which gain setting for Bryston 4b cubed power amp using my RME ADI-2 DAC FS?

I tend to doubt the RME is fully balanced as they never mention it on their site as you think they would, and you’d also think if it was they would’ve included an AES/EBU input instead of just SPDIF and Toslink.  As the output of the balanced outs is higher than the RCA outs I’d think the 23dB gain setting might be preferable.  Call me crazy, but I just wouldn’t run a $7500 amp with a digital volume control in a $1300 DAC unless it’s just a stopgap for something better to come.  But that’s me.  Hope this helps somewhat. 

that was helpful, thanks

the RME is in fact a kind of stop gap

Use the one that sound better at the volume you listen.  My amp has gain settings as well and it depends on the preamp and your speakers.  

Yes I’m currently running my MSB Discrete DAC directly into my Benchmark AHB2 Amplifier. I have the amp gain at the mid setting of 17db and the DAC Output Impedance set to Low (150 ohms). This gives me a good volume range on my DAC. Volume control. Usually between 85 and 90 on a 0-106 scale. These settings also sound the best. I tried inserting the Benchmark HPA4 Preamp and found it to have benefit in SQ and I’m all Digital Streaming so no need for a variety of inputs. I did hear the MSB DAC with the Bryston 4b3 with the gain at 29db. It sounded fine. It’s always a delicate balance. In my case the higher 23db gain setting on the Benchmark sounded more forward with a loss of soundstage depth. 

listen to both.  not enough gain sounds dull and lacks dynamics.  too much gain sounds unrefned, slightly edgy, possibly too midrange forward and like turning up the volume will cause fatigue.  regardless of specs trying and listening to each gain  setting is recommended.