cartridge loading ?

Bombaywalla, Thanks, I was hoping SOMEONE else would help out with this. My approach does get a little hairy, BUT it is very thorough. With the correct calculations, the numbers don't lie.

Also, I found after locating the specs on the Koetsu Onyx, that the output is actually 0.2mv @ 1khz/5/cms, vs. 0.4mv as you stated with an output impedance of 5 ohms, and a recommended loading of 5-100k ohms.

A 64 db gain would be optimum for a 0.2mv output. This calculation is based on achieving a 325m V rms output @ 5 cm/s.

I offer this info not in the spirit of disagreement, but in the spirit of clarification.

Now let's just hope that Jon is not so disgusted that he went out and purchased a CD player. :>)

Thanks again for your contribution Bombaywalla, Ed.

Jameswei,

Don't know where you learnt your electronics but a phono cartridge is a PASSIVE device. It has nothing in it but a wound coil of wire & some magnets. It CANNOT put out any current whatsoever even if it tried to! All it can put out is a VOLTAGE. As already stated by Herman, the VOLTAGE put out by the cartridge is FIXED! Nothing under the Sun can make it increase (it can decrease as the cart. ages & the magnets decrease in their strength but this would happen over several yrs, maybe 10s of yrs).
If the volume is increasing by decreasing the resistance @ the phono pre, I suspect that the resistance (in the input stage of the phono pre) is part of an electronic ckt. that is sets the voltage gain of that ckt. Decreasing it could increase the gain of that ckt. Hence the volume increase. If I have wrongly assumed this & the resistance you are talking about is the resistance you add/take-away externally, then there should be NO change in volume i.e. It doesn't make any sense that the volume changes w/ change in ext. resistance.
Hope that this clarifies.

Buscis2: Cool! I accept you output voltage numbers of the Koetsu. I only GUESSED at the output level as I have no pesonal experience w/ this part. cartridge. I would suspect that 60dB total gain would be sufficient but if your experience shows 64dB is better, then, so be it. I suppose that achieving 325mVrms @ the phono pre is a "magic" number to get max. gain from the pre onwards (to the speakers)?? i.e. it is the max. input to the line-stage of the preamp?

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.