Benchmark Discusses What Makes a Good Preamp
An Impossible Engineering Task?
Our goal was to produce an analog volume control with the highest achievable transparency. We wanted to be able to place this volume control in front of our AHB2 power amplifier or in front of our THX-888 headphone amplifier without diminishing the performance of either device.
Our volume control would need to have lower distortion and lower noise than either of these amplifiers. Given the extraordinary performance of these THX-AAA amplifiers, this would not be an easy task!
Our unique solution is a fully-balanced, low-impedance, relay-controlled attenuator with over 256 steps. Nothing like this was ever built, and nothing else matches the performance of the Benchmark analog volume control system used in the LA4 and HPA4 products.
The LA4 is not Just a "Good Preamp"
The LA4 was an all-out effort to build the best line-level preamplifier on the planet.
"Benchmark's LA4 is the widest-bandwidth, widest-dynamic-range, lowest-noise, lowest-distortion preamplifier I have encountered." - John Atkinson
Watch as Benchmark's lead Engineer, John Siau, takes us on a deep dive into the relay-controlled preamplifiers inside Benchmark's LA4 and HPA4.
Also in Live Video Tutorials
How Loud is the Distortion from Your Power Amplifier?
In this video, John Siau extracts the data from the published test results of 7 top-rated audiophile power amplifiers. Hidden within the THD+N vs. Power graphs are the answers to two key questions:
- How loud is the noise produced by my power amplifier?
- How loud is the distortion produced by my power amplifier?
Your Amplifier THD+N may be Louder than a Washing Machine!
Don't take our word for it! The evidence is captured in the hundreds of test reports compiled by Stereophile Magazine. Unfortunately, we cannot see this information when looking at traditional THD+N graphs. We need to extract the raw data from the Stereophile graphs and do a bit of math.
John Siau shows that the distortion produced by some of these top-rated amplifiers is louder than the noise that would be produced by having a washing machine in the middle of your listening room!
You wouldn't put a major appliance in the middle of your listening space, so you may want to take a careful look at your power amplifier.
Traditional THD+N Measurement Units Hide the Truth!
THD+N is usually plotted in terms of percent. This is a problem because percent is not a measure of loudness, nor is it a logarithmic unit. If we plot THD+N in terms of loudness (dB SPL) at the listening position, we can easily visualize the noise floor of the amplifier, and we can read the loudness of the THD directly from the graph.
Amplifiers are the Weak Link in the Electronic Chain
In most systems, the power amplifier will generate more THD+N than all of the other electronic components combined. It is time to take a fresh look at amplifier perfomance measurements. The evidence is hiding in Stereophile's test reports!
Feed-Forward Correction Explained!
Feed-Forward Error Correction
Don't look back, the future is here!
Benchmark's AHB2 power amplifier has a unique feedforward error correction system that cancels distortion before it reaches the speaker terminals. In contrast, global feedback systems attempt to correct the distortion after it reaches the speaker terminals.
Feed-forward correction is fast, precise, and inherently stable.
Benchmark's AHB2 blends feedback with feed-forward correction to leverage the best characteristics of each.
Listen to Gene and John as they discuss this revolutionary technology.
- How does the feed-forward system know what correction to send?
- Does it predict the future?
- What makes feedback unstable when driving capacitive loads?
- Why is feed-forward stable when driving capacitive loads?
Take a few minutes to learn how feed-forward error correction works:
- Watch as John provides an easy-to-understand analogy for feed-forward error correction.
- Join the discussion.
- We reserve the right to limit negative feedback.
What is the Purpose of an FFT in Audio Measurements?
The FFT … an Audio Microscope.
An FFT analyzer is like an audio microscope. It allows us to easily measure the frequency and amplitude of tones that are below the level of the noise. Traditional audio meters fail when the signal is lower than the noise level, but with an FFT, we can accurately measure tones that are 30 to 40 dB below the level of the noise.
In many ways, our ears behave like an FFT audio measurement system. Our ears can detect the frequency and amplitude of tones that are as much as 30 dB below the ambient noise. This means that our ears are 30 dB better than traditional audio meters! This is why we can carry on a conversation in a noisy room, and this is why we can hear individual instruments within an orchestra. This is also why small defects need to be detected and corrected when designing top-quality audio gear.
John Siau, Benchmark’s lead Engineer, will explain the “magic” of the FFT analyzer without the use of advanced mathematics. He will show an FFT analyzer in action, and he will measure a complete Benchmark chain to determine if it produces audible noise or distortion. Learn how to read an FFT plot and learn what to look for when selecting audio components.