Benchmark to amp direct question?

Depends on the preamp. Most separate preamps are much better than the stock unit. With volume control mods however, it can be quite marvelous. It trounces my fully modded Mark Levinson #38, which I thought was quite transparent. Have to keep getting up to adjust the volume, but it's worth it for the sound quality.

Steve N.
Empirical Audio
Manufacturer

Bob_reynolds - the output impedance of the balanced outs depends enitrely on the jumper settings. The place that I set them makes the impedance 30 ohms, just right.

steve N.
Empirical Audio

Bob_reynolds - this high RCA output impedance is only in the older versions, more than three years old. The new cisrcuit board has new buffers and does the voltage divider between buffers rather than at the output pins. The new RCA output impedance is 30 ohms, a bit too low IMO.

Steve N.

Cmk - the DAC-1 converts single-ended to balanced at the output drivers. I would not call this a balanced DAC, but I suppose there are other interpretations.

Steve N.

Bob_reynolds - when I first started modding DAC's I put no additional resistance on the outputs. What I found was that with high-Q or low-loss cables connected, this evidently caused transmission-line type reflections on the cable which could take a while to damp-out whenever there was a HF transient in the music. My theory is that these reflections cause the output drivers to go non-linear at times, which affected the audio range.

If I approximately matched the characteristic impedance of the cables (like you would do in a RF system), the sound improved dramatically at the high-frequencies. Most analog cables are in the range of 75-120 ohms characteristic impedance, never as low as 30 ohms.

There are other engineers that have tried this and reported similar results.

Steve N.

Bob_reynolds - I dont believe that the impedance mismatch and the resulting reflections directly affects the audio band. This is a secondary or indirect effect of some sort. May not happen with tube outputs.

Adasilva - on the recent DAC-1's, using the balanced outputs as single-ended is the same as using the RCA outs.

Audioengr
Have you actually tried to listen to both outputs before concluding that they are the same?

Of course. I mod a LOT of these, so I listen to them continually.

The folks that are reporting better results probably have the older DAC-1 that has high-impedance RC outs. The newer units have low impedance on both Balanced and RCA's, and separate buffering as well. The buffers/drivers are identical on both.

Steve N.
Empirical Audio