What effect does cartridge loading have on sound?

I just bought a grown up turntable (VPI HW19 w/ Souther Linear tracking arm)to replace my trusty old Dual 616Q. It came with a cartridge labelled "Souther," which the seller believed to be a moving coil unit made by Benz. The thing is I am running it through the phono section of my 20 year old Harman Kardon receiver, which has no provision for changing resistive loading or capacitance, and says it is for MM only. Oddly enough, the system sounds pretty good. What I'm wondering is what effect changing the loading has on the sound. I thought MCs were supposed to have loading at around 200 ohm, and MM 45K ohm.
Major upgrade!! Well, at the moment you have a "mystery cartridge" but I'm sure you could research its particulars -- besides here and Google, try asking on Audio Asylum.

I wonder if it's a Clearaudio Wood MM cart. It would have to be a MM cart or (very unlikely,) a high output MC cart to drive the HK phonosection. If it is a MM cart (and I'm 99% sure it is) then you don't need to adjust loading, they all operate at 47Kohms which you HK has by default. MM carts ARE sensitive to capacitance, but if it sounds good leave it alone.
Hi, I honestly have no knowledge about this "Souther" Cartridge you have, and as nsgarch explains, it's probably unlikely that it is a high output MC Cartridge. (Due to the fact that you seem to have sufficient gain, and you don't mention that you have to crank the reciever's volume control really high to get acceptable volume levels)

Most MM Phono stages in older recievers generally accepted-were compatible a MM Cartridge with output between 3.5Mv-5Mv.

Even let's say if you were running a high output Benz Micro Glider (Like I myself have) with an output of 1.8Mv, I think you would find insufficient volume, and a drastic mismatch of volume levels versus other outputs (ie: FM, Aux, etc) on your reciever.

There may be the possibility of finding a model number of this Cartridge by unscrewing it from the headshell, and looking in between, on the Cartridge's topside?
Once you could possibly find this out, more information would be likely to be known about it.

Hope this helps, enjoy! Mark

Thanks for your response. It's definitely not wood,it's a solid shiny black color, metal or plastic. The store that sold it to me got it on trade form the person they sold it to years ago, so I wouldn't completely dismiss the notion that it's a MC. What happens when you plug a MC into a MM input? Does it play at all? Play very quietly?
While it sounds good, it doesn't bowl me over with the things that analog is supposed to. Compared to my Dual, it has better resolution, much better bass, more spaciousness, but somehow also a glassiness and not quite natural sound. It isn't as continuous or coherent as it should be. Could this be the result of improper loading? Or a cartridge that needs replacing (the cartridge was a bonus - I didn't even know it had one until I picked up the unit, & I was told that it was old and may need replacing)?
Well, like I said, if it plays through your MM input at levels similar to your CD or Tuner at a given volume, chances are 99% it's not a MC but a MM.

That said, there is a class of moving coil cartridges that the manufacturers (who make them) call Hi Output or "H" or "HO". They have outputs in the 1.2 - 2.5 mV, about the same as a typical moving magnet cart. (Regular MCs are 0.24 - 0.85 mv.)

Your mystery cartridge MIGHT be a hi output moving coil type, and there's really only one way to tell without test equipment, which is: MM carts have no magnetic attraction to small screwdrivers, paper clips, nail files, etc., because their magngets are so tiny. MC carts can exert a very strong force on any ferrous material closer than an inch (use the stylus guard!)

Hope that clears up the confusion ;--)
Great ideas - If I tilt the arm up, it allows the cartridge to pivot side to side on its little arm. Putting a small jeweller's screwdriver within 1/4" of the cartridge causes it to swing toward the screwdriver. Moving the screwdriver away lets the cartridge swing back to its naturl position (the arm in its raised position is a little past vertical, so the sub-arm swings to the right).

Also, the cartridge has a big gold V in the front, with what looks like a figure 8 knot (square knot? I was never a boyscout) above the V. I was mistaken about it being labelled Souther. Souther is printed on the headshell above the cartridge.

The output is definitely lower than my Ortofon, and I had to bump the gain on my Pass pre-amp to high (I think a 10dB gain), but having done that, it's plenty loud.

Any more suggestions?

"I was mistaken about it being labelled Souther. Souther is printed on the headshell above the cartridge."

You had us all scratching our heads real good with that one!!

Anyway, somebody help him out here -- I know I've seen that cart before, someone else's memory working better than mine today?