cartridge loading ?

If the phono pickup is open circuit, (disconnected from the preamp, or with a very, very high input resistor) it will produce voltage. Since the circuit is open no current will flow. Motion of the stylus is resisted only by its mechanical compliance.

If the phono pickup circuit is closed by a reasonable resistor value (say 47K) the voltage will cause current to flow. The current is dissipated in the resistor and that is power. This power is generated by the pickup, and power generation requires that work be done. In this case the work is the force that the stylus exerts against the electromagnetic force generated by the current flowing through the pickup coils in the pickup magnetic field. The stylus becomes less compliant. Thus, the loading resistor in the preamp affects the mechanical properties of the stylus, with obvious impact on sonic characteristics.

The pickup is a pretty wimpy generator and can't put out much current. When the resistor value is lowered, and more current is drawn, the pickup voltage will decline. When this happens the sound volume will decrease. This is from a purely electrical point of view. I suppose that the changes of stylus mechanical characteristics might counteract the electrical effects over some small range of resistor values. You can be sure that when the resistor value goes to zero, current will be maximized, but it will be very quiet.

Bombaywalla, thanks for the correction. I'll try to remember that a coil of wire moving in a magnetic field can't, sorry I mean "CANNOT put out any current whatsoever." Presumably, you learned your electronics from a better school than I. By the way, I recommend you avoid getting too close to any electric power generation equipment, just as a precaution.

Bombaywalla, Yes, The "magic" number is actually an RIAA derivative. It is a number generally used as an established "benchmark". It works not only at the line stage levels, but also commercial remastering from analog to digital format.

Based on remastering with the current commercial CD recorders in use, the actual recommended value is 300mv, as 300mv is what would be required to attain a 0db recording level with the recorder's level controls set at max. How RIAA actually arrived at that number? I can't tell you. But I would guess that SOME type of standard needed to be established.

The 325mv figure that I use, allows for a small working margin. Lord knows sometimes we need it.

Now if we could only find our original poster of this thread. I think he may be sitting back reading all of this and thinking, "Don't these guys have a life?"

Can you blame him? Ed.

Jameswei,

I stand corrected!
I realized this a bit after I hit the "submit" button. Writing too late @ night crosses wires inside the brain!

duh.
out w/ flu a few days but as i try to wade thru this, i fear i may have tried to return too soon.
i think my koetsu has an output of 0.6mv. i believe my melos phonostage offers 54 and 78 db of gain, i use the lower output since even that provides a higher level than my cd player. i am clueless about the capacitance of my various "phono" cables, altho i may have some documentation on the purist; they are all 1m. length.
i think i'm finally clear on the importance of the capacitance of the phono cable & preamp, altho i'm not yet clear on how to solve it, but i'm still struggling w/ the resistance/impedance issue: primarily i see now because of ignorance of fundamentals. i've got the electrons moving d/t the coil over magnet assembly. does increasing the value of a resistor to ground force more of those electrons to the tube grid? is this the formalism for increasing the load on the cartridge?
thanks,
jon