Has anyone try the Benchmark DAC1 Preamp?

Cldinsmore, was your DAC1 the DAC1USB?

I asked BenchMark, the difference between DAC1USB and DAC1PRE, other than the extra input, is the premium connectors and more use of LM4562.

Since I don't need the extra analog input, I was thinking that the DAC1USB might be all I need.

No. Mine did not have USB.

Also...It sounds like Amfibius is saying the DAC1 Pre is a digital preamp. The preamp in the DAC1 Pre is analog and so is the volume control. I'm also not sure what he means when he says "every interface you add in a digital system increases jitter." The DAC1 Pre is not adding any additional interfaces. Even if it did, the DAC1 is immune to jitter due to the Ultra Lock system. I would also think that analog signals do benefit from short signal paths more so than digital. Digital signals being '0s' and '1s' are much less prone to contamination. As far as exposing the analog signal to digital noise...the DAC1 Pre is dead quiet and has an incredible S/N ratio.

Cldinsmore I don't know what type of preamp the Benchmark DAC1 PRE is because the literature in their website does not say. Consequently I did not say if the DAC1 PRE was digital or analogue. If you say it is analogue, then you must be better informed than me.

As for "adding an additional interface", what I mean is the connection between transport and DAC. In a one box CD player the connection between transport and DAC is short, and the impedance is matched. With ANY outboard DAC, you have: output jack, cable, input jack. The length and impedance of the cable is not known by the designer, and each cable/jack interface is a major source of jitter.

"Immune to jitter from the data lock system" ... either someone has been reading too much marketing material or Benchmark is able to offer something that even Meitner can not do :)

I would also disagree with your contention that 0's and 1's are less prone to contamination than analog signal. Remember that a 16 bit PCM digital transmission is a square wave transmitted at 1 MHz (by Fourier analysis even higher than this - thanks to H3, H5, H7, and so on). Digital signal is exquisitely sensitive to impedance mismatch. Analogue signal is "only" 20Hz-22kHz. Which do you think would be more prone to degradation?

Thanks for the clarification Amfibius.

As far as the issue of transmission of analog and digital signals go I am certainly no expert. I was just reiterating what I've read...most notably David Rich (EE) and Peter Azel (Audio Critic). Also, if the cable interface is so critical why doesn't Benchmark mention anything on the subject? I have spoken to them regarding cables and they said any decent coax cable will do the job. I have also used a couple different cables and they sounded identical to me. Could you direct somewhere where I might read something on what you describe?

As far as the jitter issue goes, again I am no expert. I'm just going by all the reviews of the Benchmark I have read. They all say that the unit is remarably free from jitter and the unit has been extensively reviewed.

Here is an excerpt from the Audio Critic on the subject:

"Perhaps the most sensitive distortion/noise test is what I used to call the Rob Watts Test (named after Rob Watts, a U.K. engineer), consisting of the FFT spectrum of a dithered 1 kHz tone at –60 dBFS. This is shown for one channel of the DAC1 in Fig. 2. The largest blip sticking out of a bin-by-bin noise floor of –146 dB is no taller than –134 dB. (Is that clean enough for you?)"

They go on to say, "A word about jitter. Some high-end reviewers flap their wings very vigorously on the subject, but as Bob Adams pointed out more than ten years ago in the abovementioned article, there is no reason to single out distortion components caused by jitter as distinct from those caused by other circuit mechanisms. Distortion is distortion, no matter where it comes from, and the tests above cover that ground in sufficient detail. To isolate and measure jitter, one would have to remove the cover and go inside the Benchmark DAC1, because it doesn’t have a digital output (nor does it need one). The instruction manual goes into great detail about jitter, with four different graphs to prove the DAC1’s immunity to it. Just for the hell of it, without much hope of significant results, I ran a hi-rez FFT of a full-scale 20 kHz tone to see if there were any noise sidebands in its vicinity that would indirectly indicate the presence of jitter. As Fig. 7 shows, there weren’t any, at least not under the conditions of my quickie test. And that’s all, folks."