The Definitive Series Gold Pin ECC82 Trio's are Handpicked, Curve traced, Matched and supplied with a graph showing the curves of all triodes being matched throughout their operating range at full working voltages. The obvious application for Definitive Series tubes is any tube preamp, compressor, or processor and of course any stereo application. You can of course use these tubes in guitar amps if you simply want the best of the best!