USB DAC's ?

Converting from USB to SPDIF to I2S (computer to digital coax to DAC chip) is not optimal versus a well executed USB DAC which will convert from USB to I2S in one step. In general, the more you convert, the less good it's going to be.

It might turn out that you're quite happy in spite of the extra conversion step, which I think would be terrific because only your ears know.

If you do decide on a USB DAC in the future, amongst the many USB DACs out there, some that I would personally consider are:

Wavelength Cosecant
Red Wine Audio Isabellina
Audio Sector / Audio Zone
Wavelength Brick
UltraFi iRoc

I have either owned or auditioned all of these DACs, presently own the Isabellina and think it is fantastic.

Thank you for the recommendations, I may be wrong (or just further demonstrating my luddite knowledge on digital audio matters !) but I do not think my DCC2 is compatible (connection wise) with I2S.
Nevertheless the goal is to obtain the best possible reproduction through the chain of : hard disc - Mac Mini - Emm Labs DCC2 ?

If you want to continue to use the DCC2 as a DAC, then for the very best possible sound, consider something like this:

http://www.empiricalaudio.com/frComputer_Audio.html#USB%20Off-Ramp

The HagUSB is quite a bit cheaper, but the Empirical Audio product is a premium product. I have not personally auditioned either.

Oh, silly me. In my last response, I forgot about the original post. Sigh. Your original suggestion of the Off-Ramp is a good one.

As for the Benchmark, I do not like the Benchmark sound.

If you're open to using the analog inputs of the DCC2, consider the Red Wine Audio Isabellina, as it is an excellent, dynamic, NOS USB DAC.

I am using a Mac Mini, LaCie Hard Drives into an Epirical Audio I2S Off-ramp, Empirical Turbomod Benchmark DAC1 with op amp upgrades.

The Empirical Audio modded DAC1 is a completely different beast from the unmodded DAC. Vocals are smooth. There is no harshness or reading of brightness. Tone colors are more true and bass to treble transparency greater. No comparison, but also multiple times the cost of the original DAC1.

I can recommend the off-ramp without hesitation. And, I am tremendously happy with the modded DAC.