Originally Posted by hedrick
It's worth considering what is happening inside the computer.
OK, let's play
The digital path from player to sound card is almost certainly different than to an external DAC.
Yes. There is a link, typical Toslink, SP/DIF, Firewire. or USB between the external DAC and the PC.
If the DAC were inside the PC, the link would be very much like SP/DIF or another similar link format called I2S. I2S differs from SP/DIF in that the clocking frequency is separated from the data. I2S or something very similar is far and away the most common internal link format between the DAC chip and the rest of the audio interface circuitry in a PC.
Firewire and USB are highly complex protocols, as compared to I2S.
PCs have a tendency to insert conversion steps,
This is never done gratuitously. If the step is done, it is done in a comparable way for either the external DAC or the internal DAC, all other things being equal.
and the configuration settings are likely to be different.
You have to know all the software well to know when this is happening.
The basic software involved will be the audio player software (e.g. Media Player), the operating system multimedia interface software, the operating system I/O device handling software, and the device driver software for the actual audio interface.
Other than the device driver and any operating services it might use (e.g. USB support if the link to the external DAC is USB) , the software path is identically the same for an internal or an external audio interface.
I would be concerned that using a different path might produce a different result for that reason, and not because of differences in DAC quality.
Since other than the device driver, the path software is identically the same for an internal or an external audio interface, the above statement is simply not true.
I use a Macbook Pro in a fairly good setup. I get better sound from the headphone jack than using a Benchmark DAC-1.
You're talking about your preferences, which are probably based on a sighted, non-level-matched, non-bias-controlled evaluation.
I very much doubt that the internal sound chip is better than the DAC-1.
The DAC-1 's DAC chip probably outperforms the comparable part in the MacBook by one or two orders of magnitude, based on test bench measurements.
Something else is going on.
Yes something else is going on: The sound quality procedure evaluation you are probably using is probably about as erroneous as your theories (above) about the software architecture of your computer.