To DDC or not to DDC. That is the question.

@hannesdieter @maprik  Internal photos of the Mk I and the Mk II clearly reveal they do not use the same USB card. One difference is the Mk II card has galvanic isolation that is plainly visible from the underside of the PCB. The Mk I specifies the Combo384 card in Merason’s original description for the Mk I, but not the Mk II. The Combo384 is not galvanically isolated. If in doubt, contact Merason directly, but the Mk II description cannot be applied to the Mk I. 

 I asked AI about Merason’s implementation of the Amanero USB card, and received this:

 Merason incorporates the Amanero board but surrounds it with proprietary, high-performance circuits rather than using a standard stock board implementation. 

• Advanced Galvanic Isolation (Capacitive): While the Amanero board itself manages USB audio data, Merason adds a dedicated capacitive isolator module to isolate the I2S signal from the USB card before it reaches the Burr Brown DAC chips. This ensures that noise from the computer or the USB transceiver card itself is not transmitted to the analog stages, a critical step often missed in stock implementations.
• Low-Jitter Clocking Strategy: The USB input is engineered to deliver a low-jitter I2S signal. The design employs two precise oscillators specifically tuned to manage multiples of 44.1 kHz and 48 kHz, which allows the DAC to precisely match the incoming sampling rate and minimize jitter.
• Dedicated Power Supply: Merason does not rely on the 5V power from the USB connection, which is typically noisy. The DAC1 Mk II includes a sophisticated, linear power supply with twelve separate supplies, with dedicated, oversized transformer sections for various components to keep the digital input section fully isolated from the sensitive analog output stage.
• Signal Path Refinement: The USB module outputs an I2S signal that is carefully shielded to reduce electromagnetic interference, contributing to the "blacker" background and improved resolution described by reviewers. 

Key Differences from Stock Amanero Combo 384/768

While the Combo 384 is a high-quality, popular interface (known for its musicality), it can produce significant noise in its stock state without proper isolation. 

• Vs. Stock Combo 384: The stock card is often powered directly by the USB bus (noisy) and may not be properly galvanically isolated from the DAC's analog section. Merason solves this with dedicated linear power and capacitive isolation.
• Vs. Stock Combo 768: While the 768 is a newer card, the Merason DAC1 Mk II focuses on the quality of the signal path and power rather than higher sampling rates. The DAC1 Mk II deliberately caps performance at 24/192 (PCM only) to prioritize sound quality over high-resolution specs, avoiding the "cold" sound often associated with some modern, faster DAC implementations. 

Summary of Improvements

1. Isolation: Capacitive isolation removes USB/computer noise.
2. Clocking: Two precise, dedicated oscillators for clock stability.
3. Power: Clean, separate, oversized linear power supplies.
4. Signal Integrity: Optimized PCB layout to reduce noise and interference. 

If you are looking to understand how these improvements sound, I can explain how the Burr Brown 1794A DACs or the discrete class-A output stage contribute to the overall musical, warm, and highly detailed sound of the DAC1 Mk II. 

@maprik if you figured out what improvements you’re looking for with your digital may be it’s worth its own topic. I know we all have our ways, but I’m not a fan of adding boxes to achieve a questionable change. 
My DAC has a built in network card and that’s what I’m using. I do not miss my streamer with the headache around power cords, usb cables, etc. 

According to Ed Meitner who designed my DAC, the best way to implement the clock is closest to the signal path. I believe that is accurate based on what I’m hearing. 

I would not waste money on more boxes. Buy more good vinyl instead. 

i understand ai can hear up to 50 khz, so you know you can fully trust it -- like 100% certain -- when it tells you what’ll happen in your system if you try a ddc...  

@mitch2  This AI description appears to be a mix of Mk I and Mk II. Whereas the Mk I USB card has the appearance of an off-the-shelf Amanero card, the Mk II does not. The important takeaway for Merason DAC owners is the Mk I and Mk II are not the same, and improvred USB performance appears to be a differentiating feature between the original version and its successor.

All of this is academic to some degree regardless, as a galvanically isolated USB receiver is certainly advantageous, but not a panacea in itself. Galvanic isolation performance varies with individual architecture and DACs with galvanically isolated USB routinely respond favorably to outboard USB isolators/regenerators.