Like the thread about re-amping elsewhere there seems to be a bit of confusion about the frequency response nature of the (passive) guitar/lead/input device system.
The term "tone sucking" has been bandied a lot and I am going to take the phrase to mean High Frequency loss (and it took me fekkin' AGES before I found THAT out!). Note too that for "HF" we are really talking up to about 8kHz here, 10-12kHz absolute tops, poncey talk of "air" will be stomped on!....If someone means something different from HF loss by that term, please give a definition?
The guitar/cable/amp interface it at once simple and complex!
Simple if you have one pup selected and the volume and tone at max (min attenuation) Then the system simplifies(!) to an inductive source in series with a resistance (of a 1-5kish) shunted by some capacitance and a load R, normally about one meg Ohm*. For any given pup' the response is a flattened peak centred on 2-5kHz the exact frequency being fixed by the inductance of the pup and the cable/amp capacitance. NOTE! From the OP's point of view, if you have a 5mtr lead and chop it to 3+2mtrs the response will not change (well, tiny bit from the extra input capacitance but this is not usually very big) . Note also that a HIGHER lead capacitance can result in more subjective "bite" because you will shift the resonant peak down to a lower frequency that might be more sensitive to the ear( Loudness curves) or indeed a peak in the speaker.
Then, whilst it is true that a lower load impedance, i.e. sub the magic meg', results in less treble, if you insert significant resistance, by cranking down the VC, a lower load will make this LESS apparent. Of course, once you start Jodrelling about with pots, things get very electrically complex. For home recording there is a very great deal to be said for having a buffer as the first thing the guitar output hits because after that you can do pretty much WTF you like.
Pedals and AIs generally have a very low input capacitance, much less than the 150puff or so of the typical triode input so a Y cable is fine. However I much prefer to put 3(or more) jacks in a wee tin and wire them pin for pin. Not only to I find this a more "elegant" way to split but the box can be used for other duties, speaker paralleling for example.
With SO many pickup regimes, so many cables and cable lengths and so many amps/pedals and speakers, no wonder this area is all pretty much "cut and try"?
*Many AIs, especially the early ones, had a Zin well under 1meg, some are as low as 100k. Nobody has ever seemed bovered tho' but!
Dave.
I'm just mulling over the revamp my 355 is due for. (.. ID the split Duncans I put in years ago to look at shifting the tone a bit, replace pots and jack, and thinking about those tone shifts with volume pot' alternatives.