Capacitance Question

Djn04,

You can tune this by realizing that the cable capacitance and that which you can set in the LP5.3 make a pair of series capacitors.

C = (c1 x c2)/(c1 + c2)

In theory, since you know the target value for C as 100, and you know the value of the cable, c1, you can then solve for c2 which would be the value you would want from the LP5.

In reality, you may not have a setting that gives exactly 100pF, but you can still use this to understand what you are doing. And, you just might find a value a little different that you think sounds best.

HTH, and good luck.

Hi Dan,

Actually that's not correct. They're in parallel, not in series, so they simply add together.

Cable capacitance is "in shunt" between the signal conductor and the shield or other return conductor, and the phono stage input capacitance is across/between/in shunt with the signal and return connections on the input jack.

Best regards,
-- Al

My apologies! Thanks for the correction, Al. I wanted desperately to find a way to make this work for the OP. I should have pulled out the transmission line diagrams before I opened my mouth. :-)

What's even funnier is that I was just going over last week for 20' IC experiments. I think my internal wiring is corroding faster and faster.

Dan and Al

Thanks for your responses. I've seen a lot of conflicting information regarding capacitance.

What I find interesting is that Clearaudio will sell a cart that wants a 100pF load with a tonearm that has a cable with 177pF of capacitance. It seems you couldn't match the capacitance with the cart unless you cut and reterminated the tonearm cable.

It's probably not a big deal. I moved the jumpers in the lp5.3 from 100pF to 0pF so I should have 177pF going to the maestro. I'm not sure I hear a difference to be honest.

Djn04 -- Load capacitance is usually not too critical, even for a mm, and often a moderate mismatch can be synergistic with the rest of the system.

The differences would be in the extreme upper treble. You may find this Hagerman Technology page to be of interest (although keep in mind that the calculators it provides are approximate, and are based on some simplifying but imprecise assumptions).

According to the cartridge database at vinylengine.com, your cartridge has an inductance of 420mH. Combining that with a load capacitance of 100pf in the Hagerman calculator results in a resonant peak at 24.6kHz, outside of the audible spectrum. Combining it with a load capacitance of 177pf moves the resonant peak to 18.5kHz. At 277pf the peak moves to 14.8kHz.

I don't know about you, but I doubt that I can hear any of those frequencies to the point where I would be able to tell the difference. :)

Best regards,
-- Al