If for a publication, and if you are comparing A to B, then you ought to keep everything else constant, like you said. If it’s for yourself, then there are no rules. Because you own all the gear, and you would have a sense of how each piece contributes to the total SQ. So you, better than any third party, would be able to assess the effect of a single component, by moving it from one system to another. Also, you don’t have to put your opinion into words; you can do it all in your head and with your own senses. I have 5 turntables and two completely separate audio systems. By moving cartridges and tonearms around, I have learned a lot about interactions, how a cartridge can be mediocre in one tonearm in one system and then sound exceptional in another setting. But I wouldn't foist my findings on anyone else, except as a casual observation.
TESTING DIFFERENT DECKS AND ARM COMBOS
Just for discussion purposes I am posing this.
Many people that review - nay almost everyone - says that when testing a component against another you do a direct comparison without changing a thing save that component therefore same everything but the cartridge or tonearm.
I have wondering if this is a bad approach or not as I am contemplating a bake off at home. My EMT is optimised for an EMT 929arm and EMT cartridge; Amazon Model One Transfiguration; JVC QL10 (not sure but i reckon good mm so Pickering XSV4000); Townshend Rock (london decca - sadly not got one)
My rationale is that lets say you race a car rounda track you don't put Porsche 911 tyres (including the wheel and tyre) onto say a mercedes CLK - yes it will work but it is not optimised.
I am not a reviewer - but that said I think the whole front end optimised approach is the best. What say you and why?