TRUE BLUE 520 Precision Mic Preamp

The CL-520 Microphone Preamplifier / Instrument DI is engineered to deliver stunning musical accuracy, practical and innovative features, outstanding value, and long-term reliability. Every element of its design has been refined through extensive critical listening evaluations and comprehensive user feedback.

The CL-520 features an updated TRUE Systems preamplifier core design, providing ultra-high-resolution musicality and optimized performance with condenser microphones, dynamic microphones, ribbon microphones, and self-powered tube microphones. The original TRUE Systems preamplifier core has been trusted for over two decades in studio, live sound, post-production, and educational environments - supporting virtually every genre of voice and music production.

A unique illuminated Cloud Touch-ControlTM User Interface replaces conventional pushbutton and toggle switches. This advanced interface enables microprocessor-controlled, high-reliability telecom relays for signal and function switching, resulting in significantly shorter signal paths and reduced sensitivity to electromagnetic interference (EMI). The illuminated controls also enhance visibility of preamp status from a distance or in low-light environments.

To enhance operational safety, the CL-520 includes a Blink-Delay feature that helps prevent unintended activation or deactivation of Phantom Power and High-Gain modes.
When either function is selected, its status indicator briefly blinks as a visual warning before activation is engaged after a short delay.

The DI IN and THRU jacks function as a signal split for simplified system integration. The DI IN routes the instrument signal directly to the preamp core, while the THRU jack passes the signal to an amplifier, additional DI, or 500-series module without interruption.

The continuously variable High-Pass Filter (HPF) provides precise low-frequency attenuation across a range of 25 Hz to 420 Hz. This control allows fine adjustment to compensate for microphone proximity effect and is highly effective in reducing low-mid frequency buildup or “mud” in vocals, bass instruments, and other sources.

When the HPF is disengaged, the low-frequency response extends down to 6 Hz, ensuring full bandwidth performance.

◆ APITM 500 Series Module Format
• Compatible with standard API 500 series racks and power supplies.

◆ Fully Balanced Topology - Designed for superior noise rejection and signal integrity:
• Exceptional immunity to ground noise and ground loops
• High resistance to external EMI and interference from adjacent modules or power
supplies
• Ultra-low distortion performance, no capacitors in the signal path (Dyn/Rib mode)

◆ Rail-to-Rail Circuit Design - Optimized for maximum headroom and dynamic range:
• Increased internal operating headroom
• High maximum input level without pad (up to +21 dBu)
• Elevated output level capability without transformer coupling or excessive current
draw

◆ 0.1% Precision Resistors - Ensuring consistent, accurate performance:
• Outstanding common-mode rejection and output signal balance
• Excellent unit-to-unit sonic consistency

◆ FET-Based DI IN and THRU Jacks - Designed for flexible integration:
• Simple connection to amplifiers for simultaneous DI and mic’d tracking or live sound
• Easy routing to additional DI units or effects processors for parallel signal paths

◆ Continuous Detented Gain Control - Precise and repeatable gain staging:
• Detented control for accurate resettability
• Dual gain ranges for optimized control
• Up to 76 dB of total available gain

◆ Cloud Touch-ControlTM User Interface - Advanced reliable control architecture:
• Illuminated controls and status indicators
• Microprocessor-controlled, high-reliability signal and function relays
• Blink-Delay to protect against accidental phantom power or gain switching

◆ High-Pass Filter (HPF)
• Continuous, detented adjustment from 25 Hz to 420 Hz
• Precise low-frequency management

◆ 4-Level Signal Metering
• -20dBu (signal present), +4dBu, +14dBu and +24dBu (OL)

Gain, MIC in: 

+6.5 to +60 dB, +16 touch pad OFF

+22 to +76 dB, +16 touch pad ON

Frequency Response: @ 40dB gain, +26dBu out

-3dB BW = 6Hz to 630kHz

Flatness = +/- 0.25dB 10Hz to 250 kHz

Maximum Output Level: @ 40dB gain

+28 dBu (THD+N =0.0004%)

Maximum Input Level (MIC): @ min gain setting

+21 dBu, 60dB range

+3 dBu, 76 dB range

Input Impedance (MIC): 

5.5kOhm, 48V touch pad ON

10kOhm, 48V touch pad OFF (RIB/DYN mode)

High Pass Filter (HPF): 

25Hz to 420 Hz, 6dB/octave, HPF touch pad ON 6Hz, HPF touch pad OFF

CMRR: @ 40dB gain, +26dBu out

92dB, 30Hz to 20kHz, +10dBu CMV in

Output Balance: @ 40db gain, +26dBu out

80dB , @1kHz

Common Mode Output Offset: @ max gain

40mVDC

Differential Output Offset: @ max gain

5mVDC

Phase Shift: @ +26dBu

2.5deg @ 30Hz to 20kHz, 40dB gain

2.5deg @ 30Hz, 3.3deg @ 20kHz, 60dB gain

THD +N: @ 40dB gain, +26dBu out

0.00036% @ 1kHZ, 20Hz to 20kHz (note 1)

THD: @ 40dB gain, +26dBu out

0.0002% @ 1kHZ (note 1)

Slew Rate: 54V/uS

Intermodulation Distortion:

@ 40dB gain, +20dBu out

0.0005% MOD (u1-u9) (notes 1, 2 )

0.001% DIM 30 (notes 1,3)

NOISE: 

-133dB unwtd 20 to 20kHz, Rs=0

-135dB A wtd, Rs=0

Gain, DI in:

-9 to +43 dB, +16 touch pad OFF

+7.5 to +60 dB, +16 touch pad ON

Maximum Input Level (DI):

@ 20dB gain, +26dBu out

+6 dBu in, THD+N = 0.0007%

Input Impedance (DI): 1 Mohm

Power Consumption: +26dBu out

+16VDC @ 80 mA, -16VDC @ 55 mA,10K ohm load

+16V @ 90 mA, -16V @ 65 mA,1K ohm load

NOTES:

1) Measured value is at or near the residual accuracy limits of Audio Precision APX555-B test system.

2) Similar measurement to SMPTE/DIN 4:1 7kHz/50Hz, but with more detail.

3) Measures high frequency linearity, stability and "edginess" related to transient response.

* Typical performance specifications, subject to change without notice

Shipping

• Cost: Free standard shipping on all orders.
• Processing: 1–2 business days (excluding weekends/holidays).
• Transit: 3–5 business days via FedEx, UPS, or USPS.
• International: Customers are responsible for all customs, duties, and taxes.

Returns

• Policy: 30-day return window for unused items in original packaging (14 days for EU orders).
• Process: Contact support@cloudmicrophones.com for a free return shipping label.
• Fees: No restocking fees on approved returns.
• Refunds: Processed within 10 business days after inspection.