CP523V | Valve Optocompressor – OUTLET SALE

$319.00 $189.00 ex. VAT


All units are in perfect working order, fully assembled and tested. Some units may have signs of use such as minor traces on the front panel.

  • Mix and Match HRK 500 Products!

Out of stock

Categories: ,



  • Fully Featured Valve Opto-Compressor
  • Discrete Tube Class A Gain Stage
  • Side-Chain High Pass Filter
  • Threshold from -30dB to +10dB
  • Ratio from 1:1 to Limiter
  • Slow / Fast Attack Switch
  • Recovery from 50mS to 2S
  • +20dB Gain Make-Up
  • Stereo Coupling Option
  • 10 LED Gain Reduction Meter
  • Output Coupled with Custom HRK Transformer
  • J Electronics ECC83 Dual Triode Tube
  • On-Board Voltage 500 Rack PSU Filters
  • Direct Sale – Save on Distributors Fee!

The CP523V is a Tube based fully featured optocompressor with a Class A gain make-up stage.

The CP523V has separate controls for Threshold, compress Ratio, Recovery time and Output Gain.

The Attack time can be set with the switch to Fast or Slow. The Slow Attack is perfect for adding the edge to the drums or bass recording.

The Sidechain High Pass Filter removes the low-frequency content from the processing greatly enhancing the capabilities of the CP523V for tracking and mastering.

The CP523V is very musical and easy to use. It can process any music material, instruments, vocal or recordings, delivering amazing results.

The Valve – Discrete Transistors Hybrid circuit is the result of a long development process. It produces rich Tube harmonics and tone while maintaining the noise on the extremely low level.

Create Amazing Results Easily!

The CP523V is easy to use even for engineers with less experience with dynamic processors.

Optocompressors are very versatile and produce smooth compression results. Any music material will benefit from the magic touch added by the CP523V.

The sidechain controls are simple and powerful providing the necessary tools for many demanding studio applications.

Add Harmonics to your Recordings or Tracks

The CP523V is suitable for recording as a part of the signal path. It will control the dynamics of the signal from the microphone while enhancing the details and structure of the vocal or the instruments.

The CP523V can be used for tracking or mastering. Two units can be paired in stereo mode. The Slow Attack mode and the side-chain High Pass Filter can be used very creative way in mastering applications.

Stereo Mode

A pair of CP523V will work in a stereo mode. Two units can be coupled with a special link cable added for free if two CP523V units are purchased. If you purchasing second CP523V unit simply add the request for the link cable in the information section during the checkout. The cable will be added to your order for free.

The matched CP523V pair is also available as the separate item on this website.

More information about how to use CP523V in stereo mode can be found in the User Manual.

Coupled with Custom HRK Transformers

The Output of the CP523V is coupled with specially designed custom HRK Transformers. Because of limited space in the 500 modules, HRK Custom Transformers became smaller, maintaining no-compromise performance.

All HRK transformers provide the sweet-spot sonic characteristic with pristine detail reproduction. The goal of the design process was to create the transformer which will deliver a balance between the transparency and colouration typical for transformers.

Discrete Transistor Class A Output Transformer Driver

The output transformer is powered by Class A, No-Feedback, DC-Coupled Discrete Driver.

Acoustic Guitar Demo Video

Acoustic Guitar Demo Track

CP523V set to moderate compression settings. Slow Attack, Medium Recovery, HPF- IN

      Acoustic Guitar - Dry
      Acoustic Guitar - CP523V

Female Vocal Demo Video

Female Vocal Demo Track

CP523V set to moderate compression settings. Slow Attack, Medium recovery, HPF- IN

      Female Vocal - Dry
      Female Vocal - CP523V

Drums Demo Video

CP523V set to moderate compression settings. Slow Attack, Fast Recovery, HPF- IN

      Drums - Dry
      Drums - CP523V


CP523V User Manual – Coming Soon…

Item Condition

Brand New, Assembled and Tested.

Every single HRK product is carefully tested with Audio Precision test equipment before the shipping to ensure hassle-free operation.

Payment & Shipping


All Items are dispatched from the European Union within 1-3 working days.

We offer fast worldwide UPS shipping with tracking.

FREE delivery is available for orders over the 249USD to EU, USA and Canada.

FREE delivery is available for orders over the 299USD to Australia, New Zeland, Japan and other destinations.

Please check the shipping cost during the checkout.

Delivery to other WorldWide destinations – 24.99USD

EU Business Customers

All prices exclude the VAT Tax.

If you have the EU VAT number you can purchase the products available in the Bart HRK Shop with no VAT Tax.

Please enter your EU VAT Number at the checkout and the VAT will be deducted from the Total Payment.

Non-EU Customers

Customers from outside the EU can purchase the items with no VAT.

Please select the destination country and the VAT will be removed automatically.

If the VAT is not removed, please email customer service via the contact form and custom invoice will be issued.

Orders from the USA below 800USD are customs tax-free.

Payment Options:

You can pay for your order with any Credit Card



Input impedance: 10kOhm

Output impedance: 100R

Phase inverse: none

Gain: 0dB

All HRK Colour Modules are fully compatible with DIYRE Colour Format

All HRK Colour Processor and Preamps fully compatible with DIYRE Colour Format

All HRK 500 products are fully compatible with API 500 Format

You may also like…