A Collaboration Built on Shared Curiosity
Our relationship with Stefan Karlsson from Guitar Pedal X began in the earliest days of RhPf Electronics. When we first released the Mosferatwo, he explored it with remarkable depth. His review helped many players discover our work, and from that moment on we stayed in regular contact. We exchanged ideas, discussed circuits, and talked about the boutique gear industry. Over time he featured several of our pedals, highlighted the Tone Maps, and even covered the Touring Board project.
Again and again, musicians reach out to us and say the same thing. They first heard about RhPf on GPX. For an independent Swiss builder, that kind of support is significant. It has shaped the way our work travels across borders.
Why Stefan Received Mosrawr Serial Number One
When Mosrawr reached its final form, we wanted to say thank you in a concrete way. Stefan’s curiosity, encouragement, advice and honesty have played a real role in our story. Therefore, before the official release, we sent him Serial Number One as a gesture of gratitude for everything he has done for us and for so many other builders.
Furthermore, there is something important to note. Stefan is brutally honest. If he does not like a piece of gear, he will say so publicly, and he will not feature it on GPX. He stays completely independent, free of obligations or pressure, and that is exactly why players around the world trust him. Because of this, the review he later published carries even more weight.
Doom Fuzz Trifecta
In his feature, Stefan placed Mosrawr in what he calls his personal Doom Fuzz Trifecta: he focused strongly on Mosrawr’s voice. He described it as fiercely textured, vibrant and immediately responsive. He also noted how the saturation stays musical even when pushed to the extreme. Moreover, he highlighted how the Low, Bite and Treble controls interact in a precise and natural way, and how the gain structure balances impact with nuance.
One part of his analysis resonated with us in particular. He focused on the scale and presence of the Mosrawr’s texture, noting how the pedal delivers a grand, intense and highly detailed output. This observation aligns with the sonic direction that Silvio from Loopy Demos helped shape during development. Stefan also mentioned that the Mids at noon produced his favourite voice, giving the fuzz a strong and vocal centre.
Recognising the Full Collaboration
Stefan also acknowledged the complete creative team behind the pedal. He mentioned the Mo(s)ghoul lineage, the more aggressive EQ concept developed with Silvio, and the artwork created by Claudia from Sketchy Pedals. Additionally, he appreciated the vintage sparkle pink enclosure that we introduced for this model.
Most importantly, Mosrawr reflects the work of four people. Thomas developed the circuit, I shaped the final direction and production workflow, Silvio refined the sonic vision, and Claudia brought the artwork to life. Seeing this collaboration recognised so clearly means a great deal to us.
Why This Feature Matters
GPX continues to play a central role for gear enthusiasts worldwide. Players trust Stefan because he tests so many circuits, describes everything with clarity, and keeps his platform entirely independent. As a result, his articles introduce boutique builders like us to musicians who may never have found us otherwise.
His Mosrawr feature continues that lineage. It places the pedal within a global context of modern high gain fuzzes, and it highlights exactly what defines our design. Texture, voice, and a MOSFET structure that reacts from the very first note.
We are grateful for his insight, his honesty and his ongoing contribution to the guitar gear community.
Read the full feature on Guitar Pedal X.