Z&H Designs HO8 All-Discrete 8-Channel Mic Preamp

The HO8 All-Discrete 8-Channel Mic Preamp from Z&H Designs is a high-voltage, mastering-grade microphone preamplifier designed for demanding recording environments ranging from orchestral sessions to everyday tracking. Built around an all-discrete analog signal path with 24 high-voltage op-amps and a 56V linear power supply, the HO8 delivers up to 75 dB of gain with exceptional balance, clarity, and headroom. Its transparent yet expressive character makes it equally capable of pristine capture and subtle tonal shaping across a wide range of sources.

Key Features

• All-discrete analog microphone preamp with eight independent channels.
• 24 high-voltage discrete op-amps for extended bandwidth and dynamic range.
• Up to 75 dB of microphone gain in precise 5 dB stepped increments.
• Ultra-precise gain matching across all channels for consistent multichannel recording.
• Linear trim-matching control with ±5 dB range for fine gain adjustment and character shaping.
• Clean and transparent signal path with the ability to introduce subtle harmonic character.
• 48V phantom power, pad, polarity invert, and 100 Hz high-pass filter on every channel.
• Neon dB metering with a curved anodized front panel design.

Circuit Design & Sonic Character

• All-discrete circuitry throughout, avoiding IC op-amps in favor of high-performance discrete designs.
• Original Z&H “Zen Core” architecture using bipolar transistors for clarity and musicality.
• Capable of maintaining transparency even at extreme gain levels.
• Optimized for acoustic instruments, vocals, orchestral recording, and ensemble tracking.
• Linear trim-matching control enables subtle saturation and tonal variation when pushed.

Utilities & Workflow

• Stepped mic gain control in 5 dB increments for repeatability.
• Linear trim-matching control in 10 dB intervals for fine-tuning gain structure.
• Per-channel 48V phantom power, pad, polarity inversion, and 100 Hz high-pass filter.
• Designed to handle bands, orchestras, choirs, and multi-microphone sessions with ease.

Power & Build Quality

• 56V high-voltage linear power supply for increased headroom and reduced noise.
• Carefully optimized PSU and layout for low distortion and consistent performance.
• Each unit extensively tested and verified for channel-to-channel consistency.
• Handcrafted construction with final testing performed by experienced engineers.

Specifications

• Channels: 8
• Gain Range (Mic Input): 10–75 dB
• Z&H Trim Range: −5 dB to +5 dB
• Maximum Output Level: +26.5 dBu (100 kΩ load, 0.1% THD)
• VU / LED Meter Green Threshold: −14 dBu
• VU / LED Meter Red Threshold: +24 dBu
• Distortion & Noise
• THD+N @ 20 dB Gain, +20 dBu Out: <0.005%
• THD+N @ 40 dB Gain, +20 dBu Out: <0.008%
• THD+N @ 60 dB Gain, +20 dBu Out: <0.048%
• Intermodulation Distortion (IMD): <0.021%
• Equivalent Input Noise (EIN, 200 kΩ Source): <−95 dB
• Equivalent Input Noise (EIN, 600 Ω Source): <−95 dB
• Performance
• CMRR: 41.4 dB at 400 Hz, 1 kHz, and 10 kHz
• Phase Deviation (HPF Off): >4° from 50 Hz to 25 kHz
• Frequency Response (−3 dB): 4.5 Hz – 390 kHz (Mic Input @ 40 dB Gain)
• Frequency Response (−0.5 dB): 10.5 Hz – 140 kHz (Mic Input @ 40 dB Gain)
• Impedance
• Mic Input Impedance: 1.7 kΩ
• Ribbon Mode Input Impedance: 1.2 kΩ
• Balanced Output Impedance: 600 Ω
• Unbalanced Output Impedance: 400 Ω
• Physical & Power
• Dimensions (H × W × D): 9 × 44 × 30 cm
• Weight: 6 kg (13.23 lb)
• Power Consumption: 100–240 V AC, 50 W max