in resistors - and immediately employed that knowledge to make the pedal quieter. In version 2, the key discovery was about parts that could do a better job with the switching & power systems. This summer, I learned that the impedance of a sound source has a sizable impact on noise, and that a bipolar op amp with lower noise specs may actually be noisier than an FET op amp with high impedance sound sources, such as an electric guitar.When I designed the latest version of the Standout mid booster, I tested multiple op amps and found that the OPA4134 (FET) performed better and had less noise than the OPA1604 (bipolar), even though the OPA1604 had much better noise specs on paper and had performed better in the version 1 Klein Bottle prototypes. Now I know why! What I didn't know until just a few weeks ago is that the the OPA1644 is best of both worlds - it's an FET-based op amp with super low noise specs (in fact, I'm building a batch of Pinball/Standout v3 pedals with it right now). I added it to the front end of the Klein Bottle, and I could immediately hear a difference in the noise floor when connecting an electric guitar. I wish I had known about this chip a years ago, as I would have made it standard in all my Klein Bottle builds. While the other Klein Bottles use low-noise chips, I am always looking for ways to lower the noise floor, and I'm so thrilled to have found a chip that takes it to the next level.This OPA1644 is the only modification made to the pedal. It only changes the chip that contains the main input stage. The OPA1604 is used for all FX loops, as effects pedals typically have much lower source impedances than passive electric guitar pickups.

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