Best Location for Best Cable


I have an all Benchmark system, DAC3B + HPA4 preamp + AHB2 amp + Benchmark speaker cable. I am using Benchmark StarQuad XLR interconnects on all the above components. The HPA4 + AHB2 is separated by about 15 feet so I have either a 15 foot or 20 foot XLR between them. System sounds excellent.

Today, I received my upgraded Audience AU24SE (some XLR’s and some RCA’s, all short) from Audience AU24 and AU24e. I put the AU24SE XLR between the DAC3B and HPA4 preamp and notice a very slight unveiling of the sound. It sounded even more excellent now. I am not even sure if the Audience cables are burned-in because they are upgrades not new (likely burned in).

I am now wondering where the best bang for the buck improvement in cable sound comes from. Is it the sources connected to the preamp or the preamp connect to the amps? I cannot permanently move my gear around anymore since I have committed to my current setup, which I love. I have a new stereo rack coming next week and it is too big to put between the speakers to have the preamp and amp close to each other. I am also not sure if non-Benchmark XLRs would work great sonically for very long lengths with my gear (cost is also a factor).

I am just curious as to where people put there best cables. This info will be useful to see what I should try.
yyzsantabarbara
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Normally I would replace cable closer to source - in this case DAC to preamp, but in your case you can set both cables at +22dBu (close to +24dBu pro standard) and the most obvious difference is cable length.  IMHO, cable always has negative effect on sound (shouldn't be used as tone control) and this effect (capacitance, dielectric absorption, electrical noise pickup) is proportional to cable length.  Since cable between HPA4 and AHB2 is as long as 20 feet I would replace it first.  
If you are running multiple sources, then: 

#1 for me would be preamp to amp in this case.  Multiple sources benefit.

If you are only running ONE source, then:

#1 would be start at the source cable first.  

Ideal is "both".