Transport for DAC

My power amp (Rowland 102) has only XLR inputs
rated as 40k impedance. 9pF with 1600 ohms of output impedance makes
fc=11MHz. It has to be something else.

It has to be something else.

I agree 100% - which is why I asked. It does not make sense unless
something else is going on.

The only thing I can think of is ground loop or RF/EM pick up. If you raise the
output impedance of the source to 1600 Ohms then you are surely much
more susceptible to RF or ground loop effects if there is any imbalance to
ground anywhere in the circuit. As you lower the output impedance of the
source you will kill any ground loop or RF/EM signal versus the true signal.

The fact this translates to more dynamics sounds intuitively correct...basically
cleaner sound is likely to sound more dynamic with more
"blackness"...

Kijanki & Shadorne -- Thanks very much for the good comments and info. I looked at the manuals and Benchmark's comparison chart for all three versions of the DAC1, and yes the USB and Preamp versions are the only ones with the "State-of-the-art LM4562 high-current op-amps." The USB version has that op-amp in the output stage only, while the preamp version uses it throughout the analog paths.

A result of that is the 1600 ohm output impedance of the DAC1 with the 10db pad enabled is reduced to 425 ohms in the other versions, although that is still much higher than for the other settings of the attenuation pads.

But I too am mystified as to why the 10db/1600 ohm position should have produced such poor results in Kijanki's setup.

Thanks again for the good information. In my own case, when I make my purchase (probably in a couple of months), I think the choice will come down to the DAC1-USB, or one of two all-in-one cdp's (now there's a way to eliminate transport-to-dac jitter :)), the Doge 6 (tubes), http://www.pacificvalve.us/DOGE6.html or the Sony SCD-XA5400ES, both of which are in the same general price class and have received a lot of excellent comments. It's not worth it to me to go above that price level because around 80% of my collection and my listening is vinyl.

Regards,
-- Al

Shadorne - Thank you - that's probably the case especially with my amp (class D). 0dB setting is OK - it gives full power at about 1 o'clock position of the volume knob. The problem comes when I listen very soft at night. Fortunately volume pot on my Benchmark works from zero with very good tracking - might be coincidence since it doesn't look expensive.

Benchmark do not recommend to use the Volume pot at less than 9 oclock as it may cause slight channel imbalances when used at extremes (same goes for any volume pot actually) - I think I read a comment on Headfi.org by Elias Gwinn about this very topic.

Shadorne - I'm perhaps very lucky with this particular unit. I used more expensive and larger ALPS "Blue Velvet" pot with conductive plastic track and matching was worse than this tiny pot (Alpha I think).