[daniser]

Are you talking about cFeon flash chip near C-Media CM6631 processor? I don't know, probably it's something related to the C-Media chip itself.
The chip I'm talking about is Nuvoton M054ZAN MCU (datasheet) found on the back side of the board.
Yes, I meant MCU FW version 0.64 which is needed by the DSD upgrade kit to work.
And yes, I successfully fixed my unit this way, now it plays DSD and enters firmware update mode flawlessly.

 

[raoultrifan]

I know, it's the noisy ARM chip; because of this I cut the PCB traces and inserted separate rail for DAC's +5V.

However, the microcode for MKii (DSD version) should also uploaded on the DIP8 cFeon chip as well (for those having the MKi version).

 

[daniser]

In this topic I dive into details of repairing affected Essence One units.

 

[blastomorpha]

I'm enjoying my new DT 1990 PRO these days, do you think I should upgrade the opamp in the AMP section to get the most from the headphones, or just buy a new amp and use the E1 only as a DAC?

 

[raoultrifan]

My 2 cents: basd on the type of headphone and its specs I really think that internal amplifier does a very good job. Feel free to borrow an external amp from someone and test it, but I really don't think you'll hear much difference.

After all, LME49720 + LME49860 work very good together and the sound is quite neutral. If you insist, you might swap the LME49720 with something else...perhaps MUSES02 or even MUSES01 or some solid-state opamps, just be sure it will fit in there.