External Clock for Digital Audio

The Gustard C18 is a high-precision 10MHz master clock designed for digital audio systems that can accept an external clock reference. Built around an ultra-low-noise SC-cut OCXO, it delivers low phase noise, strong frequency stability, and both sine wave and square wave outputs for connecting compatible DACs, streamers, interfaces, and other clock-ready components.

Low-noise clocking for digital audio

Digital audio components rely on clock timing to organize the flow of data. The C18 gives compatible gear a dedicated 10MHz reference clock, helping reduce timing instability in systems built around external clock input. Its phase noise is rated at -110dBc at 1Hz typical, giving connected equipment a cleaner timing reference to work from.

SC-cut OCXO core

At the center of the C18 is an ultra-low-noise oven-controlled crystal oscillator, or OCXO. An OCXO keeps the quartz crystal at a constant temperature, which helps reduce frequency shifts caused by changes in the room around it. The SC-cut crystal is customized for this model and designed for low jitter, low noise, and stable 10MHz output.

Independent output drive module

The C18 uses Gustard’s GDRV-P1 independent drive output module to preserve clock performance as the signal leaves the oscillator. The OCXO alone is not intended to drive multiple downstream devices directly, so the dedicated driver helps maintain low phase noise while distributing the signal. It provides both sine wave and square wave outputs, making it easier to connect different types of compatible equipment.

Four clock outputs

The rear panel includes two sine wave outputs and two square wave outputs. This gives you a practical way to clock multiple compatible devices from one master clock, instead of relying on a single direct connection that may strain the oscillator or limit how your system is arranged.

Linear power supply

The C18 uses a built-in linear power supply with an audio-dedicated toroidal transformer. Clean power matters in a clock generator because ripple, noise, and drift can affect the stability of the signal. The internal power design is built to support the oscillator and output stages without relying on an external supply.

Discrete voltage regulation

Discrete voltage regulation gives the C18 low ripple, low temperature drift, and fast response speed. Multi-channel hierarchical voltage stabilization also helps reduce crosstalk between internal circuits, giving the clock core and drive circuitry a cleaner electrical foundation.

Compatible with 10MHz clock-ready gear

The C18 is designed for use with devices that accept 10MHz external clock signals, including Gustard products such as the U16, S16, and X26 Pro. It can also be used with other compatible digital audio components that support 10MHz clock input. 

Product highlights

• 10MHz high-precision master clock
  
• Ultra-low-noise SC-cut OCXO core
  
• Phase noise rated at -110dBc at 1Hz typical
  
• Two sine wave outputs
  
• Two square wave outputs
  
• Independent GDRV-P1 drive output module
  
• Built-in linear power supply
  
• Audio-dedicated toroidal transformer
  
• Discrete component voltage regulation
  
• Compatible with devices that accept 10MHz clock input

Specs

• Model: C18 constant temper clock
  
• Output frequency: 10MHz
  
• Frequency accuracy: < ±300ppb
  
• Frequency stability: < ±50ppb
  
• Output amplitude: ≥7dBm at 50Ω
  
• Output waveform: Sine wave and square wave
  
• Output impedance: 50Ω
  
• Phase noise at 1Hz typical: -110dBc
  
• Short-term stability, Allan deviation: 8E-13
  
• Power input: AC 115V/230V, 50/60Hz
  
• Power consumption: <15W
  
• Dimensions: 8.66 in wide × 1.97 in high × 6.69 in deep (220 mm × 50 mm × 170 mm), depth without protrusions
  
• Package size: 11.22 in wide × 3.35 in high × 10.63 in deep (285 mm × 85 mm × 270 mm)
  
• Weight: 5.51 lb (2.5 kg), including packaging

What’s included

• Gustard C18 10MHz master clock
  
• C2 clock cable sold separately