we've been selling this modification/upgrade for the ST70 for 22 years now!!
we are also now offering your choice of our classic hi-gain version with 12AT7 tubes,
or a lower gain version using 12AU7 (or even better 12BH7 tubes, which has
revised resistor values to optimize the circuit for these lower gain tubes
click here for our new BOOK store page
also some audiophile CDs, tubes, tools, connectors, and interconnects