I do not think it works like this - at least in most decks. If I understood correctly.
If meaning that in chain of decks tape 1 would have the original input signal, but instead of that same signal going thought output to 2nd deck, you'd get actually signal of the recorded tape itself? I doubt it.
It seems that it is actually pretty rare function to begin with, that one has option to even select tape recording level monitor display recorded signal level, instead of input signal level. I have had such decks only couple of times. That is very good function, though. To be able to monitor how loud signal actually gets dubbed to tape, instead of just monitoring input signal volume. How loud material ends up on tape, depends vastly on quality of tape.
Anyways, I have had up to 6 decks in chain. Including both, double decks that record both tapes same time and single decks. I have nowadays 3 deck chain. Modest differences on timbre appears never to be related on what number in the link they are, but only the quality of deck itself. Like now, One signal in, decks 1 and 3 gives pretty much perfect sound, deck 2, in middle of them, has notch darker sound. Not bad, not defect, but just all the crispiest high frequencies are not as sharp. It is loud and strong nevertheless. This quality of 2nd deck has no effect on signal going to 3rd deck. Of course, it is not straight line, but signal goes through something in deck I guess. But no audible difference where it could be noticed from dubbed tape. You'll rather notice quality of tapeheads and tape itself, than is there any difference in input signal.
There are available also signal splitter boxes. I used to have this for VHS purposes, but I recall it also had audio functions. It was box of 1-signal in, 7 cables out to recorders. So this is way to avoid chaining from deck to another, if you just have the booster&splitter professionally made for this exact purpose.
All one has to do, is tweak the input volumes to result same volume for each deck and I tend to proof check every tape I dub. Quick listen on both sides that sound quality and volume seems consistent. This way also any emerging problem will be noticed before it results defect dubs...
My experience shows that no matter how nice looking, brand new factory rack model stuff would be stuff like Tascam decks, they are shit. For dubbing purposes. Pretty much and 90's 2nd hand consumer level deck provides better sound than those new Tascam "studio decks".
