What lives inside the feedback loop

A filter placed after a delay touches every repeat exactly once. The tail gets darker than the source, and it stays that darkness all the way down.

A filter placed inside the feedback path is a different arrangement. Every pass through the loop goes through it again. Six repeats through a low-pass is that low-pass applied six times, and the last repeat is not a little darker than the first — it is somewhere else entirely.

A 12 dB per octave high-pass and a 12 dB per octave low-pass, each sweepable across the full 20 Hz to 20 kHz range, and a soft-clipping saturation stage. All three sit inside the feedback path rather than after it.

So the repeats are carved again as they decay, and driven again as they decay. The tail does not just get quieter; it moves.

Because it is where they were on the machines this kind of effect is descended from. Tape lost high frequencies on every pass because the tape was in the loop. Bucket-brigade delays lost bandwidth the same way, for the same structural reason. The characteristic sound of those units is not a filter setting, it is a filter applied repeatedly.

The three character voicings are that same idea packaged: Digital keeps full bandwidth and stays transparent, Tape is warmer through the top with musical saturation, Analog is darker with stronger colouration. They are not equaliser presets sitting after the delay. They change what the loop does to the signal each time round.

Because the effect compounds with repeat count, a filter setting that sounds mild on the first repeat can be the dominant character by the sixth. The instinct to turn it further because "it is barely doing anything" is usually wrong, and the evidence arrives four repeats later.

The other thing to know is that filtering inside a loop also changes how much energy survives each pass. The same feedback number decays at very different rates depending on where the filters are set, so the two controls are not independent even though they look it. Narrow the band and the tail shortens without you touching feedback.