Blue Rose is the third installment of repurposed circuit boards.
This one doesn’t actually change that many components, but the changes make a significant difference - I don’t think this pedal sounds much like Fire Fuzz at all, even though it is built on the same circuit board. It is a much stranger sound.
Unlike Fire, this tone control does more than subtle changes. The tone control on Fire is most noticeable on a bass where any changes to treble stand out a bit more because there isn’t as much in the signal to begin with. Blue Rose takes things much further, going from cutting almost all treble to boosting it to the point of strangeness.
Unlike Fire, the way to “clean” it up is to actually stick another dirt pedal in front of it, and then roll the gain knob on Blue Rose down. Because it is gated (it needs a good bit of signal to actually do its thing), boosting the signal before hand will make it less gated.
Another significant difference between this and Fire is the additional switch and knob which controls it. What this does is a bit contradictory and confusing, which is why I typically just say you don’t ever want to know what it does. It is a feedback loop, but because the effect is gated, it doesn’t really create feedback. Because it essentially runs the effect through itself infinitely, it also means the tone control becomes a higher order filter (instead of one filtering stage, there are effectively infinite filtering stages) and so everything the filter does is exaggerated. When you turn this black knob up, the gating element is increased at the same time as the amount of signal fed back into the effect, so on the one hand, it is wanting to just feedback and howl, but on the other, notes get harder to sustain. The result is just plain strange, and I’ve never come across anything like it before. It is a unity of opposites.
While Fire (and most other dirt pedals) respond to different kinds of pick-ups differently, Blue Rose is not subtle about this, especially when in the black mode. The traces of feedback that make it into the signal are set to a different tone in part due to the pick-up used (on a strat-style guitar, that means you can really change how things sound on the fly). Adding another dirt pedal before it will change how that sounds as well, and what each thing will do is not exactly predictable.
And finally, for the real component nerds, compared to Fire, Blue Rose has: two different transistors (both silicon, but one a high gain and the other a low gain one) instead of two silicon transistors of the same build, it has an LED and a Schottky diode instead of a silicon and a germanium one (the center LED is this clipping diode, and it lights up when it is clipping. Softer playing will not make the LED clip), and the resistor-capacitor network that is the tone control has some important values changed. Also, some of the noise filtering components are removed - without these, Fire actually picks up radio stations, but these signals aren’t strong enough to get through Blue Rose’s gate.
All of this together creates an all-around unnatural sound, a kind of fuzz I have not heard in anything else.