Bulgaria's Sofia Philharmonic Orchestra came to the Kennedy Center last night and sounded like a likable, if rough, ensemble. What was not at all rough about the event was 31-year-old virtuoso violinist Mincho Minchev's playing.

He performed the Paganini fifth concerto, one of those finger-busting pieces the great violinist wrote to display himself. Like the others, it must have twice the notes of the Beethoven concerto, though half as long. In between all those double stops, cascading scales and (can you believe it?) double trills, Paganini didn't stuff a great deal of musical thought. But, played in style, it's fun as it can be.

Minchev tossed it off like a breeze. He has the effortlessness it needs. Lots of young musical thoroughbreds can handle all the notes, but they are rigid and stiff. You should have heard the lustiness with which he launched into the "alla campanella" finale. We'll have to hear the purity with which he handles Bach counterpoint another time.

Each member of the orchestra is a graduate of the Bulgarian State Conservatory. The conductor last night, Konstantin Iliev, has been with them since 1956. The only real test of their mettle was the Dvorak eighth symphony. What was most appealing was how relaxed they sounded. Particularly in the first two movements, they switched gears instantly with Dvorak's moods.

But the solo virtuosity this work requires from the orchestra, particularly in the winds, just wasn't there much of the time. And balances were off just enough to rob this soaring symphony of its pristine delicacy.