One Control Minimal Series Tuner MKII with BJF BUFFER

The One Control Minimal Series Tuner MKII with BJF BUFFER is a compact pedal tuner with a buffer circuit built in, made by One Control. The idea is that a tuner sitting at the front of a pedalboard should not just read pitch but also keep the guitar's signal strong on the way to the rest of the board, which is why One Control describes it as "the tuner that realizes all of these" and points out that "it also has a built-in BJF BUFFER that can be active or passive"¹. It belongs to the same family as the standalone One Control Minimal Series BJF Buffer and the One Control Minimal Series Pedal Board Junction Box with BJF Buffer¹².

The BJF Buffer and what it does to your signal

The buffer is the work of Björn Juhl. One Control introduces him as "one of the greatest amp and effects designers" and says the circuit was "created at the request of many of the world's greatest guitarists"¹. On the page for the standalone Minimal Series BJF Buffer, the company explains the reasoning: "Björn Juhl from BJFe designed this buffer to help with the varied cable lengths and true bypass pedals in the signal chain"². In practice, a buffer at the front of a board drives the cable capacitance and pedal inputs that would otherwise roll off the top end of a passive guitar pickup, which is why buffer pedals as a category exist; see Buffer Pedals for how they compare.

The impedance figures are the concrete part. With the BJF BUFFER engaged at tuner bypass, the pedal presents an input impedance of 500KΩ and an output impedance of 60Ω or less¹. The same 500kΩ in / 60Ω out figures appear on the Minimal Series Pedal Board Junction Box with BJF Buffer with the buffer on⁴, and the 500kΩ buffer-on input impedance also shows on the Minimal Series Mosquito Blender Expressio with BJF Buffer⁵. A high input impedance like 500kΩ is what keeps a passive pickup from being loaded down; a low output impedance is what lets the signal drive long cables and downstream pedals without loss.

One detail worth knowing: the input impedance changes with the tuner's state. When the tuner is ON, the input impedance is 1 MΩ¹.

Tuning: range, calibration and the display

The MKII tunes across E0 (20.60Hz) to C8 (4186Hz), which covers everything from a low bass E to the top of a standard piano's compass, and it works in 12 note equal temperament¹. The reference pitch is adjustable with the CALIBRATION button, which One Control describes as setting "the calibration (standard pitch for tuning, center A sound of piano = A4) in the range of 436 to 445 Hz," with 440Hz as the factory setting¹.

The display works on two levels. The maker states it uses "a two-level display system to achieve an accuracy of ±0.5 cents"¹, and the in-tune light is the coarser confirmation on top of that: "'In tune' (the center of the display lit) indicates that you are exactly within ±2 cents of pitch"¹. So the meter shows fine movement while the lit center tells you it is time to stop turning the peg.

Power, size and availability

The pedal runs on a DC 9V adapter with a center minus pin and a 2.1mm inner diameter barrel, drawing a maximum of 40mA¹. That current draw is high enough that a low-output daisy chain output may not be comfortable sharing with it, so a dedicated adapter output is the straightforward choice. The enclosure measures 94D x 44W x 47H mm including protrusions and weighs 234g¹, which puts it in the small-footprint territory the Minimal Series name implies. RockBoard's PedalPedia entry lists the circuit as analog and carries a link to the English manual³.

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