Keep the SP3! It is a TRUE classic and worth some restoration! But don't send it to Audio Research - they will charge way too much! Even in its present state it can compete with today's top preamps! Just changing the power supply caps and adding a set of NOS tubes will be worthwhile! I own an SP6 (1976) - and speak from experience!
Nuprime vs preamp rebuild.
Had previously queried community re value of upgrading dac. In brief I have an AR SP-3 preamp, Prima Luna HP amp, Magnepan 1.7 speakers. The dac is from HRT and is (I believe) their original model. Good quality interconnects and power cord. Up to this point, have been using Spotify Premium as streaming source. One respondent recommended getting the SP-3 up to speed. Last service is long ago, though usage has been light. The price of a rebuild done by AR is about 3K, all costs considered. Another respondent advised purchasing a Nuprime 10 which would cover both the preamp and dac issues. Would very much appreciate any thoughts re these options. Thanks