DAC2 V2.X Firmware Update - An Inside Look

DAC2 Firmware Update 2.X

Benchmark has recently updated the firmware on the DAC2 HGC and DAC2 L audio D/A converters (Not compatible with the DAC2 DX or DAC2 D). These two models share the same circuit board and firmware. The two products are identical except for the fact that the DAC2 HGC includes a headphone amplifier.

Most Benchmark products have programmable hardware. We use Xilinx FPGA devices (field-programmable gate arrays). These devices provide high-speed high-density digital signal processing, signal routing, and system control. The entire user interface is also controlled by the FPGA. This programmable-hardware architecture provides generous space for system updates, audio decoders, digital filters and other enhancements. 


Firmware version 2.X is primarily an update to the user interface functions. The new firmware is more responsive and is easier to use. It includes some new features and some minor audio performance improvements. The first production version of 2.X is version 2.2. It was released 6/22/2016.

The update adds an Auto-On function and a volume control memory. The update also remaps the volume control so that the relative volume of analog and digital inputs track more precisely over the entire range of the control. The update also adds an additional 2.5 dB of digital headroom on the USB input. With this additional headroom, all of the digital inputs now have 3.5 dB of headroom above 0 dB FS. The increased headroom on the USB input can be advantageous when playing 44.1 kHz (CD) or 48 kHz (DVD) source material.

New Features

Version 2.X adds the following features:

  • Auto-On
  • Volume Memory
  • - 20 dB DIM

The programmable Auto-On feature configures the DAC2 so that it will automatically turn on when AC power is applied. This feature allows the system to be turned on and off with a switched AC outlet. The 12 V trigger output on the DAC2 can be used to start additional audio components. This feature can be useful in professional applications and in home automation applications. This feature is programmed by pressing and holding the power button for 3 seconds.

The volume control setting is now stored in memory when the DAC2 is turned off. This allows the unit to return to its previous volume setting after restarting. This is especially useful in systems that use the Auto-On feature. This feature is also useful in professional applications where a calibrated setting must be retained after cycling the power.

The DIM function is now fixed at -20 dB relative to the main volume setting. At any volume setting, the DIM button will change the output level by exactly 20 dB. This consistent -20 dB attenuation makes the DIM function much more useful and much more predictable.

Performance Enhancements

Version 2.X adds the following performance enhancements:

  • Improved analog to digital gain tracking.
  • Faster volume control servo.
  • Additional headroom on USB input.

The DAC2 hybrid gain control has been refined to improve the volume tracking between analog and digital inputs. Like the prior versions, the hybrid system controls analog inputs with an analog potentiometer while controlling digital inputs with a 32-bit digital gain control. This system uses a lookup table to match the response of the analog and digital volume control systems. This lookup table has been improved in version 2.X. Over the entire range of the volume control, this improvement minimizes volume changes when switching between analog and digital inputs. This improvement in analog to digital volume tracking may be most noticeable at very low volume control settings.

Transitions between DIM and NORMAL volume control settings trigger the motor-driven potentiometer. This control is driven to a precise location by a servo. This servo rapidly drives the knob to the approximate position and then makes micro adjustments to trim the knob position. The settling time of the micro-adjustments is now much faster. In most cases, the micro adjustments are so fast that they are not noticeable.

Prior to version 2.X the USB input had 1.0 dB of digital headroom above 0 dB FS while the other digital inputs had 3.5 dB. Version 2.X provides 3.5 dB of digital headroom on all digital inputs. Low sample rate recordings (44.1 kHz and 48 kHz) often contain intersample overs that can reach a theoretical limit of +3.01 dB FS. Intersample overs can occur many times per second, but most overs tend to be less than the 1.0 dB provided by the USB input on versions prior to 2.X. Nevertheless, some recordings may benefit from the added headroom on the USB input. The update provides enough headroom to handle worst-case (+ 3.01 dB) intersample oversVersion 2.X will handle the most extreme intersample overs without clipping.

Field Upgrade Kit

Version 2.X can be field installed by inserting a memory module into the empty 8-pin socket on the DAC2 circuit board (see photo at left). If the module is added, a jumper must be moved to select the expansion memory. Version 2.X can also be factory installed by flashing the on-board memory. The expansion memory is only required for field upgrades and is only accessed when the DAC2 is in the process of turning on. The expansion module is completely inactive while audio is playing. For this reason, there is no performance difference between factory upgrade and field upgrade options. We recommend the field upgrade for most customers.

How to Order the Upgrade Kit

The field upgrade kit can be ordered online. It includes a memory module, a jumper plug and detailed instructions. If you are located in a country served by our distributor network, you may not be able to order directly from our store. If the checkout option is not available, you will need to call or email our customer service department to order your kit. 

Kit Contents:

  • Detailed instructions
  • Software chip
  • Jumper


Note: The upgrade is not downloadable because it requires the installation of a memory module and a jumper plug. Installation time is less than 10 min.



John Siau
John Siau


John Siau is VP and Director of Engineering at Benchmark Media Systems, Inc.