hello, I'm making my preamp, in the input stage I'm using a classic configuration called "instrumentation amplifier" as long as I use balanced inputs it's great but if I put the unbalanced input I'm forced to put in (-) to gnd. consequently the op amp (U2 in figure) goes to a gain lower than 1 and becomes unstable ... I tried to stabilize it by increasing RB and it works but I lose symmetry (especially if you reconnect the unbalanced input) and to be honest the sound coming out of the preamp is not the best in terms of correctness, above all the depth and the perceived quality of the medium-high frequencies are affected (for example the thump of the drum mixes with the sound of the cymbals). the configuration modified in red is much more current and functional. what do you think is there any other better possibilities to make the balanced and unbalanced connection consistent?
I apologize for my bad English
I apologize for my bad English
