I/V rolling (Stock LPF: LM4562)
LM49720 Stock– well balanced, clean, airy and open but slightly to the warm side.
LM49720 'Metal Can'– almost identical to stock, but just a tap fuller in body.
OPA2604 – denser, not as airy and open as stock.
OPA2209 – bass note is a little lean, good height.
OP270 – Also dense, but a little better soundstage than OPA2604.
OP275 – Leaner and brighter than stock, almost grainy. Good soundstage.
AD8066 – Even brighter than OP275, but without the graininess. Slightly flat in soundstage but good width.
OPA2227 – Forward, full and bright, slightly grainy.
OPA2134 – More mid centric, lack soundstage.
MUSES01 – Similar to Stock, with better dynamic and impressive soundstage.
MUSES920 – full and forward, like smoother OPA2227.
LPF rolling ( Stock I/V: LM49720)
LM4562 – stock, again: well balanced, clean, airy and open but slightly to the warm side.
LM49720 'Metal Can' – Similar to stock, slightly less dense and more open in the mid.
OPA2604 – thick and slow, grainy.
OPA2209 – Full, similar to OPA2604 but without being overly thick and slow.
OP270 – Lean, slightly lacking in bass, slightly bright.
OP275 – Well balanced, though soundstage isn't great.
AD8066 – Very airy and open, great soundstage but a little bright.
AD8620 – Like a tuned down version of AD8066, with better body and smoother presentation.
OPA2227 – warm and slightly dull, but sparkly on the top.
OPA2134 – similar to OPA2227, more mid centric and not as sparkly.
MUSES01 – Similar to stock, but slightly better dynamic and soundstage.
MUSES8920 – somewhere between OPA2227 and OPA2134.
Thanks to ClieOS for detailed combination testing
on Head‐Fi review: