# Question about cartridges and pre amp

I do not understand how you match up a cart. with the gain of your phono amp. This is from the Musical Fidelity web page about the amp. I have.

Signal / noise reference
for 1Volt RMS output > 94dB Moving Magnet,
('A'-weighted, at half volume).

Input sensitivity for 1 Volt RMS output > 83dB Moving Coil,
('A'- weighted, at half volume).

Input impedance 2.5mV Moving Magnet.
350µV Moving Coil.

Overload margin 47k Ohms
31dB

What are the lowest voltage outputs than can be used with this phono amp. MM and MC

Thanks

Tim
flemke
1 response
 12-12-2003 8:08pmI'm not the best tutor on this subject, but since there have been no responses to you I'll start the ball rolling and maybe others will add to / clarify my comments.First, a word about the use of "db" as a measurement: the decibel is not an actual measure of output. Decibels refer to the relative level of one signal in relation to another, and the decibel scale is logarithmic (base 10). For example, a 60db increase in amplification means that the amplified signal is 1 million times stronger than the original input signal; etc. Decibel level is also used to describe the relationship of the distortion in a signal to the signal itself: a CD's distortion level is typically about 96-98db lower than than the music signal. What is more relevant to discussing the loading and gain factors for a given cartridge and phono preamp are:1. the output voltage of the cartridge (MC's typically have output voltage in the range of 0.2 to 0.5 mV, although some high output MC's have voltages as high as 2.5 mV. MM's typically have output voltages from 3.0 mv up to 6 mV, or higher.)2. the impedance, or loading, in ohms (MM's usually have an impedance of 47k ohms, whereas MC's are typically much lower, say around 100 ohms. The third kind of cartridge, the moving iron models made by Grado, usually have electrical characteristics similar to MM's.)As a rough generalization, you will want to pair a MC cartridge (except the very high output types) with a phono preamp that has at least 60db of gain. For extremely low output MC, you may also need to have a transformer or additional gain stage BEFORE the phono preamp (the so-called head unit). High output MC's can be used with phono preamps normally suited for MM's and having gain in the 40-45db range.You will also need to set the impedance of the phono preamp to match that of the cartridge to ensure flat frequency response.MM cartridges are generally quite happy with phono preamps that have 35-40db of gain. The impedance should usually be set to 47k ohms, also to ensure flat frequency response.If you want to get into greater detail and technicalities on this subject, I recommend you buy Robert Harley's book on high-end audio and home theater, which can be purchased online from either Amazon.com or The Audio Advisor.