Cartridge loading explained

[stpa]

Thinker,

You forgot the DC series resistance, 630 Ohms. With a 125 pf cable, 68 kOhms of impedance renders the best curve in my simulator.

[ben556473]

Hello, very interesting reading, I must agree with Bouquet about the shielding on cables I too have found this detracts from the realism of sound. If my phonostage has a stated 100ohm and 220pf loading for both MM and Mc inputs if I change the capacitors in the phonostage will this value change (as the better components will, I imagine, have a lower inductance) or is this value 'set' by the circuit design? Thanks for your help and understanding, Ben.

[ben556473]

Also BenC you can purchase Allen Bradley resistors from http://www.hificollective.co.uk along with some other types. Cheers, Ben Anderson.

[Reticuli]

So far I've found the Art DJ Phono Pre II on the budget end that gives these options (100pF & 200pF). Then there's the Pro-Ject Phono Box II SE, the Tube version, and then the Jolida A9. Or you can get something like the TCC-750 if you want 220pF or the original Pro-Ject Phono Box for 100pF if you don't want it switchable.

And I don't quite understand how a 125pF from headshell to cable end on the Technics 1200 means that particular cartridge would be optimal for it. It depends on the cart. Put the cartridge's inductance in that worksheet on the left, the 125pF plus the phono's own loading (e.g. 125+220=345) in the middle spot, and hit the button. It will tell you where the peak is and then scroll down to find out how far off from the 47k ohms you are. Try a different value for the phono's loading (50,100,120,220,340,440, etc) and see if you can get closer to 47k ohms.

Right? Tell me if I'm wrong.

Also, as far as I can tell the only cartridges that seem to need something other than 47k ohms are the ones with inductances of 50 mH, like the Grado Prestige. On those, you'd be better off with like 100pF and 10k ohms on the phono pre end, correct? But then I'm wondering if Grado really voiced all their carts just with their own preamp. I would assume they didn't do anything like what we're talking about.

[andyr]

Even then there are some variations, like semi-balanced (two inner wires and shield, connecting the shield on one side), but these are more capacitive than normal coax.

Hi carlos,

Why do you say that a semi-balanced (2 inner wires plus a shield, connected on one end) cable is more capacitative than normal coax?

Which capacitance are you measuring:
* between the 'hot' and 'ground' inner signal wires?
OR
* between the 'hot' wire and the shield?

Regards,

Andy

[folkdeath95]

Hello,

This is my first post here, even if I've been reading this forum for a long time.
I read carefully this thread but my electrical skill being near zero, there are some things I don't understand.
I'm using a Goldring 1042 cartridge on a SME 3009 S2 Imp, followed by a Project Phonobox. I went on Hagtech page and entered the cartridge inductance (570mH) and the total capacitance of preamp+arm cables (120pF+127pF). The result is a peak resonnance at 13.4kHz, which is crap because it's in the audible frequencies. But looking at the result of the load resistor result, it says 48kOhms, very near near from the standard 47kOhm... So I don't understand waht I've got to do for a good cartridge loading Am I missing something?

[mlloyd1-diy]

carlosfm:

great work as usual. i'm replacing a cartridge finally and need to optimize performance so this information was just what i needed.

for what it is worth, i'm getting a shure m97xE for a denon 37f table.
as potentially useful data for others, my turntable wiring from arm (original arm, original wiring, no headshell attached) through rca output plugs is 124pF per left/right side.

mlloyd1

[Werner]

Here's the M97xe. Measured, not simulated.

The resistive load was 47k. The wiggle at 10kHz is on the test record.

[mlloyd1-diy]

werner:

thanks for sharing the data. i made a wiring change that got the turntable capacitance down to 48pF.

mlloyd1

[Werner]

Hello,
The Spice simulation program that CarlosFM used, seems to differ somewhat from the Hagtech results.

And both are near-useless as they don't take the (inevitable) cartridge's
mechanical resonance and treble losses into account. With MMs this is all
happening around 10-20kHz, and electrical resonance (through loading) is used to compensate for this.

[Werner]

Mechanical resonances and mechanical treble losses (how fast can you wiggle a given mass?) don't show up in electrical models of cartridges. Both phenomena happen between 10 and 20kHz with MM cartridges.

Sadly cartridge manufacturers don't publish the electrical equivalents
of their products mechanical properties.

[Werner]

McCormack Audio..which was sold to Audio Research years ago

At the risk of confirming (part of) my reputation ... surely you mean Conrad Johnson?

[JollyJeweller]

Loading question.
I use a Whest PS.20/MS.20 phono stage which comes with external loading plugs that you plug into the rear of the unit.
The standard plugs are 100 ohm for the M/C input.
I've changed from an Ortofon Kontrapunkt C to a Koetsu Rosewood, do i need to change anything ?
Ta.

[JollyJeweller]

Many thanks, that answers my question!
Good review too