As you've probably gathered from reading our string descriptions, the selection of string can make a profound difference in response, so D'Addario offers strings in three flavors: Orchestra, Hybrid, and Pizzicato.
The Orchestra strings are specifically designed for - you guessed it - orchestra players. They are, of course, very bowable, and use a winding and material that creates less sustain. This is done on purpose, of course - orchestral players are not looking for the same level of sustain that a jazz pizzicato performer would want. However, they've still got great thump power and enough sustain for many players that play a variety of styles. They have less "presence" and sound somewhat "darker" than the Hybrid Helicores, and definitely more so than the Pizzicato Helicores.
The SOLO Strings are a version of the Orchestra Strings designed for solo repertoire; you tune each string up one whole step to F#-B-E-A for easier access to higher solo passages. D'Addario doesn't brand these as "Helicore Orchestra" strings, but they are very similar to the orchestral set and are generally used by orchestral players, hence the inclusion of the "Orchestral" designation. (They have purple silk with a gold spiral on the ball end).
An Extended E/C string (for low string extensions) and a Low B string are also available in 3/4 size.
We are sorry to hear of your experience. If you experience a problem with your strings (or string set), you may contact us (D'Addario) to see whether a manufacturing mishap is the cause. If you wish to return the string(s), visit http://www.daddario.com/ra. Please return the string or set in question in its original packaging (including corrosion intercept bag if possible). This will help us determine if a defect or other malfunction has occurred. Upon receipt and evaluation, if a manufacturing defect is revealed, we will quickly send you a replacement.
NOTE: Though it may not be the case in your situation, please keep in mind that premature string breakage is often caused by burrs or rough edges that develop at the nut or bridge/saddle. These rough edges are often difficult to see, but can be ruthless on strings. If your string continuously breaks at the nut or bridge, please check these points of contact for a nice, smooth surface. If burrs or rough edges are found, contact your local music shop or luthier to perform the necessary minor repair to resolve this common problem.