Dale Stevens wrote:
What pc volume level do you folks use feeding the dac?? Thx, Dale
This is a very important question, and its answer matters much more than the comparatively subtle differences between DACs.
Any control of volume that a computer (or iPhone, or any such device) is doing is in the digital domain, and must be accomplished by scaling. Mathematically this means multiplication. (If the multiple is a power of 2 bit shifting can be used) Volume is reduced by multiplying all samples by a number less than 1. This reduces the numeric range of the samples, but does not change the quantization levels, which means there are now fewer bits per sample used. This causes the SNR to degrade due to what is called quantization noise. Each bit that is no longer utilized decreases the SNR by about 6dB. This is why digital volume control is not so good.
So to get to the point... We want the digital output from the computer to be as wide a range as possible numerically, ideally the exact same bit stream that was decoded from the source, and not compressed into a smaller numeric range. Typically, setting the digital volume to max accomplishes this, but honestly I can't say for sure if this is standardized on all audio cards.
One thing for sure though, if you're going to attenuate your volume digitally you might as well use a cheap DAC and save money since you have already thrown away signal quality you can never recover.
My advice is use full digital volume only.