Quote Originally Posted by kaushik741 View Post
Hi Feanor ,

Thanks for the reply and mail . I had also reverted back to your mail .

Just to be clear about the FR/EMI factor , as the PSU is outside the unit shall RF/EMI still can affect the audio output if same PSU is Used .

For OPAMP , did you tested LM 4562 or LME49720 ?

....

Regards

Kaushik
So I tried replacing the OPA2134 opamps in my SMSL SD-1955 with LME49720's. The LME49720 is a recently, highly touted opamp especially developed for audio applications.

I listened for about 4 hours in total which ought to be enough to burn in a tiny component such as an opamp. My strong impression is that while the LME49720 is sounds transparent, the top highs are far too shrill for my liking -- this might not be the cases with a different downstream amp than my Class D Audio SDS-258. As typical of class D amps, (I'm sure there are exceptions though), the SDS cuts no slack for harsh records or upstream components.

So I wasted no more time listening to the LME49720 and rolled two of the three, i.e. the I/V / gain pair, for my trusty paired OPA627's. Yes, opamps do sound different from each other. The OPA627's are distinctly smoother on the top end and much more listenable at least in combo with my components. I suspect I do loose some resolution and perhaps transparency with the LME49720 though.

I'm thinking the OPA627's are maybe just too smooth and I might go back to the OPA2134's as the best compromise.

By the way, I'm currently using my SMSL SD-1955 because my Schiit Bifrost is back at Schiit Audio being fitted with the Uber Analog upgrade. See the August '13 edition of Stereophile where in the reviewer stated that the Bifrost offered the best value for money of any component he had reviewed.