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$649.00 $549.00 ex. VAT

  • Mix and Match HRK 500 Products!
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Product Description


  • 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 opto compressor 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 – 96k HD Audio

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 – 96k HD Audio

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 – 96k HD Audio

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

      Drums - Dry
      Drums - CP523V


CP523V User Manual – Coming Soon…

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.


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

We offer Fast & Free Worldwide UPS shipping with tracking.

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

Total cart value / Delivery cost:

up to 99USD / Delivery Cost – 19.99USD

99 – 148USD / Delivery Cost – 14.99USD

149 – 248USD / Delivery Cost – 9.99USD

over 249USD – FREE Delivery

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

Total cart value / Delivery cost:

up to 148USD / Delivery Cost – 19.99USD

149 – 298USD / Delivery Cost – 14.99USD

over 299USD – FREE Delivery

Please check the shipping cost during the checkout.

Delivery to other WorldWide destinations – 24.99USD

VAT and Customs Fees

For non-business orders from the EU, the VAT will be added at the checkout.

VAT is removed automatically for orders from outside the EU.

No Custom Fees for EU Customers.

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

EU Business Customers

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.

The VAT number is automatically checked in the VIES database.

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!

Return Policy

Our return policy is a part of the general Terms & Condition which you have to acknowledge at the checkout.

We stand for fair rules and a win-win approach. We understand that our customers may wish to return the product and we do provide such option. However, because we are a small company we can’t afford to run a grade B outlet shop like big distributors and provide the 30 days return period.

We can’t also scrap every returned unit. We could charge our customers more to offset the cost of the returns, this is what major distributors do. Or we can keep our prices low and hope that our customers will appreciate our policy.

This is why we provide the 7 days test period after receiving the package with the ordered items and if you wish to return the item we will accept the return request, providing that the item is not damaged and we can resell the product with the minimal loss for the company.

If the item is damaged during the transport we will do our best to help you and provide the replacement product.


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