Input Capacitance of tonearm cable with MM cartridge.

[Chris]

I now use my old A&RP77 cartridge which I have had retipped. I notice that the manufacturer´s specs originally mentioned 400pF as the ideal capacitance for the 47K input on most amps. I understand that this capacitance should be the sum of the arm cable (mine is Cardas in an Ittok by Johnnie) plus that of the cartridge itself prior to the phono stage for optimum results. Most arm cables are around 100pF so I thought of trying to add the difference, rather like the 220pF gizmo that my old Ortofon VMS20E cartridge used to include for its use between the cartridge pins.
Is this worth trying ?

 

[Jim Audiomisc]

Yes. The alternative is to make an 'extension cable' which adds the right amount. Means a longer cable that might affect something else. But easier to swap in/out for a test/trial. However I tend to just solder some caps on the backs of input sockets if they are needed.

 

[Amber Audio]

You can get Lo and Hi Cap phono cables, lots of Van Damme around 55pF, there’s a Morrow Audio PH3 that’s 294pF. A Hi Cap cable lets you keep the length down and reduce chances of interference, plus it looks tidier.

 

[Craig B]

Hi Chris,

Nice to hear that your are still keeping the P77 going.

That was the old Ortofon CAP 210 that you recall using with your VMS MkII. I wish I still had a couple of these in my spares box here. One does occasionally come up for sale or auction on-line, unfortunately, CAP 210 won't span the pins gap on the A&R MMs.

I'd go with soldering caps within a pair of RCA male to female jumper plugs myself. Easy to swap in/out with no substitute tonearm cable 'committal', phono input alteration, nor the potential negative side affects of a longer extension lead pair.

If you'd prefer to experiment with different loading values, another option is to use two RCA 'Y'-pattern splitter cables (2 x female to 1 x male) at the phono input sockets. Different loading plug pairs can be inserted into one of each 'Y' splitter pair with the standard phono leads into the other side. There is a commercial product from dB Systems like this, but these are easy to DIY for a small fraction of the cost. If you do go this route, keep in mind that the cheap 'Y'-cables can add circa 70pF (meaning that you'd want to subtract that amount from each capacitor ordered for a given capacitance result).

Drop me a PM if you'd like more details.

Craig