[atkinsonrr]

Wayne-- I have a Duet and am curious about your digital mod to the Duet.  On your site I believe it says you remove everything from the digital signal path.  Does that mean everything after the U04D Inverter?  And I'm assuming this means you do not use a transformer (such as the oft-mentioned SC 947-02).  Have you tried the sound with and without transformer, and if so, what are your findings? 

[Wayne1]

I do not use transformers in any of the digital mods. It is VERY hard to physically fit a transformer without removing certain parts that will cripple certain aspects of the DUET or SB3, like full access to all Internet radio or optical output.

I have tried a pulse transformer in my early days of modding the SB2. I removed it after I found more RFI entering the signal path. It sounded quite a bit worse, to me that not using a transformer. The wiring to and from the transformer was acting as an antenna for all the RFI put out by the internal switcher, wireless card and display.

There is even less room inside the DUET to perform any mod.

So far, I have found more audible improvements by using a high quality linear PS than by adding things in the signal path.

I have also found rather large audible difference between different linear power supplies.

[atkinsonrr]

Thanks for your insights Wayne. 

Just yesterday I decided to go ahead and see what I could do with the Duet.  I managed to squeeze an Eichmann true 75 ohm RCA fed by an SC974-02 loaded with 100 ohms into the Duet case.  I only removed the inductor and the 107 ohm resistor down stream of the inverter.  Upped the DC storage cap to 440 and also employed some ERS cloth and rope caulk damping to the super-light plastic case.  It is now sounding significantly better than stock. 

You are right about RFI it is important to keep any extra wiring as short as possible and use shielded coax carefully prepared.  Using the Eichmann, I was luckily able to mount the transformer directly to the jack.

Earlier, I scored an Accopian Gold pwr supply from Ebay (the Gold series is spec'ed at only .25 millivolt ripple).  That did improve the sound, but not as significantly as the above internal mod.