Is there a difference in sound between a coax cable and an optical one?


I've had 2 separate DACS within the past 20 years, both using a coax cable.  I've had trouble with both with the connections.  They either come loose or disconnect or whatever.  I've always had to go and wiggle the cable to get the sound to come out again.  The older one was an Audioquest cable (long gone) and the one I'm using now is an MIT (probably 12-15 years old).   My plans are to get a new pre-amp with a built-in DAC and if there is no substantial difference in sound, I plan on using an optical cable this time around.   Any thoughts?
shtinkydog
In terms of my Benchmark DAC3,  the manufacturer indicates that its optical inputs are not recommended for DSD or for sample rates above 96 kHz. They cite that optical connections may be unreliable at sample rates above 96 kHz.  For this reason alone I use COAX on my DAC3 and not optical. 
It's not the RCA cable that's a problem.  It's the RCA jack on the DAC.  On many RCA jacks inside, there is a pressure plate which the pin/tip of the RCA plug touches to make contact.  Over time, if there is tension on the cable, it will bend this pressure plate away and eventually there will not be contact between the pressure plate and the RCA tip.  You really won't be able to see this just be looking behind the components.  It is actually inside the RCA jack.
You could always support the rca with a small piece of foam or other neutral material so that the rca stays level with the input.🙂
Tom:  I like that idea.    I'll have to do something.  It's annoying to not get any sound out after you set yourself up with the music and some "suck down" and then..... ZEEEEERO.  Now i have to get up and wiggle and jiggle the cable.  Thanks!