Upsampling with no interpolation

Read the website, it is all explained….

I did. The chip does an internal bit reduction using a delta-sigma modulator, after the oversampling filter. That cannot by bypassed.

I’d love to see Amir’s measurements of the DDDAC 1794 NOS DAC. From reading the site, it looks like these folks had a lot of fun and did a lot of listening. But, I did not see them sharing any measurements.

I think an audio component that is built entirely by ear or entirely by measurements will be somewhat compromised. Good engineers use both. But, for DIY hobbyists, the journey is at least 80% of the fun.

I guess I missed it, but even after reading the entire story, I did not see any mention of a need for zero-order hold upsampling. The 24/192 tracks they used for testing came from Linn and were already in that format…not upsampled.

I’ve not looked, but I assume Roon is using Naoki Shibata’s SSRC algorithm or similar for sample rate conversion. This algorithm achieves a S/N ratio of 123.15dB and THD of less than 0.00001%. It’s unlikely that any downstream analog component will limited by this performance.

My concern with this feature request is that some users will turn it on, be disappointed with the sound, and then file a bunch of support tickets to Roon Labs.

There are some measurements posted there, but no SNR or THD. PCM1794A is already a terrific DAC, no tweaks needed. (The internal sharp roll-off filter is really good). If DDDAC supports all common sample rates, I don’t see the need for zero hold up-sampling. Anyway, not that I care for NOS, but a DAC that features “a five-level, third-order delta-sigma modulator operated at 64 fS” (quoted from the datasheet) is not NOS by any standards.

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