CS-300F is equipped with GE JAN-6197 which was developped for use in Computors and we used this tube for audio purpose for the first time in the world. We purchased this tube many years ago and have been seeking for the best circuit design to bring the best performance of this clean tube. For Driver circuit, we used a very high quality tube 17EW8(Hi-FI) specially produced for Hi-Fi use by a major Japanese electronic manufacturer.