Anyone ever had a TK 421 modification done?

Category: Amplifiers

Who did the work and was it worth the investment? Considering this for my Idyot Uberganev series mono blocs which already put out rather hefty power. Looking for that SET sound quality at over 250 WPC! For what it's worth my source is a Garand M1 (fantastic accuracy) into Mamalashon bipolar speakers. No digital in this system- strictly analog. thanks in advance!