I think that doing Burson is one of the most effective way to upgrade your CD player.

Full Text:

I finished installing 5 pairs of Burson single opamps in my Denon DVD-A1 (DAC chips are 4 x pcm1704) a month ago and have listened to it from then on. As shown in the pictures, the denon uses op amp chips such as 3 pairs of ne5532, a pair of op37 and a pair of op 275.

Installation would be very simple if you are to replace single opamps with single Burson opamps or Dual opamps with Dual Burson opamps. I replaced dual opamp chips the half of which is used with single Burson opamps. I needed to rearrange the pins of single Burson so that it matches the slot for double opamps. It took some time.
My Denon System: The loudspeakers are Guarneri Homage, the power amp is heavily modified VAC R30/30, and the preamp is passive and AudioConsulting Silver Rock AVC (it was TVC. Using only the secondary wiring as AVC improves the sound.)
Before mod with Burson:

The original denon sounded harsh and metallic. It was like so called digital sound.

After Partial Mod:

Just replacing 4 ne5532 opamps for IV conversion with Burson improved the sound a lot.
After Full Mod:

Comparison between cheap opamp chips and Burson’s discrete opamps which costs 5-10 times more may be meaningless if the improvements are small. Replacing all the opamps with Burson’s completely and actually transformed the sound of the denon; the harsh and metallic flavor is all gone. Now it sounds lush, detailed, and smooth. 
I also compared the denon with Burson opamps with my DAC (pcm1704+tube analog stage). Now, the difference between the two almost comes down to the difference between the sound of tube and transistor. Better bass and smoother for Burson, better midrange and voice for tube, etc. But the difference was not great. Both were very musical with harmonics.

I think that doing Burson is one of the most effective way to upgrade your CD player.

Many thanks to Burson.