Benchmark DAC1 and DAC2 converters are equipped with Benchmark’s HPA2™ headphone power amplifier. This is a high-current design with very low output impedance (less than 0.1 Ohms). It is capable of driving a wide variety of headphones while achieving extraordinarily low distortion. The full rated performance of the DAC1 is achieved at the headphone jack while driving two sets of headphones. THD+N is less than 0.0003% under full load. The HPA2™ may be the quietest and cleanest headphone amplifier available.
The HPA2™ also has sufficient output level to drive any headphone well beyond normal listening levels. For this reason, the HPA2™ in the DAC1 USB is equipped with gain programming jumpers that can be used to reduce the gain by 10 dB. We recommend using the 10 dB attenuation setting with the Sennheiser headphones.
The HPA2™ in the DAC1 PRE, DAC1 HDR, DAC2 HGC, DAC2 D, and DAC2 DX converters has an additional 20 dB attenuation setting. This setting is recommended for high-sensitivity headphones. Headphones having a low input impedance (30 to 60 Ohms) often have high sensitivity and we recommend the 20 dB attenuation setting for these headphones.
The attenuation is inserted before the HPA2™ headphone amplifier. This attenuator location keeps the output impedance of the HPA2™ constant and very near 0 Ohms. External attenuators should never be inserted after a headphone amplifier as this would change the output impedance.
Proper attenuator settings are important for maximizing the SNR of the headphone monitoring system. With proper settings, the full performance of the DAC2 can be delivered to the headphones for critical monitoring tasks, or maximum musical enjoyment.
When the headphone attenuation jumpers are set properly, a normal listening level will be achieved between the 10 o'clock and 2 o'clock volume control positions. If a normal listening level is achieved below a 10 o’clock volume-control position, the headphone gain is too high, and the attenuation should be increased. If the level is too low at a 2 o-clock volumecontrol position, the headphone gain is too low, and the attenuation should be decreased.
The 0-Ohm output impedance provides outstanding control of the headphone drivers. This improves bass damping, reduces distortion, and flattens the frequency response.
DAC1 and DAC2 converter families were designed from the ground up to be headphone amplifiers with line outputs. The large power supplies in the DAC1 and DAC2 converters are necessary to support the demanding power requirements of the HPA2™ headphone power amplifier.
"Greater love hath no man than this, that a man lay down his life for his friends." - John 15:13
On the evening of July 17, 2022, my oldest son David Paul Siau gave the ultimate sacrifice of love when he knowingly gave his life to save those he loved. He took three shots from a 12 gauge shotgun so that his wife, children and sister could be spared.
David is survived by his wife Christy Siau and their two oldest children, ages 6 and 3. His 18-month old daughter McKenzie was killed within moments of David. I have no doubt that David and McKenzie entered into God’s glory hand in hand.
My daughter-in-law Christy Siau was shot and nearly killed in the incident. We are grateful that she is now out of the hospital making a full recovery.
In the end, my daughter Christina Siau fought the attacker with a knife and prevailed. She sustained many knife injuries and it is a miracle that she lived. She is now out of the hospital and making a full recovery.
We ask your prayers for the healing of physical and emotional scars. We have been overwhelmed by the love people have shown to our family during this difficult time.
Secrets contributor Sumit Chawla recently caught up with Benchmark’s VP and Chief Designer, John Siau to get a little more in-depth on several subjects.
Q: "Benchmark is one of the few companies that publishes an extensive set of measurements, but you also balance that with subjective testing. Can you talk about the equipment, the listening room, and the process for subjective testing?"
Q: "Was there ever a time where you learned something from a subjective test that was not captured by measurements?"
Q: "You conducted some listening tests to determine whether distortion in the “First Watt” was audible. What test material did you use for this, and what did you find?"
Q: "The AHB2 amplifier incorporates THX Audio Achromatic Amplifier technology. When and how did the partnership with THX come about?"
Q: "Linear power supplies have been and remain quite popular in high-end devices. You favor switch-mode power supplies. When and why did you make this switch?"
... and more!
At Benchmark, listening is the final exam that determines if a design passes from engineering to production. When all of the measurements show that a product is working flawlessly, we spend time listening for issues that may not have shown up on the test station. If we hear something, we go back and figure out how to measure what we heard. We then add this test to our arsenal of measurements.
Benchmark's listening room is equipped with a variety of signal sources, amplifiers and loudspeakers, including the selection of nearfield monitors shown in the photo. It is also equipped with ABX switch boxes that can be used to switch sources while the music is playing.
Benchmark's lab is equipped with Audio Precision test stations that include the top-of-the-line APx555 and the older AP2722 and AP2522. We don't just use these test stations for R&D - every product must pass a full set of tests on one of our Audio Precision test stations before it ships from our factory in Syracuse, NY.