On Tue, 2004-05-04 at 13:41, Aaron Heller wrote: > There are further considerations beyond RIAA equalization and gain. > > Moving magnet phonograph cartridges are designed to work into a specific load, typically 47k ohms and 250 pF (e.g., see "Recommended Load" for a Shure V15 on http://www.shure.com/v15vxmr.html), which is significantly different than the load presented by a microphone preamp. The wrong load will change the frequency and transient response of the cartridge. > > Phono preamps are designed to present the correct load to a phono cartridge. Good ones have switchable loads to accommodate different cartridges and to compensate for the capacitance in the connecting cable. In high-end gear, it is common practice is to modify the input circuitry of the preamp to specifically match the cartridge and cable in use. > > There are also moving coil phono cartridges, which have different requirements. > > By contrast, professional microphones typically have source impedance of about 150 to 200 ohms and are designed to be loaded with a pure resistance in the range of 1 to 5 k ohms. (here are the specs for a Neumann U87 http://www.neumann.com/infopool/mics/en/u87ai_t_data.htm). > > If you are serious, my recommendation would be to use a dedicated phono preamp. There are some very good ones for around $150 like the Parasound PPH-100, which handles both MM and MC cartridges. > Why would I want to spend $150 on a preamp? I get almost exactly the same sound from the mic preamps and JAMin EQ that I get from my stereo amp (with built in phono preamp). After I record it I'm going to encode it in ogg vorbis. I seriously doubt that I would be able to hear the difference between the $150 phono preamp and the combination mic/line preamp and JAMin. Jan
