Buy High Pass Filter or KAB RF1?

There is only one line feeding the sub so I’m not sure how I would connect this just to the sub.

Does the problem still occur when the sub is not operating? If so connecting the filter just to the sub won’t help very much, of course.

If the problem only occurs when the sub is operating, though, you could connect the filter between the Marantz and the sub, with a y-cable connecting the bass signal provided by the Marantz to both inputs of the filter, and with just one of the outputs of the filter connected to the sub.

The reason for the y-cable is that I see in the instructions for the filter, which I found online, that there is an "important note" saying that it should never be used with only one of its two channels connected, and "if you must do that" a y-cable should be used to connect the input signal to both inputs. I’m guessing the reason for that might have to do with the possibility that noise occurring in an unused channel as a consequence of having its input unterminated may couple into the channel that is being used. If so, a shorting plug on the unused input could be used as an alternative to a y-cable.

In any event, I agree with Lew that the filter should absolutely not be connected to the output of the cartridge. There are several reasons for that. Just to cite a couple: The hum & noise produced by the filter is specified as "> -85 db ref 1 volt." Since the 5 mv rated output of the cartridge is 46 db less than 1 volt it would mean that hum and noise produced by the filter could be as little as 85 minus 46 = 39 db below the rated output of the cartridge, which would be unlistenable. Also the unspecified and unknown input impedance of the filter stands a good chance of being too low to provide reasonable results when used with a moving magnet cartridge.

Regards,
-- Al

Guys,
I may have figured it out and I would like to get your opinion. The P3 mass is 11 g. My Nagoaka MP-110 cartridge is 6.5 g with only a 6 for dynamic compliance. Using an online calculator this puts the resonant frequency at a 15-16 Hz!I believe it’s supposed to be around 10 Hz correct?
Do you agree this is most likely my problem?

Great insight on the y connector Al!

Also, I cancelled the order for the KAB because I now think it’s a cartridge incompatibility issue with my light tonearm since the dynamic compliance of the cartridge is a mere 6 causing the cartridge resonance to be 15-16 Hz.

It looks like I will be on the hunt for a new cartridge first. 

I posted the following in one of your other threads:

It appears that the Rega P3 is normally fitted with a Rega RB300 tonearm, which according to the listing at Vinylengine.com has an effective mass of 11.5 grams. Also, since the cartridge is made in Japan its dynamic compliance is probably specified on the basis of 100 Hz, rather than on the 10 Hz basis that is usually used by the calculators, such as this one. I would expect that its compliance at 10 Hz is **probably** in the rough vicinity of 10 or so.

Plugging a compliance of 10 into that calculator in combination with a tonearm effective mass + cartridge weight of 11.5 + 6.5 = 18 grams results in a calculated resonant frequency of 11.86 Hz, which is within the 8 to 12 Hz range that is often considered to be ideal.

But note the word "probably" in my statement. It’s hard to say for sure.

Good luck. Regards,
-- Al

Your calculation is wrong. Your nagaoka has 6cu dynamic compliance only when it’s measured at 100Hz just like all japanese cartridges.

For your calculation you must use dynamic compliance measured at 10Hz (not at 100Hz), this is a problem if you don’t know.

Convert 6cu @100Hz to 10Hz

6 x 1.7 = 10.2 cu

this is a compliance of your nagaoka at 10Hz , now you can use this data for calculation of tonearm/cartridge resonance. Actually it can be from 10 to 12cu compliance. The range of RF is 8 - 15hz