THS4522: THD+N vs Gain

Morning Hao, 

That is a deceptively simple question with many layers to the reply.  

1. 1st, the THS4521 and THS4522 were upgraded to the THS4551 and the THS4552 

a. improved noise,particularly better 1/f and lower popcorn noise

b. improved distortion 

c. much better DC and drift, which you do not care about in audio

The question about gain is an interesting one but gets into many layers of of LG phase margin. I covered a specific case of this in this article starting for an FDA in Figure 6. 

https://www.planetanalog.com/are-inverting-attenuators-with-voltage-feedback-op-amps-inherently-unstable-and-why-might-you-want-to-apply-them-insight-11/

For better answers, include either your schematic as a TINA file and/or your requirements. 

Also, there is a 3 part series on applying the THS4551 to an audio application just starting with the Feb.2020  issue of AudioXpress magazine, a subscription mag so I cannot include those links/files.