John Siau tears down a Benchmark HPA4 Headphone Amplifier and LA4 Line Amplifier to show us what is inside. Fully-balanced 256-step relay-controlled attenuators, feed-forward error correction and much more.
Products Discussed in this Video
The Benchmark HPA4 Headphone Amplifier
- THX-888 Headphone Amplifier featuring Feed-Forward Error Correction
- Entire Signal Path is Relay Controlled
- 256-Step Relay-Controlled Volume
- Lowest Noise, Lowest Distortion Preamplifier Available
- International Power Supply
- High Power Headphone Output
- Independent Line-Level Output
- Certified for Pro or Hi-Fi Applications
- Supports full Studio-Level Balanced Inputs and Outputs
- 0.1 Hz to 500 kHz Bandwidth
The Benchmark LA4
- Identical to the HPA4, but without the Headphone Amplifier
2 comments
Thanks for such an in-depth video.
I use the HPA4 in my mastering studio. It’s my volume knob. The input is from my Trinnov system, whether it’s for my speakers or bypassing the Trinnov for my headphones. It provides the output controller to my amp and speakers. It’s an oddly useful device in a rack-mount version. I love the relays and the symmetrically reliable volume control. The dim feature is perfect! Oh, and the headphone amp is not bad, either! (understatement…)
I really love the FPGA “make before break” concept of the relay switching. Maybe that’s why I never hear any artifacts when controlling the volume.
Great to see the teardown! Something I would love, if possible in future firmware or product updates, would be to expose more of this control directly — either with IR commands like “select input X” and “set volume to -30”, or even better with an rs232 or USB serial connection. That would enable multi-channel use cases with a set of LA4s set consistently. The current IR commands express changes relative to the current setting, so are not robust when controlling multiple devices