Presence/ Depth in circuit vs out of circuit?

[the rossness]

Recently, I decided to take the presence/ density board out of one of my MTS amps. I thought it was broken and was planning on ordering a new one. However, as I played around with the EQ from my preamp, I found out that I really didn't need to have a master section presence/ depth control. I had a Traynor YCS 50 at one point and it had a switch that took the presence/ depth out of the circuit. So my question is, do amps really need this control in addition to their basic EQ? Do any amps sound better without the master section EQ? What can you do with the control vs without it?

Peace~

 

[MississippiMetal]

It depends on how the amp is voiced. Many high gain amps don't fare well without some sort of output compensated lowend punch, because all of the major lows in the preamp have been removed to avoid flabby bass response. Without the depth circuit, some amps can sound thin.

The presence control can help thicken highs and upper mids in an amp that is otherwise thin or fizzy in that register.

I'm speaking chiefly about master EQ controls that work on the principle of negative feedback. Not all global EQ works that way. In the three channel Mesa Recto, for instance, the presence controls for Modern mode are strapped off the master volume and do not operate on the -FB loop like traditional Marshall-style presence.

-FB based global EQ allows you to take advantage of certain frequencies of the amp's negative feedback, whereas without the adjustments the frequency response would be fixed and flat.