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?

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.

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.

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.

Hi Jon, I had that nasty flu a couple of weeks back. I'm STILL feeling the residual effects. Hope you're feeling better.

I'm confused. I looked up the Koetsu Onyx on the Elusive Disc website. It states that it has an output of 0.2mv. Is this cartridge offered with an "optional" ouput of 0.6mv also? Is the information I am being provided incorrect?

The difference between those two figures is somewhat significant. A 0.2mv output would require an optimum gain of 64db vs. 55db gain with an output of 0.6mv.

If your Melos is providing you with either 54 or 78 db of gain, you could now understand why you are using the lower output setting. A 0.6mv cartridge output would work almost perfectly with your 54db phono gain stage setting as (by the numbers) it would actually require 55db. You are really not going to get any closer than that. BUT, if it is in fact a 0.2mv output, it would also explain why you are experiencing the sound characteristics you described in your original post.

I think now you can see why I use my little calculations/formulae. THEY WORK! It helps to take all of the guess work out of these equations. They allow you to make a more accurate selection of cartridge/phono pre right from the very start or, in the very least, give you a closer approximation of where you need to be. (Measure twice, Cut once)

If you could, recheck your cartridge output. After that has been firmly established, we can then address the capacitance/operation issues.

Jon Re; Onyx cartridge output. That would explain it.

And No. The suspension of your cartridge would be unaffected by load and is not considered adverse.

And, it's been a pleasure, Ed.

Happy Listening.