Why does Computers - Amp - Speakers sound better?


I have a budget system. Denon turntable, Shure cartridge, NAD integrated amp, and Wharfedale speakers. For some reason, computer -> amp -> speakers sounds SO MUCH BETTER than turntable/cartridge -> amp -> speakers, even when the source file on the computer is 256 kbps mp3.

I don't know why this is. It would make sense if my amp and speakers were leagues above my turntable or if the source file was in 320 or FLAC, but that's not the case. 256 kbps should not sound better than high quality vinyl of music from the past five years (i.e. not mastered from bad tapes).

Is my turntable or my cartridge (or both) inferior to my other equipment? Also, I'm using Monoprice cables for my computer ---> amp and off-brand cables for turntable ---> amp. Could that be why?

thank you. The reason why this bothers me is because I spent over 1000$ on my vinyl (not just for the better sound, but because I'm deeply involved with the new-wave punk scene) and $400 on my turntable/cartridge and it bothers me that a low-quality file produces better sound.
toxicwaterfront
It's a lot clearer and I can hear more things. With vinyl, it's like the music is masked behind a veil, and with digital, the veil's been lifted. Don't know how else to describe it.

My NAD doesn't have a phono input. For my analog system, I'm using the built in phono on my Denon. I'm starting to think it's either that or my cartridge. I've level-matched and listened to about a dozen different records and their respective source files. Only once has the vinyl sounded better than digital, and that was only because it was a very busy ska record and the vinyl helped me distinguish the individual instruments.
And yes, I'm listening to the same album on both vinyl and digital. I'm not comparing two different ones, lol.
Took a quick look at the owner reviews on Amazon and noticed, as I suspected, that most are bypassing the built in Preamp and using a external phono amp of better quality. While I don't believe you have to spend $$$$$ to get good sound, it is asking a lot of a turntable/Preamp combo at that price to be better than digital.

I listened only to cheap turntable's and whatever phono was in the receiver until I was around 30 years old, and when CD's came out they sounded better than what I had been listening to, so I changed to CD's. Twenty years latter,after purchasing a good preamp, one with a good MM phono stage, I purchased my next turntable and am really enjoying my 1000 lp's I had stored all that time.

A while ago I set up my old cheap Rotel turntable into my mid 90's Onko receiver and guess what? It was horrible . The phono stage is very important, and cannot be overlooked! Everything is important!

I would read the many thread's on good budget phono amps, and save my penny's until I could afford it, or purchase a good old Preamp or receiver which is known to have a good phono stage in it.

Sorry for the long post. Good luck

Danny
I'm still curious to hear how you are getting your 256k files to your speakers. Your NAD doesn't have an internal DAC, does it? That means you must be using an external DAC. Are you using Mac or PC? Optical or USB? Do you use a USB/SPDIF converter? You've detailed out what gear you have on the vinyl-based side, it would help to hear what you're using on the digital side. Just to get the full big picture, thanks.