any mods to denon 1650ar player?

I owned a 1650AR for a few years, and I agree, it has excellent build quality for the money. After using it for a while, I bought a Dodson DA217MkII-D DAC at a good price on AudiogoN to go with it, which made a noticeable difference in the sound -- better resolution, greater purity, and more precise imaging.

You may want to investigate the pros and cons of investing in an external DAC and digital cable, at various price levels, versus a mod to the player.

Good luck!

Phasecorrect,
I also own a 1650-AR. If I were to list its strengths and weaknesses as a stand alone player, I would say that the player is extremely detailed and has pretty good bass, but is deficient in imaging. So my experience with this player is completely different than yours. If your system is not detailed, I have to think its not the Dennon but something else in your system.
About a year ago I bought an Audio Mirror DAC and I continue to use the Denon as a transport. This is a much better arrangment than using the Dennon as a stand alone player. This improved the soundstage significantly and improved the already good bass substantially. I would say the combo exibits plenty of detail, but reduced a problem I had with listener fatigue. You may wish to consider this as an alternative to putting money into tweeking the Dennon. I think the Dennon still holds its own as a transport (it really is built like a tank). In terms of tweeking the Denon, I'm sort of with Myraj. For now, you might be ok with the Dennon as a transport and adding an external DAC. Otherwise, I'd sell the Dennon and put the extra money into a more recent stand alone player.

IMHO - there are many other players available, that will greatly outperform, and also would be a MUCH better investment of your "mod dollars", than putting $$$ toward that particular unit. Anyone else agree or disagree?
Good luck and Good listening!