According to the specs for the HT-500, the (original) lead capacitance is 140pF (one sold on Ebay recently in Australia, complete with a pic of the specs), which is too high for CD-4 - apparently lead capacitance shouldn't exceed 100pF for CD-4. However, you can always change the leads for lower capacitance ones - it just requires some soldering skill. Alternatively, just reduce their length, as capacitance is a function of lead length, although you'll still need to solder the RCA plugs back on. Reducing the length by one third would be enough.
-Don