I have a 4mv Reference Sonata, which simply says "insensitive to load capacitance," and I suspect the Reference is similar in that respect. Also, your phono cable is very short. Both of these factors suggest that you can feel free to add any reasonable amount of capacitance, perhaps up to a few hundred picofarads (pf), without affecting the sound at all.
But it may not be necessary to do that, if a good ground strap would have a similar effect to what you found when you touched the phono preamp. It looks like the best way of getting that, without having to purchase a large quantity from an industrial distributor, is via e-Bay. You can search there under "ground braid." Here is one good example:
http://cgi.ebay.com/20-Tinned-Copper-Braid-3-4-Flat-Wire-85A-Max-Ground_W0QQitemZ370134600553QQihZ024QQcategoryZ26213QQssPageNameZWDVWQQrdZ1QQcmdZViewItem
If that doesn't do the trick, and you want to try adding capacitance, it looks like no one makes anymore the kind of kit I referred to, that I had many years ago, containing a set of capacitors installed on rca plugs. So you'd have to make your own.
Here is one example of a y-cable that you would need; there are many others, as you no doubt realize:
http://www.bhphotovideo.com/c/product/488449-REG/Phoenix_Gold_ARX_569_Silver_500_Series_RCA.html
The most convenient and inexpensive way of getting the rca plugs and capacitors would be, if you can stomach doing so, from Radio Shack. Their part number RSU 11537479 is a set of four gold-plated rca plugs. Part numbers 272-123 (100pf), 272-124 (220pf), and 272-125 (470pf) would be reasonable capacitor choices. Start with the 100pf, and if that doesn't do it go up from there.
You can also find suitable capacitors, with similar values, here:
http://www.tubesandmore.com/
Or if you want to wade through a vast selection of potentially higher quality parts, from an industrial distributor, go to http://www.digikey.com
You would have to be prepared to solder the capacitors to the rca plugs, of course.
But it might be simplest to start by trying the ground strap approach (using it either in place of or in parallel with the ground wires you've tried -- it shouldn't matter which), which could very conceivably solve the problem.
Regards,
-- Al
But it may not be necessary to do that, if a good ground strap would have a similar effect to what you found when you touched the phono preamp. It looks like the best way of getting that, without having to purchase a large quantity from an industrial distributor, is via e-Bay. You can search there under "ground braid." Here is one good example:
http://cgi.ebay.com/20-Tinned-Copper-Braid-3-4-Flat-Wire-85A-Max-Ground_W0QQitemZ370134600553QQihZ024QQcategoryZ26213QQssPageNameZWDVWQQrdZ1QQcmdZViewItem
If that doesn't do the trick, and you want to try adding capacitance, it looks like no one makes anymore the kind of kit I referred to, that I had many years ago, containing a set of capacitors installed on rca plugs. So you'd have to make your own.
Here is one example of a y-cable that you would need; there are many others, as you no doubt realize:
http://www.bhphotovideo.com/c/product/488449-REG/Phoenix_Gold_ARX_569_Silver_500_Series_RCA.html
The most convenient and inexpensive way of getting the rca plugs and capacitors would be, if you can stomach doing so, from Radio Shack. Their part number RSU 11537479 is a set of four gold-plated rca plugs. Part numbers 272-123 (100pf), 272-124 (220pf), and 272-125 (470pf) would be reasonable capacitor choices. Start with the 100pf, and if that doesn't do it go up from there.
You can also find suitable capacitors, with similar values, here:
http://www.tubesandmore.com/
Or if you want to wade through a vast selection of potentially higher quality parts, from an industrial distributor, go to http://www.digikey.com
You would have to be prepared to solder the capacitors to the rca plugs, of course.
But it might be simplest to start by trying the ground strap approach (using it either in place of or in parallel with the ground wires you've tried -- it shouldn't matter which), which could very conceivably solve the problem.
Regards,
-- Al