The RhPf Electronics Mosphoros is a handcrafted analog overdrive pedal designed and built in Basel, Switzerland, by designer Thomas Besse. It is a fully original circuit built around MOSFET gain stages, and RockBoard's PedalPedia describes its central idea as making gain feel like motion rather than a switch: notes swell, compress, and bloom while staying responsive to pick attack, with a long sweep from clarity to saturated weight instead of a single clipping point1.
The pedal is available now at select retailers and directly from rhpfelectronics.com2.
The controls
The Mosphoros takes an unusual approach to shaping tone: instead of a traditional EQ section, it has three gain-style controls. Guitar.com's Richard Purvis describes the two main controls as gain and output level, with two mini knobs below them that are also gain controls, each raising gain in a specific frequency zone3.
| Control | What it does |
|---|---|
| Drive | Sets the core texture, from transparent lift to natural, organic, amp-like breakup2 |
| Level | Output level, one of the two main controls3 |
| Bass (mini knob) | Increases gain in the low range, shaping tone and texture behavior rather than acting as traditional EQ2 |
| Treble (mini knob) | Increases gain in the high range, shaping tone and texture behavior rather than acting as traditional EQ2 |
Guitar.com sums up the pedal as "a drive pedal that has three gain knobs and no EQ controls," and quotes designer Thomas Besse describing the result as "harmonic mayhem"3. Guitar Pedal X's Stefan Karlsson, reviewing the pedal in March 2026, shared settings he favored: "My current favourite settings are - Drive @ circa 1:30 to 2 o'c, Level @ Noon, Bass @ 2 o'c, Treble @ 10:30 o'c."4
How the circuit works
Under the hood, RockBoard's PedalPedia describes multiple MOSFET stages that interact as the gain increases, with the Bass and Treble controls living inside the feedback path, and a CMOS core with a naturally slower response1. That topology is what produces the swelling, blooming response to pick attack RockBoard's PedalPedia describes, and it is why the Bass and Treble knobs change the character of the gain rather than simply cutting or boosting frequencies after the fact12.
What reviewers said
Guitar.com's Richard Purvis reviewed the Mosphoros in August 2026 and rated it 9 out of 10, praising its smooth amp-like tones and wide gain range3. Guitar Pedal X's Stefan Karlsson, reviewing it earlier in the year, described a touch-sensitive, lively overdrive with fuzz-like dynamics, and reported that the pedal was several years in the making: "Apparently this was several years in the making, and it is the circuit Thomas is most proud of."4
Price and availability
Premier Guitar's announcement of May 2026 gives a street price of $199 USD2. Guitar.com's review lists the price as CHF149/£149/€179/$1993, and Guitar Pedal X's March 2026 review gives $17943. The published figures differ, with the later Premier Guitar figure the higher of the two.
The Mosphoros is a handcrafted overdrive pedal from RhPf Electronics, announced as available now at select retailers and directly from rhpfelectronics.com, with a street price of $199 USD2. It is a wide-range overdrive built around multiple MOSFET stages that interact as the gain increases, with the Bass and Treble controls inside the feedback path1.
A demo video by Alberto Barrero is available in English via the maker's product listing1.
Videos
Philip Czarnecki and RhpF Electronics
Alberto Barrero and RhpF Electronics
Haiko Heinz
Questions
Can the Mosphoros be used as a clean boost?
Yes. Premier Guitar's press material describes a wide output range, saying the pedal functions as a clean boost, a foundational drive, or a primary saturation source. The Drive knob sweeps from a transparent lift to natural, amp-like breakup, so at the low end of its range it can sit on a board as a boost and at the high end carry the distortion role on its own.
What power supply does the Mosphoros need?
The Mosphoros runs on 9V DC, center negative, and draws 10mA according to the maker's product page. That is a light enough draw for most pedalboard power supplies, but as with any pedal of this type it needs a center-negative DC supply rather than a battery.
Who designed the Mosphoros?
The Mosphoros was designed and built in Basel, Switzerland, by RhPf Electronics, the pedal company of designer Thomas Besse. Guitar Pedal X reports the circuit was several years in the making and describes it as the circuit Thomas is most proud of.
How is the Mosphoros different from the Mosferatwo?
Both are RhPf Electronics MOSFET gain pedals, but the Mosphoros is a fully original circuit with three gain-style controls: a Drive knob for core texture plus mini Bass and Treble knobs that raise gain in the low and high ranges rather than working as conventional EQ. The Mosferatwo, announced in May 2025, is the earlier touch-sensitive MOSFET overdrive in the range.
Sources (4)
- Mosphoros by RhPf Electronics, RockBoard PedalPedia, 2026
- RhPf Mosphoros MOSFET Overdrive Debuts, Premier Guitar, 2026-04-07
- RhPf Electronics Mosphoros review, Guitar.com, 2026-08-19
- Guitar Pedal X, Guitar Pedal X, 2026-03-05