Knas Ekdahl Moisturizer

The Ekdahl Moisturizer is a spring reverb, multimode filter and LFO combo unit made by Knas¹. What sets it apart from a typical reverb pedal is that its spring reverb tank sits exposed on the outside of the unit, so the player can use the Moisturizer as an instrument as well as an effects unit: the springs can be played, hit and fiddled with directly¹². It is a mono unit, and it incorporates an LFO that is internally routable to the filter, with external routing options as well².

The Moisturizer was developed with the help of Jason Willett (Half Japanese, Leperchaun Catering), Martin Schmidt (Matmos, Instant Coffee), Joshua Atkins (Polygons, Major Powers) and many others². A later version, the Ekdahl Moisturizer 2, carries the design forward.

What it does: spring reverb with filter and LFO

The signal path combines three blocks: a spring reverb with exposed, playable springs, an analog multimode filter, and an LFO that can be routed to the filter internally or externally¹². The filter is a state variable type with a resonance control that has no resonance limiter, so it can be pushed into self-oscillation territory².

The main controls, as listed by Knas, are:

Because the springs are exposed, the tank works as a sound source in its own right: striking, pressing or dragging the springs feeds physical sound into the reverb path. The maker describes the unit as something the player can use as an instrument as well as an effects unit¹.

One documented user is Jason Glover, featured in a Strymon pedalboard piece, who runs the Moisturizer after all of his dirt pedals. In his words⁵:

He also tweaks the Frequency Cut Off and Resonance controls to thicken everything up⁵.

Power: AC supply, 12V minimum

Power requirements differ between revisions, and this is a common source of trouble with the unit⁴⁶.

R4 and later units are flexible: the power input accepts either AC or DC supplies of any polarity, through a standard 2.1mm barrel connector. The unit requires a minimum of 12V, can theoretically handle DC up to 20V (18V maximum for AC), but Knas advises not going above 15V DC (12V AC) in practice. The current should be at least 0.33A⁴.

R3 and earlier units require an AC output supply at 12V @ 0.33A, which Knas notes are unfortunately not that easy to find⁴.

The classic symptom of feeding an older unit the wrong supply is that all the lights are on all the time, whatever you do⁶. Knas historically shipped American power supplies described as super common: 12 VAC 500mA with a 2.1mm plug⁷.

The unit runs on an external wall-wart rather than an internal supply. Knas wanted an internal supply but abandoned it because of mains liability issues and differences between countries².

Revisions: R3 and earlier, R4 and after

Knas divides the Moisturizer into two families by revision:

The R4 board has all the mod points broken out as one header on the board, which is the main practical difference for anyone modifying the unit⁹. All of the mods themselves are the same as for the R3; the R4 page covers the same ground for the newer board⁹.

Owner modifications

Knas publishes detailed modification guides for both revisions, written for owners with a soldering iron. The maker describes the mods as designed to be as non-intrusive as possible, with no circuit board modification necessary, and beginner-friendly if the instructions are followed carefully⁸. Most of the modifications are, in the maker's words, "scientific", planned with a certain outcome in mind, though some are circuit-bent and were stumbled upon by accident⁹.

The six documented mods for the R3 and earlier are:

A few details worth knowing before starting:

• The original input stage of the Moisturizer (Rev. 3 and 4) allows for 10 times gain. Replacing the 10K resistor R5 with a 1K resistor gives up to 100 times theoretical gain, and lower values give even more⁸.
• The LFO speed is set by capacitor C1, originally 2.2uF. A higher value gives slower speeds, a lower value faster; the mod suggests 1nF for really high speeds or 10uF for slow speeds, on a three-way switch. The replacement capacitors must be bipolar polyester or polystyrene, not electrolytics⁸.
• The resonance limiter mod wires two 1N4148 diodes to RV8 and the resonance potentiometer's outer tabs, with the diodes twined together so their lines point in different directions⁸.
• Rev. 1 or 2 owners do not need the input overdrive mod⁸.

All of the mods require a soldering iron, snippers, 26 gauge stranded wire, a power drill, wire stripper, solder-sucking device, fine tweezers, lead-free solder, tape and pliers⁸. Knas strongly suggests a decent but cheap temperature-regulated iron such as the Hakko FX-888d or Weller WES-51, set to 350C / 650F, or 250C / 500F when soldering switches, and never heating an area for more than 5 seconds⁸⁹.

Buying one from Knas

The Moisturizer is bought directly from Knas. The price is 350 EUR (and VAT if you are in the EU) plus shipping, and the maker takes a deposit of US$90 to buy parts and secure the purchase⁴. Lead time depends on stock: if units are in stock it can be a few days; if a new batch has to be built it can take weeks⁴. Sales questions go through the sales page on the Knas site⁴.

What you get in the package:

• One Ekdahl Moisturizer
• One detachable spring reverb tank in a hard cardboard tube
• One optional American power supply⁴

The hard cardboard tube replaced an earlier padded bag for better protection while transporting the reverb tank⁷. The tank itself is fastened to the unit with self-adhesive velcro, so it detaches for transport². On power supplies, Knas notes that for now they most likely only have American supplies in stock, along with the common EU supplies⁴.

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