My name is Rick and I am a newly proud owner (in waiting) of an ST 70.I wont have the new to me unit in my possesion until next week as it was just shipped yesterday.This will be my first tube amp! I bought it from a fella on another site and I think I made a good purchase.Currently I plan to play it through some KG4s I have here. I'd like to list the description of the mods made to it by the previous owner as described by him and would like some input from you guys with knowledge on this unit.Thanks in advance and I am looking forward to learning from all of the info available on this site!
This is a ST-70 that I purchased a few years ago and discarded everything but the cases and transformers. The chrome has some pitting and some of the lettering has rubbed off over the years. But on the insides the original circuit board has been replaced with a Triode Electronics board that gets rid of the 7199 tubes and replaces them with 12AX7's & 12AU7's. I upgraded this board with metal film resistors, Aura coupling caps, ceramic & gold plated tube sockets. The output tube sockets are also ceramic and gold plated. The Multi-cap is still there but only for show. It's function has been replaced by banks of Nichicon 450V capacitors with at least doubling the stock capacitance rating on each amplification stage to give a more focused soundstage and stronger bass than a stock unit. The input and speaker jacks are Cardis and are wired to the 8 ohm taps. The amp also has switches on top to switch between triode and pentode mode. The internal signal wiring is teflon cover silver. The driver tubes are Electro-Harmonix and the output tubes are matched set of Sevelanta EL-34's.