Which preamp is better C50 or C2500 for MC402?

I don't think you will hear a difference between the C48 and C50. Thec2500 is whole different ballo wax. I sat on the ss/tube preamp fence for a couple of months. Went with a c2500 and am quite happy. Tube pre/ss amp pre magic

I have a 402 and have it coupled with a Audio Research LS26. I had a MX135 prior to the ARC, I did look at the C2300 when I bought the ARC. My point is not to steer you away from McIntosh as I really do appreciate the sound and build quality of their products. But my point is that getting a tube sound influence vs. another solid state, I believe brings the 402 to a new level of performance. Maybe that helps you, or not, but I am suggesting a stronger look at the C2500. YMMV of course.

The C50 and C2500 are roughly equivalent in price and features. As noted by the others, it depends much more on whether you want to go with the tube sound.

I had a C2300 for 6 months and loved it. But. It took about 3 hours or so to warm up and I couldn't leave it on 24/7. It also didn't reproduce some electronic instruments quite as crisply as I prefer.

So, I turned it in on a C50. Does the C50 sound as good on acoustic music from vinyl? No. Does it outperform with Al DiMeola, also from vinyl? Yes. Is the on-board DAC useful? Yes. Do I use it much? No. Does it warm up fast enough to allow me to actually listen to music rather than wait? Absolutely!

Both are superb units built to serve the same market differently. Give some thought to how you listen and what you listen to. Let that be your guide.

Good luck & happy listening!