I totally agree with Mike/trojdor about the modulation on the EQX; since you don't have the ability to adjust modulation on the Equinox, as you did with the CTX, E-Trac, and Explorers, you kind of have to "accept" what you are given by the manufacturer. And what we are "given," by Minelab, with the Equinox, is that the "deep targets soft, shallow targets loud" characteristic on the Equinox is not quite as pronounced as I would like. I agree with Mike, that it's especially the case through mid depths. Once you get down to the REALLLY deep targets, the audio is definitely softer, and you will -- as Mike said -- learn over time what a "deep target" sounds like.
In other words, what you are asking IS do-able, on the Equinox (i.e. to "hunt deep" by sound). But, the decrease in tone volume with depth, is not quite the way I'd prefer; it's not as "linear" as I would like. What I mean by "linear," is that when I ran the Explorer, I ran my "audio gain" at 7 (audio gain being the "modulation" adjustment" on the Explorer). At that setting, it was perfect in my opinion; there was a "linear" decrease in the softness of the tone, with depth...i.e., a shallow coin was loud, a mid-depth coin was progressively softer, and the real deep coins were very soft, distinctive tones. SO, you could glean a TON of information about the depth of a coin-sized target, just by listening. You never even had to look at the depth gauge; the "linear decrease" in tonal volume, with depth, was terrific.
Along those lines, I would not say that you can do this "as well" on the Equinox. It's more "subtle," and less linear. But, the clues are there -- ESPECIALLY on the very deep targets. So, if you are just wanting to listen for the "deep ones," you CAN do that, with the Equinox; I think, in time, you will learn the audio enough to be able to do what you want to do, Capreo…
Steve