Volume control on preamp level = sound difference

I have a question regarding the volume settings on my Cary SLP-05 preamp or for any preamp for this question.

I noted on more than one occasion that it seems the higher the volume setting on the Cary the better or shall I say, more balanced the sound becomes. I also detect more air as well.

Let me explain further. My source unit (Transporter) have a digital volume control. If I remember correctly one should have the maximum output signal to the preamp for the best sound (that's probably where I got it wrong). Sometime back I noted a change in sound in my system. It seemed more relaxed, not in a bad way as it's quite forward now, just easier to listen to. I also noted the volume control way up on the Cary. I was puzzled by this not thinking that someone had turned the volume control down on the Transporter. When I restored the volume to full on (0DB reading) the sound had indeed changed to a livelier more forward presentation.

The other day I changed a balanced cable to a Neotech EI3001 cable and Furutech rhodium XLR connectors. This cable literally doubled the sensitivity of the Cary, that is, I now have the volume control barely cracked to have room filling sound. Of course this cable changed the presentation and in some ways it has become too forward, too dynamic, and air and decay seem to have been lost. This cable is (or was) on the output side of the Cary feeding my Nuforces. I know the cable is new and needs some time on it but I simply couldn't listen anymore and moved it to Transporter feeding Cary. More volume is needed on the Cary now and music, pace, balance and air/decay have mostly been restored. It simply sounds better.

What is going on here?
It takes a lot of signal power gain to go from a laser beam's output to driving speakers. This gain is divided up into a few pieces and each contributes to the overall volume level. One piece comes from your source, then another comes from the preamp, and then yet another (and usually the largest chunk) comes from the amp.

When you have your source's volume turned down, you reduce its share of the gain. In order to keep the same volume level, you need to increase another part: the preamp.

So you can vary the contribution of each piece to the overall gain. When you turn down your source and turn up your Cary, you hear the sound of the Cary a lot more (relaxed and easy). When you do the opposite, the more forward sound is what your source really sounds like (forward and dynamic).

Another point gets back to your volume level question. Most volume controls operate best at full volume - and not only is this true for digital domain but also for analog domain. A volume control is not all that easy to design well.

But I think you are mainly hearing the differences in sound between your source and your preamp. All components have their own "flavor" and you simply prefer the Cary's.