That's a much better idea than what I was thinking -- I was going to suggest gently twisting a wood screw into what was left of the RCA phono plug and using that to pull the center core out.

Using the line in jack takes the time pressure off and greatly increases the chances of finding an easy way to get the plug out smile

M60ti, VP180, QS8, M2ti, EP500, PC-Plus 20-39
M5HP, M40ti, Sierra-1
LFR1100 active, ADA1500-4 and -8