cartridge loading ?

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.

Jwblaschke,

Since u r using a Koetsu, are you also using a step-up xformer either ext. or built-in? If I had to guess, I'd say you are. If the Koetsu is 0.4mV output, then you need 60dB TOTAL of gain in your phono section i.e. phono pre & step-up. This 60dB number is valid down to 0.15mV output.

The resistor loading provided to the cart. is a resistor to GROUND! Thus it is not in the signal path & thus does NOT divert any music signal into itself. That is why there is no attenuation of the music as you keep going higher (to 1K Ohm).

Intuitively, the coils in the cart. form an inductor. This inductor also has a DC resistance. It has to 'cuz it is (very fine) coiled wire, which, by Phyiscs, will DC resistance. This DC resistance is usually stated by the manuf. - 13 Ohms or something like that. You do not want to load down the music signal as it comes off the cart into the phono pre hence Buscis2 suggested an impedance 2.5X. I have found that 10X is usually much better. Thus a 100 Ohms phono pre input is OK for a cart. DC resistance of 10 Ohms IFFFFFF you are *not* using an MC step-up. I'll come back to this later.
Further, the capacitance of the interconnect + that of the phono pre creates a cap to ground. Now, you have a low-pass filter where the -3dB corner is set by the phono pre load resistor that is in parallel with the cap. By selecting the correct value load resistor you can shape this low-pass filter's freq. response to suit your listening preferences. In general, too large a load resistor creates an amplitude peak just before the filter rolls off & this creates an emphasis on the high freq. Some prefer this & it *appears* that you are one such person. That's just fine - chose a load to suit your preferences. OTOH, too low a value cause in-band attenuation & the sound becomes 'lifeless', 'dull', 'no sparkle', zero dynamics', etc.

If you are using a step-up, then observe what ratio you are using in the step-up. Say, that it is a 1:5 step-up. Thus the impedance is xformed by 5-square, i.e. 25, to the side of the cart. Usually, the way to use a step-up is to RETAIN the 47K default load in the phono pre & add, IN PARALLEL, some resistance (to ground again) so that the cart. "sees", the correct impedance. Manuf. suggested imp. is a good starting pt. & you can fine tune from there.

Supposing you retain the 47K default imp. & use NO add'l resistance, then the cart. sees 47K/25 Ohms. I don't have a calculator handy so do work out the Math. If you add another 47K in parallel (either solder it on or use the provided load binding posts), then the net imp. will be 47K in parallel with 47K, which is 47K/2. Then, this is xformed to the cart. side as (47K/2)/25. This is the final imp. the cartridge sees.

In general, the amt. of cap. in your interconnect plays a vital role in the sonics as it part of that filter. The biggest contributor to the total cap. should be the phono pre input stage only. That is why you see many people having very short interconnects from cart. to pre &/or step-up to pre.

Usually people do not approach this issue as stated by Buscis2 in his 2nd post as it gets hairy very quickly! Just ensure that your interconnects are not of the high cap type & that they are only as long as needed.

Long post, I know. Hope that it helps you. FWIW. IMHO. YMMV.

Let me get this straight. When you decrease the resistance at the phono preamp, the volume should go up? That's what I observe with my setup. This is called "loading" the cartridge. When the resistance is lowered, the cartridge is required to put out more current to drive the phono preamp (just like a low impedance speaker is a more difficult load to an amp). The burden, or load, is GREATER when the resistance is lower. If the cartridge is able to do this, the volume should go up. Eventually, the cartridge runs out of power and the sound deteriorates. Is this what you observed?

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.