THE FIRST all-digital budget series, Pro Arte Sinfonia, is on the market. Produced by Pro Arte, which also puts out the Quintessence budget label, the new series retails go for as little as $5.95 a disc or cassette (a bit less multidisc sets).

That is about one-third of what some audiophile labels cost, but no production corners appear to have been cut. The discs are pressed by two of the country's finest plants--Wakefield and KM--and the cassettes are on chromium dioxide tape. The Sinfonia line also is to be available on the new compact digital discs from Japan in the fall.

It must be acknowledged that there are no big-name performers on the Sinfonia releases, at least so far. The one recognizable name in the first batch, in fact, is that of Herbert Kegel, the East German conductor we've known almost exclusively from his recordings of choral works. On Sinfonia he conducts the Dresden Philharmonic (not the famous Staatskapelle) in sound and sturdy performances of Beethoven's Fifth and Seventh symphonies that, if they shed no new light on these familiar works, leave very little to be desired and benefit from fine sound.

The big surprise, though, is Sinfonia's two-disc set of Bach's four suites for orchestra, performed by the New Bach Collegium under Max Pommer (SDS-700; cassettes SCS-700). I had never heard of Max Pommer, but a half-dozen hearings have convinced me that this set belongs at the very top of the list of available recordings of these much-recorded works.

The New Bach Collegium, which adopted that name only four years ago, is a 20-year-old chamber orchestra drawn from the ranks of the Leipzig Gewandhaus Orchestra. Pommer, to judge from his elaborate annotation as well as the performances themselves, not only understands this music down to the ground, but feels the purpose of combining performance with scholarship is to bring music to life on its own terms. These are exceptionally gutsy, vital performances, as well as exceptionally stylish ones, and without a hint of self-consciousness in either respect.

The ensemble is not an "original instruments" group, but a collection of alert and expert players who not only reflect, but apparently share in full, Pommer's enthusiasm and affection for this music, as well as his understanding of the style. I'm sure Karl-Heinz Passin, the soloist in the Second Suite, is not playing a wooden flute, but both the sound and the spirit are just what one wants here.

These suites are not chamber music, and not particularly intimate in character; they represent Bach in his most extroverted vein, and that is how they come across in these joyous performances. There is nothing discreet or timid, for example, in the prominence given the drums in the Third and Fourth Suites. Pommer doesn't treat their part as simply a continuous function, but encourages them to exult with the brilliant trumpets in all their festive glory.

The much-abused Air in Suite No. 3, given a funeral parlor connotation in so many slowed-down and inflated treatments (yes, even in some of the supposedly "authentic" performances), reasserts its own character and dignity here in an all but seamless flow at a convincingly natural pace. The appoggiaturas in the ensuing Gavotte are both smooth and sassy: if you're going to attempt them at all, this is surely the way.

The interplay of winds and strings in the First Suite as heard here is likely to stun more than a few listeners into belated recognition of what an accomplished colorist old Bach was, after all. Dozens of delightful examples might be cited, for throughout the four sides the playing itself is on the highest level and the approach is enlivening in the best sense. The sound is rich, full and well balanced, the pressings exemplary. I don't think there is, or has been, so thoroughly satisfying a set of these suites on records at any price.