The Mainly Tannoy ones are generally the same circuit/original circuit but with decent quality components. I did notice some circuit differences but they're good value for those who want to either do a simple upgrade from the old units or take it further by doing A/B comparison with a more professionally custom made unit. They are upgradable too which is good for some. The sound from the mid-range version I tried a few years ago were surprising and would be fine for most. But the problem that can happen with listening to these old Tannoys (like anything Hi-Fi) is that once you've heard them, curiosity to want more can get the better of you. lol