High Output Current Drivers
From Benchmark
What Are 'High-Current Output Drivers'?
The new DAC1 USB features high-current low-distortion output drivers on both the RCA and XLR analog outputs. These drivers incorporate the new LM4562 opamp and are capable of driving loads as low as 300 Ohms without an increase in distortion. This new opamp is unsurpassed in its ability to drive low-impedance loads. In contrast, most audio outputs exhibit an increase in distortion whenever the load impedance is less than 1000 to 2000 Ohms.
The DAC1 USB is well suited for driving long cables, vintage 600-Ohm inputs, and unusual loads. Some audiophile devices have very unusual input stages and can benefit from the robust drive capability of the DAC1 USB.
The classic DAC1 is well suited for driving standard professional audio inputs having an input impedance of greater than 1000 Ohms.
Most modern professional inputs have an input impedance of at least 20,000 Ohms and are designed to be driven from low-impedance outputs. Most modern professional outputs have a source impedance of 100 Ohms or less and are intended for driving high-impedance inputs. This combination of low source-impedance and high input-impedance produces a robust interface that maintains high bandwidth, low noise, low distortion, immunity to interference, and improved common-mode rejection.
It is important to note that most low-impedance outputs are designed to drive high-impedance inputs. In most cases distortion will increase and headroom will decrease when driving vintage 600-Ohm inputs.
Output impedance and minimum load impedance should not be confused. An output impedance of 60 Ohms does not imply that the output can drive a 60-Ohm load. When possible, low-impedance outputs should not be used to drive any input with an impedance of less than 1000 to 2000 Ohms unless they are specified for driving lower load impedances. The DAC1 USB XLR and RCA outputs are designed to drive loads as low as 300 Ohms without an increase in distortion.
All DAC1 converters include an internal HPA2™ headphone amplifier that has an output impedance of less than 0.1 Ohms. Most headphones have an input impedance of 60 to 600 Ohms. The HPA2™ headphone amplifier easily drives two 60-Ohm headphone loads without an increase in distortion. The HPA2™ delivers the full performance of the DAC1 into the very difficult loading presented by headphones.
The DAC1 has become known for its superb accuracy and dynamic range. The output drivers on the DAC1 USB are capable of maintaining this performance when driving difficult loads and/or unusually long cables.
