DAC1 USB as Speaker Preamp on Variable vs. Calibrated Settings.
DAC1 USB as Speaker Preamp on Variable vs. Calibrated Settings.
Submitted by CLG on Tue, 2012-01-31 13:50I'm considering getting a new power amp for my speaker set up and using the DAC1 USB as a preamp. But I've read things on other forums that lean both ways as to which (variable vs. calibrated) setting sound better on the DAC1. I personally haven't heard much different but I just wanted to get an expert opinion on it. Do the two settings sound any different? Should they?
Also, assuming I have the latest firmware on the DAC1 USB, do any of the PRE/HDR models sound different? Is there any different beside the analog opamp circuitry and analog inputs and the remote control? Is there any different in terms of sound quality between all the models?
Sound Quality-Do All DAC1 Converters Sound Alike
Hi CLG,
While all models of the Benchmark DAC1 series share the same circuit design and dac, as we go up the line, premium opamps and connectors are added, along with additional features including remote control. And while you would imagine that the sound quality would be the same, the reviewers find that the upper models are slightly more refined. Measurements, however, are the same.
For a comparison, see http://www.benchmarkmedia.com/dac/dac1-comparison-chart
Best regards,
Rory Rall, Sales Mgr.
Sound Quality - Variable vs. Calibrated
The sound quality of the DAC1 family of converters does not change when switching between "Variable" and "Calibrated" modes. Two identical circuits control the gain. One circuit uses the front-panel volume control. The other circuit uses the 10-turn volume trim pots (located near the rear of the unit). These circuits provide identical performance when operating at identical gain.
The full performance of the DAC converters is delivered at any volume control setting above 12:00 (top half of the rotation). This is one of the major advantages of analog volume control. In contrast, a digital volume control only delivers maximum performance at full volume.
All DAC1 converters have programmable output attenuators on the XLR outputs. These passive attenuators reduce the output level of the DAC1 without degrading the SNR (signal to noise ratio). Use the passive attenuators to place the volume control in the upper half of its rotation at normal listening levels.
If the volume control is in the first half of its rotation at normal listening levels, increase the attenuation.
If the volume is too low at maximum rotation, decrease the attenuation.
Attenuator settings are 0 dB, 10 dB, 20 dB, and 30 dB. 0 dB is the loudest setting (highest output level). Most power amplifiers require the 20 dB pad. All DAC1 converters are shipped with the 20 dB pads enabled.
We highly recommend direct connections between the DAC1 and the power amplifier. Inserting a second preamplifier in the signal chain will reduce the transparency of the audio system.
How To Use the Variable/Calibrated Switch on the DAC1 Series
The Variable/Calibrated switch on the DAC1 series is a valuable feature allowing the user to utilize the DAC as a preamp, or with an existing preamp. When set in the 'variable' position, the front panel volume pot controls the main outs so as to drive a power amp directly, eliminating the need for a separate preamp in the system. Not only does this savethe user the expense of a separate preamp, it may very well improve the system's sound quality with lower noise and distortion. Many Benchmark customers have removed their preamp from the system, using just the DAC1 for system control, and noticed a marked improvement in sound quality.
The 'calibrated' switch position is used when the DAC's output is fed to a separate preamp, giving an output to the preamp similar to that of a CD player. One should never use the 'calibrated' position when sending the DAC's output directly to a power amp, as this will drive the amp to full output, damaging the speakers and quite possibly one's hearing, depending on proximity to the speakers.
In either switch position, the front panel volume pot always controls the headphone output level.