Knowing Nothing About Capacitance...

OK, I've had a table for 5 years now, have tried numerous phono stages and numerous carts, and am enjoying the hell out of my low-fi vinyl system. But after all this time, I'm still clueless about the relationships between cartridge specs and preamp specs.

For example, I'm now using an AT-OC9ml mk ii MC cart -- on the spec sheet it says that this cart's load capacitance is 20ohms. I picked up a vintage Denon integrated amp that I want to try -- it's MC phono section says that it's set for 100ohms. What does this mean? I know I can use the AT with the Denon, but I'm assuming that there will be some compromise in the match. (Whether it's an audible compromise, I have no idea.)

How does all this cart-preamp load matching work? Please keep it simple. I have a PhD, but it' not in anything like this. My scientific understanding peaked in 7th grade (40 years ago) and has gone downhill ever since.

Dear Rich: Maybe you make an error when you write the thread because capacitance is measured in uf not Ohms, Ohms are for impedance. Btw, 100 Ohms will be fine with your cartridge no problem about.

Regards and enjoy the music.
The sound with the Denon should be slightly brighter and more forward than optimum. The degree to which this appears depends on the rest of your system, your set up, and your expectations.

I had a control on my pre-amp which allowed me to change the load on the fly - the results were quite interesting as you heard the sound go from bright/forward at 47K to dark, dull and recessed at 10ohms. The changes were not ambiguous at all but it was clear to me that I actually liked the load to be a little lower than the range recommended by the manufacturer, probably because my speakers were on the bright/forward side.

In your case the cartridge might sound a bit brighter than optimum. If this is so, you might be able to get someone to alter the Denon by putting some resistors in the phono imput which will reduce its imput to 20ohms. I don't know about your Denon - a lot of phono stages have provision for adding/changing resistors conviently to effect a proper match. FWIW.

You can change the load by using simple Y adapters and some loading plugs made from male RCA connectors and resistors of different values. I use this method with excellent results.

These are the adapters:
Dayton Y Adapter

You simply plug the loading plugs into one arm of each adapter, and you plug you phono interconnects into the other arm of each adapter. Change plugs until you find the sound that you prefer.

I made my loading plugs myself, but you can probably have a local tech make them for you.

Credit to Audiogon member Nsgarch, who taught me this method.
Also, you can look up almost any cartridge on Cartridge and see the loading recommendation as well as weight and compliance specs.

BTW, 100 Ohms is a pretty low default loading value, IMO. Most phono sections default at 47kOhms, and some have options at 1000 Ohms, 100 Ohms and 10 Ohms.
Hey Rich, the loading you are referring to is impedance, measured in ohms, not capacitance. Moving coil cartridges are not affected by capacitance. You also cannot hurt anything by having the incorrect loading, just different tonal balance.

You're absolutely right -- I mistakenly said capacitance. The AT-OC9mlii says that the Recommended load impedance is 20 ohms. The Denon says that its MC phono stage is 100 ohms.

By the way, Tvad, the MM phono input for the Denon is 47k.

So, is the initial poster's statement accurate that at 100 ohms on the preamp side my cart is likely to sound brighter than it should?

Thanks to all of you for answering so quickly.
With the cart's >20 Ohm load impedance, and the Denon's 100 Ohm loading, the match should be very, very close to being spot on, I would think.

If the load is too high, the bass could lack a little weight and the highs might sound tizzy. If the load is too low, the bass could get woolly and muddy and the highs could be rolled off. If you're not hearing any of this, then you're good to go.
Great! Thanks.

So why does AT make the OC-9ml with only 20 ohm impedance? The other carts I've seen are all higher. Is it advantageous at all?
Dear Rich: I think that is the load impedance through a step-up transformer.

Regards and enjoy the music.