cartridge loading ?

Jon, you need to help complete the equation. I would have to assume that you are using a phono pre that has adjustable input impedance. Are we talking moving magnet or moving coil?

Phono cartridges have circuits which consist of coils of wire. These coils have electrical resistance and inductance parameters which make them sensitive to resistive and capactive loading created by the tonearm wiring, interconnects and circuitry of your phono pre. Cartridge manufacturers will generally specify the proper load resistance capacitance with your particular cartridge.

The cartridge will obviously present the flatest frequency response curve when the manufacturers load is observed. Improperly loaded cartridges will in fact exhibit frequency response dips and peaks like you describe along with emphasized surface noise.

To complete this equation thoroughly you really should consider the following factors;

The capacitance per foot of your interconnects,
The capacitance of the internal tonearm wiring,
The load components inside your phono pre.

Often this information is specified but you may find that it is not optimum for your cartridge. Many designers put way too much capacitance in their preamps disregarding (it would seem) that the tonearm wiring contributes to this amount.


A couple of general rules of thumb. With moving magnet, the higher the capacitance, the higher the degree of (as you put it) "muffling" of the sound. As an example, a moving coil cartridge should be hooked into a phono pre set at an impedance level approx. 2.5 times the impedance level of the coils of the cartridge. The impedance of the input of a step up transformer should be the same or slightly higher than the values of the coils of the cartridge.

Does this help or did I just confuse matters worse?

the cartridge is a koetsu onyx. i've rewired my tonearm w/ cardas 33 ga Cu. i'm experimenting w/ phono interconnect using the sound of guitars i know or own as reference. currently i'm closest w/ modern audio design "pearl" altho i'm still switching between the mad, some purist audio design phono cable & some homemade cable w/ extruded 5 9s silver & eichman plugs. the phonostage is a retubed mar modded melos ps 1 gold.
altho i've read that koetsu' are supposed to run into 100 ohm loads, i seem to prefer a 390 ohm load i have avail. since there is no " factory" documentation on koetsus and there are varying opinions on the net, how do you determine 2.5x the impedance level of the coils?
i'm also confused about impedance. it looks to me as if my controls select resistors of increasing value and i've encountered threads that refer to " resistive" loading and i've assumed that i was selecting an "obstruction" to the flow of current. does a resistor generate a frequency specific "impedance" because the coils oscillate around a null point? is that all it takes to move from resistance to impedance?
as i look at this it occurs to me that perhaps i need a primer in electricity. is there a concise reference i should know before sending out threads like this?
thanks for your patience'
jon

Jon, Love your analog, Huh? I love ya like a brother already.

I am going to attempt to address your response paragraph by paragraph, but I really hope that some of our Audiogon brothers/sisters pipe in and help us out.

First: Do you know the capacitance/ft. of the Cardas 33 ga. tonearm cable?

Second: I'm sure that you realize that the capacitance/ft specs are probably all over the place between the five 9 silver, the M.A.D., and Purist Audio cable. What have you finally settled on using, and what is the capacitance/ft?

Third: You are probably preferring a 390 ohm load on your 100 ohm preferred Koetsu because of the capacitance of your wiring (whatever that capacitance may be?)

Fourth: I am sure that one way or another, SOMEONE professionally representing Koetsu could provide you with the coil impedance levels. Personally? I would pissed if they couldn't.

Sixth: Quite honestly? I can't tell you what load components are used in your pre, or what values they are, as I am not familiar with the unit. HELP on this one fellow Audiogoners!

Seventh: (And I'm not sure on this one) In theory, a resistor/array could generate a frequency specific impedance, but I don't know circuit design thoroughly enough to provide you with a specific configuration. HELP on this one too fellow Audiogoners!

Eighth: Back in my days of E/M design/packaging we used to have what was considered the "Electronics Bible" that was somewhat similar to the "Machinery's Handbook" or the "Mark's Standard Handbook For Mechanical Engineers". I still own both of the aforementioned, but the "Electronics Bible" escapes me (Too many drugs). Audiogoners. HELP! Audiogoners.

Last, There are some very intellegent (and some not so intellegent) contributors to this site who I'm sure can help us out here. Hopefully some will pipe in and contribute to this thread.

This much I can do: If you were to provide me with the following info, I could perform some calculations and give you some hard numbers to work with.

Give me your cartridge output, I could calculate the optimum gain of your phono stage.

Give me the phono stage sensitivity specification, and I can calculate the db gain of your pre.

If we know the gain and the maximum output, we can then calculate the maximum input overload. We will then calculate the maximum cartridge output that the pre can properly amplify without distortion.

Oh, for the love of music......Ed.

The cartridge acts like a curent generator i.e. it trys to put out the same current no matter what the load is.

Using the equation V = I x R (voltage = current times resistance) it is clear that as resistance goes up with a constant current, the voltage will go up. The phono stage amplifys this voltage so the bigger the load resistance, the higher the output.

I'm not sure what you mean by attack distortion, but as a general rule, the high frequency energy will increase as the load resistance is increased.