Cartridge Loading.....Part II

Dear @intactaudio  : You are rigth and what PM IAR 5 posted was confirmed by J.Carr when in other thread on the same issue posted:

" To claim that the loading affects the measurable frequency response of the cartridge is bogus. However, if inappropriate loading bathes the phono stage in copius amounts of high-frequency noise, it may start to distort (unless the designer implemented various techniques to make sure that this won't happen), and the result will likely be intermodulation distortion.  "

Regards and enjoy the MUSIC NOT DISTORTIONS,

R.

The lower value 200 ohm vs. 47k ohms means more loading which tends to attenuate higher frequencies (because we hear things in terms of overall balance, attenuating highs can also  be perceived as more bass).

If light loading is entirely added intermodulated distortion and the "real" and "accurate" sound is what you get with high loading, I will take distortion. 

The loading has no effect on the cartridge other than making the cantilever harder to move. You can take any LOMC cartridge and put it on the bench. Using a squarewave generator (at a very low loutput, so as to not damage the cartridge), you can put the cartridge in series with the squarewave and then measure the output. With no resistor in parallel this is an unloaded inductor. What you will see on the oscilloscope is a nice squarewave, looking really quite a lot like the input, neither attenuated or rounded and with no overshoot! This is simply because the inductance of the coil is too tiny to ring at audio frequencies.

So the 'brightness' we often hear is coming from somewhere else!

Putting a resistor in parallel will not affect that. So the resistor is not affecting the bandwidth of the cartridge. But it is interacting directly with the electrical resonance, which is a product of the inductance of the cartridge and the capacitance of the tonearm cable.

As we can see from the page http://www.hagtech.com/loading.html

the peak can be substantial. The reason is something called 'Quality' or simply 'Q'. Inductive coils can be long and narrow, having a low Q value, or short and wide, having a much higher Q value. The higher the Q value the higher the peak and the narrower the band of frequencies it covers. LOMC cartridge have high Q coils in them for lowest mass.

Some preamps don't like having all that RF noise caused by the peak at their input. So they do weird things and one of them is distortion. Loading knocks out the electrical resonance and if the preamp has a problem with the RFI, the brightness along with it.

One would have to compensate for the loss of gain from using such a resistor, but, one will hear quite a difference in sound

This statement is only true if the preamp is sensitive to the RFI at its input. If not, no difference will be heard. Most designers simply don't take the implications of this electrical resonance into account in their phono designs, which is why this loading conversation persists.

Sort of makes a good argument for transimpedance as the initial stage of a phono preamp . . .

Ralph

The loading has no effect on the cartridge other than making the cantilever harder to move.

Isn't that essentially suggesting that compliance has no effect on the sound of a cartridge?

did you ever get a chance to look at the copy of IAR #5 I sent you?  I find it entirely plausible that making the cantilever easier / harder to move would have a sonic impact on the sound of a cartridge.  Add to this that this effect will be dynamic based on the musical content and things get interesting.  If you trust the measurements made by Moncrief, he clearly shows a reduction of IMD and it isn't a huge leap of faith to believe that the degree of measured IMD change he shows would have an audible result.

dave

@rauliruegas

What Jcarr and in parallel Ralph are saying is completely different than what is presented by moncrief.  They all agree that loading has no effect on the measured frequency response of a cartridge but any similarities end there.  Ralph and Jcarr suggest the unloaded "harshness" is caused by the MC cartridge inductance resonating with cable/input capacitance resulting in input overload of a phono stage that is not "RFI stable".  Moncrief suggests (and shows) that for MC carts, IMD distortion levels are directly related to applied cartridge load.

dave