Control volume with DAC or Preamp?

 Are you referring to the Benchmark DAC3 HGC? One volume control and lots of imputs/outputs. Eliminate your preamp. I think solves all your problems. Have one and love it. 

It appears the answers here are all over the place.  If it was me I would contact PS Audio to get an answer directly from the company.  

Connect the DAC directly to the amp and ditch the preamp if your system is purely digital. You should be able to achieve greater transparency because you removed the coloration from the additional interconnects, component, and power cord. 

Quite often the volume control in a preamp is better than one in a DAC. This is usually true if the DAC employs a digital control, since digital controls usually shut off bits to lower the volume, resulting in lower resolution as the volume is reduced. There are a few different techniques that DACs use in this regard, but generally speaking, you set the DAC all the way up and control volume with the preamp. This usually allows you more resolution than you can get by driving the amps directly with the DAC, since the DAC (in order to comply with Redbook specification) makes way too much output for most power amps to be driven past overload.

Thanks for all the advice.  I had been using the Benchmark LA4preamp at the highest volume and adjusting the listening  level with my PS Directstream DAC. As I mentioned, I heard a fluttering noise from the speakers while doing this.  I tried the reverse...DAC at full volume and adjusting the listening level on my Benchmark preamp.  The fluttering went away and the sound seems much clearer.   Both the dac and preamp volumes can be adjusted by remote control.