EE MiniMax Dac Tube Rolling?

Has anyone ever put a 12AX7 tube in their stock EE MiniMax DACs? I was loaned one yesterday, gave it a quick listen and when I put in a NOS GE 6189 tube or a RCA Grey plate old stock tube the sound from the EE MiniMax as so so. It was like blankets were thrown over my headphones. I would switch to the solid state dac and the music would sound fine. The tubes I used worked perfectly well in other tube preamps I had so I don't know if I just need a higher gain tube.

I don't have any 12AT7 tubes laying around so I can't try those.

Thanks in advance.