Thursday, November 20, 2008
All 7-pin Tube Based Phonostage
This began as a simple project to build a cheap phono stage for a very old turntable with a cheap cartridge out of parts on hand. However, it turned into a pretty good project that definitely outclasses the rest of my analog setup. Oh well, at least it was pretty cheap to build.
The filter is a pretty standard split RIAA filter. Calculations were done on Jim Hagerman's handy calculator (don't forget to account for rp!). The plate load constant current sources (CCSes) are from a DIYAudio group buy from a few years back. The circuit is in Morgan Jones and is the same circuit Bottlehead uses in their C4S kit -- you can find more about the circuit, and CCS use in general, elsewhere on this site. The CCS in the cathode is just an IXYS 10M45. The raw power supply is a CLC filter, and is pretty well isolated from the circuit by the CCSes.