Recently I acquired a Tone Bender MK2 from British Pedal Company and I copied the circuit to a strip board, I used transistors with the same specs. It sounds practically the same, however, there's simply too much background noise when I switch the pedal On.
Is it maybe because the circuit is not in an enclosure yet and is more prone to interference? This is what a buddy suggested, however, I don't remember this being an issue with other fuzzes I have built, including a MK3 (from a musikding kit) which is actually dead quiet ...
Any ideas?
Well, because BPC are an awful business and make junk.
OP doesn't say the original is noisy, though. There could be cold solder joints or yes, interference and noise being picked up because it's not in an enclosure. Or the transistors could have been damaged by heat from soldering. Or a simple copy error.
Most high-gain circuits are noisy outside of an enclosure, simply because they greatly amplify any noise that may be present ("high gain"...). If you post a clip of the noise maybe we can let you know if it's 'normal'...include knob settings...