I ran into the same problem. I have a bam200 and a trace Elliot elf. Both very similar but the elf doesn't do this and neither does my carvin mach 100.
After much debating I decided to chalk it up to the Mosfet preamp compressing early on even though the signal is not clipping on the input indicator.
My only work around is to keep the gain very low and crank the master volume to desired level. This may not give you the volume and headroom you want but it's worth a try.
I now use it as a small living room amp that I run my zoom g6 through and use either the elf or the mach 100.