Hey Tommi,
yes, Roll is attenuation working like a smooth low or high cut. See this site for diagrams and manual of the unit:
http://www.preservationsound.com/?tag=fairchild
If you´re quick with the soldering iron, you might build this unit in 2-3 hours, the kit is giving you the components in such a thought trough manner.
I build several units, where I changed transformers and could achieve a hughe improvement in sound.
In some LA2A Builds, I used Sowter and then swapped for old UTCs.
In a Sta Level Build, I used old Collins (in) and Edcors (out), then swapped them for Sowters.
In a TG1 Build, I swapped Carnhill Inputs for some Irons pulled from some BBC Broadcast console.
All of the changes affected the sound of the unit, especially in frequencies in the high and low end. Most of the times I found this to improve the sound, but it´s a matter of taste after all. Some people discuss the benefits of different brands of transformers at length somewhere round here, so you may dive in if you interested.
I will report back as soon as my Sowters arrive for this unit and I can give first hand information about wether it sounds "better". Might post some Sound Files.
