A colleague of mine recently handed me their EarthQuaker Devices Blumes, asking if I could take a look.
He told me the issue is a “noisy output”, not the good kind of noise you want from this overdrive pedal. Of course, I was intrigued. The Blumes is known for its warm, smooth overdrive and high-quality build, so hearing it was acting up definitely raised my curiosity.
Visually, the pedal looked flawless. No signs of abuse, oxidation, or physical damage. All jacks, knobs, and switches felt fine. I plugged it in and the problem became obvious: there was a harsh noise floor present even when the pedal when activated.
I opened up the pedal and started by checking the obvious: power supply filtering, solder joints, input/output buffering. Everything looked clean, and nothing seemed to be physically failing. I scoped the power rails next and noticed something strange there was no negative voltage on the main op amp.
The Blumes, like many analog pedals, relies on both positive and negative voltage rails to give op-amps enough headroom for clean and responsive audio. To generate the negative rail from a standard 9V DC input, the circuit uses a voltage inverter IC, the ICL7660. In my case, that chip had gone bad.
I desoldered the suspect chip and dropped in a known-good replacement. The overdrive returned to its usual thick, musical self.
Notes
- read risk disclaimer
- excuse my bad english