Athearn Genesis F7 Question

Hello, I am looking for some info on Athearn Genesis F7’s and the Brightness of their Headlights with Sound and DCC vs Non Sound. My sound equipped Genesis F7 appears to have very dimly lit bulbs. On my non sound straight DC and then converted with a TSC decoder with 1,5 volt regulator, the bulbs appear much brighter. Has any one had this same problem? Any ideas?

Thanks

George