I get a feeling that John East's U-Retro series isn't always 'flavour of the month' on TB compared to Aguilar, Bartolini, EMG etc. I've fitted and had already installed models of all these pre amps as well as having a whole lot of experience with the John East produced ACG filter based pre's.
In fact if I spent as much time practicing as I do fiddling I could be quite a good player
John, as well as being an exceedingly nice guy, is very clever and he designs his circuits with a great amount of consideration i.e. they aren't just simple boost and cut pre's. He even uses active blend circuitry to overcome the limitations of passive blend.
I've no connection with the guy commercially but I'll always big up his work, including the ACG pre's based on experience.
I've heard comments that when the treble is boosted they can be noisy. All I can say is that at max treble on my NS5 there is total and complete silence
I just love the ability to boost the mids at a little above the lowest frequency setting and leave the bass and treble flat, clear, growly aggressive in yer face bass that cuts through like a hot knife through butter
And the ultimate knob 'bling', gold on black (the 2 switches are tucked away in the cavity defaulted to active and active blend)
I will give the HazLabs 9v cut and boost on the new bass a really good chance to prove itself but don't be surprised if another U-Retro gets fitted
Peter