It seems that some people claim these 2 keyboards are almost identical , while others claim there are noteable differences. I liked the 640 better and heres a writeup about it from a online buying/review guide.


Yamaha DGX640 Review

The Yamaha DGX 640 is very similar to its predecessor the Yamaha DGX 630. There are a few differences though. The Yamaha DGX-640 has more voices, songs and styles, the keys are closer to that of a grand piano than the DGX630, and there are a few technical improvements. It sells for $799.99 online, about US$70.00 more than the Yamaha DGX630. It's really an upgrade to the DGX-630.

end article

so according to this review, the keys are supposed to also be a upgrade.

I was told the 630 is no longer in production and that the 640 is a improvemnet over the 630 .

32 more voices

improved weighted action keys { less noisy and better placement}

more digital effects

a more realistic matte styled finish on the keys

more layering/splitting possibilities

easier USB port access

Is the DGX 630 the one that is equivalent to the YPG 635?

So the DGX 640 also has a YPG equivalent?

I was about to post the same topic. I'm curios if someone actually tested them side by side...

this is what I was lead to believe when I spoke to Kraft music...but supposedly the 640 is a step above both of them.

I'd open up each of their spec pages on yamaha's website in different tabs and check them side by side. Chances are there will be more tones on the 640 among other things.

Hopefully they moved the headphone jack to the front

DGX 630 is equivalent to YPG 635. I don't think the DGX 640 has a YPG equivalent.
I just bought the 604, and the headphone jack is still on the back. I don't understand why they didn't change that.

The 640 also uses a 3-layer piano sound, I don't think the 630 did.