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by John Siau February 04, 2016 2 min read
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.
More information on headphones and headphone amplifiers can be found here.
by Benchmark Media Systems June 06, 2023 2 min read
At the 2023 AXPONA show in Chicago, I had the opportunity to see and hear the Hill Plasmatronics tweeter. I also had the great pleasure of meeting Dr. Alan Hill, the physicist who invented this unique device.
The plasma driver has no moving parts and no diaphragm. Sound is emitted directly from the thermal expansion and contraction of an electrically sustained plasma. The plasma is generated within a stream of helium gas. In the demonstration, there was a large helium tank on the floor with a sufficient supply for several hours of listening.
by John Siau June 02, 2023 2 min read
I asked ChatGPT to review the Benchmark AHB2, and I was shocked at the results!
It turns out that ChatGPT wrote a review by gleaning information from the many publicly available reviews of the AHB2. I recognized phases and sequences of words that had appeared in prior reviews, and yet the text was new, original, and well written. The ChatGPT review seemed to summarize the collective impressions of the reviewers without directly quoting any particular reviewer.
It should be possible to ask ChatGPT to write a review on any well-known product and the result will be an AI-generated review that reflects the collective opinions of many human reviewers.
These AI-generated reviews may be more useful than traditional search results!
If I am not mistaken, ChatGPT seems to have golden ears!
Here is my dialog with ChatGPT:
John Siau:
Write a review of the Benchmark AHB2 complete with listening impressions.
ChatGPT:
Title: Unleashing Sonic Purity: A Review of the Benchmark AHB2 Amplifier
Introduction: The Benchmark AHB2 amplifier has gained a reputation for its exceptional audio performance and unwavering dedication to sonic purity. In this review, we delve into the heart of this powerhouse amplifier, exploring its features, design, and most importantly, the listening impressions it evokes...
by Benchmark Media Systems May 30, 2023 7 min read
Today, Benchmark's John Siau and OpenAI's ChatGPT had a conversation about star-quad cables. It turns out that ChatGPT got quite a few things wrong, but learned quickly when these errors were pointed out by John Siau.
ChatGPT is quick to recognize mistakes, and quick to provide detailed corrections. In each of the first few corrections, additional errors were made. As each of these were pointed out, ChatGPT began to provide accurate information.
Here is my conversation with ChatGPT:
John Siau:
How do star-quad cables reject interference?
ChatGPT:
Star-quad cables are designed to provide improved rejection of ...