of impedance put into the circuit by the transformer that creates the signal for the XLR connector. Because the transformer is connected in parallel across the signal wires, it will always lower the overall input impedance seen by the instrument. The amount of parallel input impedance added to the circuit is directly dependent on the input impedance of the load on the other end of the XLR cable. In summary, as far as impedance goes, this pedal effectively puts the XLR connector in parallel with the ¼” output jack, creating two parallel loads for the instrument. For testing, a 660Hz sine wave at 100 mVrms was used as stimulus. The ¼” output jack was connected to a 98.7 kOhm load, and the XLR was connected to a 612 Ohm load. This combination created an input impedance of 42.1 kOhm, as seen by an instrument. If the XLR connector load was disconnected, leaving an open circuit, then the input impedance seen by the instrument was 71.1 kOhms. Through some math, the impedance of the pedal in parallel with the load on the ¼” jack output is 73.1 kOhms with a 612 Ohm XLR load attached, and 262.1 kOhms with and open XLR circuit. Tuner The range of the tuner is advertised to be from E0 to E5 , which is 20.602Hz to 659.255Hz. The accuracy is listed as +/-2 cents initially, and then +/-1 cent, as the amplitude of the note decays over time. All note frequencies are based off A4 at 440Hz. For this test, a constant sine wave was used as stimulus. Because the sine wave amplitude did not decay, the +/-1 cent accuracy was never initiated. All results were in the +/-2 cent range. During regular use, it may be useful to have the accuracy get more exact with a degrading input amplitude, but to keep consistent test results, the test stimulus must be kept at a reproducible standard level. Through testing, the lower limit that is readable by the tuning circuit is 20.1Hz. Anything lower, and the tuner does not register bass gear 20 FIG. 5 THD vs. Frequency. Output, Input, DI a note. That should be plenty of room to tune E0 , since 5 FHQWVÀDWRQ E0 is still 20.542Hz, which is well within the tuning range of the circuit. There is more headroom on the other end of the scale. At A5 , which is 880Hz, the tuner still provided accurate results. Anything higher than A5 , and the tuner will still read that there is a note, but the accuracy drops off to the point of not being usable. Random notes were selected to check the accuracy of the tuner. The following is a sample of the results from checking notes. E0 , C2 and A4 show in tune from -1 to +1 cents. D#3 shows in tune -1 to 0 cents. A5 shows in tune -2 to +1 cents. All notes tested fell well within the advertised +/-2 cents accuracy. On all tested notes, once the note was showing out RIWXQH�f;RQHUHGOLJKWZRXOGLOOXPLQDWHGLPO\�f;DW¿UVW7KHQ�f; as the note went more out of tune, the red light would come to full brightness and then another light would illuminate. 7KLVZRUNHGWKHVDPHRQWKHVKDUSDQGÀDWVLGH Conclusion This is one seriously sturdy and well-built pedal. Inside and out, this pedal is made to hold up and perform for a long time. The pass-through transformer provides very clean electrical isolation and the tuner accuracy is right where it should be.