software

when an amp has a presence dial, whats that do?

It basically lets higher frequencies pass through in the sound. So you sound is more trebly and more present on high settings. With it set low you sound can get more muddy or more bassy on lower settings.

It's basically an EQ control for ultra-high frequencies (higher than treble).

Presence is a treble control at the poweramp rather than the preamp. Most amps are negative feedback (NFB) amps, which means they feed a smallish inverted signal back to the phase inverter to lower the poweramp gain, which reduces the boominess, looseness, and midrange frequency hump that freewheeling non-NFB amps can have. The presence control shunts the highs out of the NFB loop so that they have more gain as they go through the poweramp. Resonance controls stop the low end frequencies going through the NFB loop, which give them more gain as they go through the poweramp.

(and FWIW, I do like non NFB amps for some applications, just a different flavor than NFB)


Originally Posted by chillPresence is a treble control at the poweramp rather than the preamp. Most amps are negative feedback (NFB) amps, which means they feed a smallish inverted signal back to the phase inverter to lower the poweramp gain, which reduces the boominess, looseness, and midrange frequency hump that freewheeling non-NFB amps can have. The presence control shunts the highs out of the NFB loop so that they have more gain as they go through the poweramp. Resonance controls stop the low end frequencies going through the NFB loop, which give them more gain as they go through the poweramp.

(and FWIW, I do like non NFB amps for some applications, just a different flavor than NFB)Now that's an answer! Deep understanding, and a concise explain,


Originally Posted by chillPresence is a treble control at the poweramp rather than the preamp. Most amps are negative feedback (NFB) amps, which means they feed a smallish inverted signal back to the phase inverter to lower the poweramp gain, which reduces the boominess, looseness, and midrange frequency hump that freewheeling non-NFB amps can have. The presence control shunts the highs out of the NFB loop so that they have more gain as they go through the poweramp. Resonance controls stop the low end frequencies going through the NFB loop, which give them more gain as they go through the poweramp.

(and FWIW, I do like non NFB amps for some applications, just a different flavor than NFB)

And many people think the famous tone of a AC30 it's because works in class A and a big part comes from the fact it doesn't have a NFB.


Originally Posted by BreoganAnd many people think the famous tone of a AC30 it's because works in class A and a big part comes from the fact it doesn't have a NFB.

Actually, the AC30 is Class AB but you bring up a good point that its lack of NFB (as well as its cathode biasing) have a big impact on its tone.