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In Reply to: Phono preamp with MC loadings below 100 Ohms? posted by tketcham on September 8, 2006 at 09:05:04:
Both terms are mostly interchangable however the former is typically associated with transformers, the later with an active devices. Pre-preamp dates from the days when "preamp" implied what we'd these days probably call a "full-function" preaamp, or equivalently, a line-stage (preamp) with built-in phono stage. Finally since very many of such preamps supported only hi-output MM cartridges something was needed before them, i.e. "pre", to allow use of a MC cartridge ... hence pre-preamp.In either case one could think of the basic idea being to be a bridge between a low-output MC cartridge and a (standard) MM phono stage. Hence the voltage level is raised (e.g. from well under 1mv to the 2.5-5mv range) and the output of the step-up/pre-preamp should mate well with the 47k expected in a MM phono stage. The important point is that RIAA equilization IS NOT performed by the step-up/pre-preamp, all frequencies are raised by the same amount ... RIAA equilization will occur in the MM phono stage.
In either case as the device mated directly with the MC cartridge it must deal with cartridge impedance matching. In the case of a pre-pre a set of (switchable) impedance options would be typical (e.g. 30ohm, 100, 1000, ...) and for a transformer alternative (primary) winding may be available (by switches or multiple sets of inputs).
A phono stage that directly support MC might be said to combine internally a MC pre-pre (or transformer) with a MM stage ... at least conceptually that's not a bad way to think of it even if not technically correct (for a given device).
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Follow Ups
- Step-up and pre-preamp ... - bjh 09:43:39 09/08/06 (2)
- Re: Step-up and pre-preamp ... - tketcham 10:23:27 09/08/06 (1)
- Re: Step-up and pre-preamp ... - bjh 10:32:28 09/08/06 (1)