When evaluating an HDMI amplifier (also known as a signal booster or repeater), you must prioritize bandwidth and resolution support. Ensure the device supports at least HDMI 2.0 (18Gbps) for 4K@60Hz stability, or HDMI 2.1 (48Gbps) for 8K applications. Additionally, verify HDCP (High-bandwidth Digital Content Protection) compliance, specifically HDCP 2.2 or 2.3, to ensure compatibility with encrypted content from streaming devices and Blu-ray players. For long-distance transmission, look for units that utilize active signal equalization to minimize jitter and signal degradation.