Instruct: Classify Amazon reviews into positive or negative sentiment
Query: Serious technical flaws in CD set

I wish I had taken the review by "A Customer" more seriously before ordering this 7-CD set of Shubert's Piano Sonatas performed by Wilhelm Kempff. Several of the CDs in the set I received have serious flaws both in sound quality and the technical recording itself. I have a good stereo system, not a boom box, and I bought the set from amazon.com not some Chinese knock-off. The pianist is fantastic; I am very disappointed in the technical production of this set. I am returning the set to amazon.com for a full refund.