I get an OPA2111 (KP - Dual LN DIFET, 8 DIP) sample and put them into my headphone amp GSP-Audio Solo DIP socket.
Before I had tuned them with an LME49720HA OPA (original are an AD823AN)
In my second headphone amp WNA MKII I use two
OPA627 now.
The OPA627 is an Precision High-Speed Difet® Operational Amplifier and have an slewrate from 55V/usec
The
OPA2111 is an Dual Low-Noise Difet® Operational Amplifier and have only an slewrate from 2V/usec
I wonder thats the OPA2111 sounds so good too,
despite its low slew rate.
It seemed to be the better choice that the modern high end LME49720HA
Modifications are my passion
In all the time I had done this, mostly I preferred FET input OPAs before BJT input OPAs.
TI offers other high fidelity JFET input audio dual op amps like OPA2134, OPA1642 and OPA1652, or bipolar input audio duals like OPA1602, OPA1612 and OPA1662.
What are your experience between OPA2111 and OPA2134 - the others from TI are only SOIC packages. Another way is to use an adapter - two 8 DIP to one.
To my ears the OPA2111KP sounds very bright and clean, almost harsh...The OPA2134 sounds warmer and less clear, almost fuzzy...