All compressors with kill the high end to some degree or another. The LA2A is no different. How much and at what freqs are affected depends on all the things related to using compression. The program material going into the compressor, the compressor attack, release, threshold, ratio and the gain reduction it does. On the LA2A you only get manual control for level (which controls both level and threshold) and for gain reduction which is pretty much ratio but is related to the level control as well as attack and release which are fixed, but vary in settings dependant on the input level and program material content.

The LA2a was a broacast leveling amplifier.. It does roll off the highs a bit if you hit it real hard and there should be a swithc that puts it into a mode that compresses the high frequencies more.

I would ask the guys at tech talk forum. There is a lot of people that build that thing.

Thanks for info, You folks confirmed my suspitions about the design causing the roll off. I have designed and built a number of types of equipment but never tried to build a compressor before until a friend asked me to build one for him for his recording studio.