Attention: Roland Cube combo owners

[DDD]

Hi guys,
I have Roland Cube-60 combo and use it for adjusting tone of my DIY stompboxes.
It has a very impressive JC Clean channel that I do prefer as a "clean amp".
But, sometimes, my friends ask me to match tone of their guitar gadgets with their amps, mainly Marshalls.
My Cube-60 has a simulation of Marshall JMP1987 (Classick Stack channel) and, theoretically, I can use it for that purpose.
At the same time this simulation seems not to be close enough to Marshall, and sounds pretty much darkly, bassy and dirty in spite of all my attempts to use it as a "clean Marshall".
Is this a widely spread situation or my personal problem?
How should I improve this to get "clean Marshall" from Roland Cube combo?

[Rob Strand]

Most solid state amps have a frequency shaping in the power-amp stage.  It generally affects the high frequencies maybe that doesn't match a Marshall frequency response.  You might be able to tweak that to push it closer to a Marshall.  Another big factor is the speaker.