PF SETTING FOR MC CARTRIDGE WITH SUT

Mofi and T_bone: your post states that pF is generally relevant for MM but not MC cartridges. Would you consider MI (moving iron) cartridges to be in the same category as MM?? My cartridge, a VPI Zephyr, is a MI.

The Zephyr is hooked up to my phono pre with custom cables that have a capacitance rating of 16pF per foot, times 6 foot length, say 100pF. The problem is that the Xephyr seems to ask for no more than 200 pF downstream, but my phono pre alone has an input capacitance of 200pF. Thus, I am about 100 pF over the recommended level.

Any thoughts??? Thanks

MC Cartridges do not like capacitance. You should reduce it to the minimum possible and also use interconnects with low capacitance.

According to theory, moving coils should be immune to capacitance changes. But in audio, theory isnt always right. Trust your ears and leave it set on the setting that sounds best to u. Yes moving magnets and moving iron cartridges behave the same way and they are very sensitive to capacitance, some require low capacitance and others like the shure v15 series require about 400pF to get the flattest response. Check the cartridge mfrs. instructions for a good starting point and then experiment with different values until u like what u hear. As for the guy with too much capacitance in his preamp, I just heard of a way that u can lower the total capacitance by soldering a small cap in series with each of the tonearm leads. When caps are put in series with the circuit the total capacitance drops just like resistance drops when resistors are put in parallel. You can use ohms law to determine what value of capacitance u need to put in series with the phono leads. I have never tried this yet, but it sounds believable according to theory. But in audio theory is not always right! Hope this helps and Happy Listening! Shay

I understand (I think) why the capacitance should be as low as possible for a moving coil cartridge plugged directly into an active gain stage. The OP said he has his cartridge plugged into a step up transformer and the SUT into the MM input on his phono stage. Is it the case that the phono still sees a moving coil cartridge and that the SUT is "invisible" so to speak?

When caps are put in series with the circuit the total capacitance drops just like resistance drops when resistors are put in parallel. You can use ohms law to determine what value of capacitance u need to put in series with the phono leads. I have never tried this yet, but it sounds believable according to theory. But in audio theory is not always right!

Don't put a capacitor in series! A low value capacitor (e.g., tens or hundreds of pf's) will have an extremely high impedance at low and mid audio frequencies and will essentially kill the signal that is seen by the phono stage. A high value capacitor in series will not reduce total capacitance significantly, and will degrade the signal due to non-ideal behavior.

The statement about how the values of capacitors in series combine is correct in itself, but is being misapplied.

Concerning the relevance of load capacitance to low output moving coil cartridges, the response of the cartridge itself within the audible spectrum will be pretty much insensitive to load capacitance. However, greater load capacitance will increase the amplitude and lower the frequency of an ultrasonic resonant peak, which may result in phono stage distortion products that fall within the audible spectrum. See the excellent post by preamp and cartridge designer Jonathan Carr (JCarr) dated 8/14/10 in this thread:

http://forum.audiogon.com/cgi-bin/fr.pl?eanlg&1281468389&openflup&18&4#18

In this case, the presence of the SUT complicates the issue somewhat. While the SUT may reduce interaction between phono stage input capacitance and the cartridge to some degree, it will introduce the possibility of interaction between that capacitance and the transformer itself, most likely with adverse consequences if any.

So the bottom line, as others have said, is that best results are most likely to occur with the capacitance setting at its minimum position.

Regards,
-- Al