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ST596 | Analog Harmonics Processor


500 Units 2 4 6+
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ST596 | Analog Harmonics Processor
St596 Analog Hardware Harmonic Processor Hrk Fp

ST596 | The DAW Plugins Killer!


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ST596 – The End of Your Struggle!

Did you try countless DAW plugins to get the “true sound” and “analogue warmth” of the vintage studio preamps or consoles? Have you noted that all plugins sound similar, and if you add more plugins, the result is only less satisfying?

It is not much you can do about it… The DAW plugins are the only emulation of the analogue circuits, and your computer is not capable of calculating the mathematics involved in complex physical processes which happen every nanosecond in the analogue hardware.

Have you tried to patch the signal through the clone of the “vintage” mic preamp or compressor, only to battle with noise, hum, and ground loops for hours?

You won’t win with the laws of physics. Every time you add the gain, the noise floor will rise, and every cable conducts the electric current, which may create the ground loop…

The ST596 is a solution for all the above and many other problems which almost every music producer or studio engineer has encountered.

Learn more about how the ST596 can help you to enjoy your work.

ST596 Demo and Introduction

Analog Modeling Circuitry by Bart Hrk

Bart Hrk designed the Custom Analog Modeling Circuitry, which produces complex harmonic content without the usual problems associated with digital or common hardware saturation.

The typical way of producing the harmonics is to overdrive the signal with analogue hardware. Usually, the gain has to be increased to achieve the desired results, which also raises the noise and hum levels, normally residing below the audible threshold.

Hardware components such as the thermionic valves, transformers, and discrete circuits produce harmonic distortions, and this process can be described by the mathematical equations.

Simplified equations are used by the computer programs, the audio plugins to simulate the properties of the analogue hardware. More advanced plugins use expensive DSP cards to offload the main CPU and deliver more realistic results.

Bart Hrk Analog Modeling Circuitry used in the ST596 does the math of generating harmonics in the real-time analogue domain. No digital approximation, no latency, no CPU bottleneck!

The ST596 does not increase the gain of the processed signal keeping the noise as low as possible. It just adds the harmonics to the source signal.

Although the processed signal can be perceived as louder due to the higher harmonics content, the peak level of the signal remains almost the same.

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Analog Tape Emulator

The ST596 Analog Tape Emulator mimics the frequency responce and produce the harmonics similar to the tape recorder.

Tape Emulator is an addition to the main harmonics block of the ST596 and can be used to add the final touch to the processed signal.

The level of the tape saturation level can be controlled by the level of the signals sent from the WET and DRY knobs. Tape harmonics can be blended with the Tape Mix knob.

The LF Resonant circuit can be engaged with the onboard jumper, which is helpful for vocals and the lead instruments.

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Intuitive Control and Workflow

The ST596 is easy to use. The number of knobs and switches is limited to a minimum to provide a hassle-free operation.

The Drive knob controls the amount of harmonics produced by the Analog Modeling circuit. Only the harmonics are added to the source signal.

The Wet knob sets the level of harmonics added to the source signal.

The Dry knob controls the level of the source signal and the total output level when the ST596 is engaged.

The Tape Mix knob allows the blending between the signal processed by the Tape Analog Emulator and the signal from the previous stages.

The HFC switch cuts off the high frequencies to remove the air harmonics content. This feature helps with vocals and other HF-rich signals. It can also be used in a creative way.

The LFS switch blocks the LF content passed to the Analog Modeling circuit, preventing the lows from being overdriven. This feature helps with LF-rich signals such as drums, bass guitar, bass synths, and bass tracks.

The Tape-In switch engages the Tape Emulator circuit. The Process switch works as the bypass switch.

Simplified Signal Flow Diagram

St596 Analog Harmonics Processor Signal Flow Diagram

Stereo Buss Operation

Stereo Spk

HRK Active Transformer

Hrk Active Transformer

Bart Hrk has developed a proprietary design for an Active Transformer, aimed at addressing the limitations of traditional passive transformers.

Traditional passive transformers are known to be vulnerable to electromagnetic interference, such as 50/60Hz hum and HF RF smog. Additionally, their frequency response is contingent upon load and source impedance, which adversely affects the overall performance of analog studio equipment.

The HRK Active Transformer is a game changer that not only resolves the issues associated with passive transformers but also retains and amplifies the desired characteristics of the transformer output stage. This includes the enrichment of harmonic content and the enhancement of tonal response.

What sets the HRK Active Transformer apart is its ability to deliver the rich, beloved sound that audio enthusiasts seek, including the harmonic content and tonal response, while simultaneously eliminating the drawbacks of passive transformers.

Furthermore, the Active Transformer introduces a delicate “Air” effect and boasts an extended low-frequency (LF) performance, adding depth and clarity to the sound.

Another remarkable feature of the Active Transformer is its dynamic saturation, which is dependent on the output level. As the output signal level increases, the Active Transformer exhibits greater saturation, reminiscent of the warm and rich sound produced by classic studio equipment.

In summary, the HRK Active Transformer is an innovative solution that offers superior sound quality, eliminates electromagnetic interference, and enhances harmonic content and tonal response. It is an invaluable asset for professionals and audiophiles seeking to elevate their audio experience.

ST596 Demo Videos

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User Manual:

Please read the User Manual before the use of the ST596.

ST596 User Manual
ST596 Recall Sheet
ALL HRK Products Are Brand New - Assembled and Fully Tested

All HRK Products are tested with the industry’s best audio measuring equipment – The Audio Precision

Audio Precision is an industry leader in providing high-quality audio testing equipment. They are renowned for their test systems’ precision, reliability, and versatility.

When testing studio audio devices, Audio Precision’s equipment can assess parameters like frequency response, harmonic distortion, intermodulation distortion, phase response, signal-to-noise ratio, and cross talk. In-depth and accurate testing allows the identification of even the smallest issues in audio quality, enabling corrections and improvements that can significantly elevate the overall product quality.

In conclusion, using Audio Precision test equipment is an excellent way to ensure that all HRK products are performing at their best, meeting the standards required for the Professional Studio Applications.


Stereo Buss Operation

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

Country / RegionShipping CostCustoms FeeVAT
All 27 European Union Countries – Delivery Time: 2-7 Days

– 14.99USD for orders below 299USD

– FREE shipping for orders over 299USD

NO Customs Fees– Yes, for personal orders- Not charged with the EU VAT number
United Kingdom – Delivery Time: 3-7 Days

– 14.99USD for orders below 299USD

– FREE shipping for orders over 299USD

No VAT ChargeHMRC collects the VAT or additional Fees if applicable.
USA, Canada – Delivery Time: 5-10 Days

– 14.99USD for orders below 299USD

– FREE shipping for orders over 299USD

NO Customs Fees for orders up to 800USD – charged by the USA Customs OfficeNo VAT charge.
Australia, Japan, South Korea –  Delivery Time: 5-14 Days

– 19.99USD for orders below 299USD

– FREE shipping for orders over 299USD

There is no info available – refer to local regulations.No VAT charge.
Switzerland Delivery Time: 3-7 Days

– 14.99USD for orders below 299USD

– FREE shipping for orders over 299USD

There is no info available – refer to local regulations.No VAT charge.
Norway Delivery Time: 3-7 Days

– 14.99USD for orders below 299USD

– FREE shipping for orders over 299USD

There is no info available – refer to local regulations.No VAT charge.
Worldwide Destination Delivery Time: 3-14 Days– 29.99USDRefer to local regulations.No VAT charge.

EU Customers

EU Customers will not pay any extra customs fees.

Business customers with a valid EU VAT number will not have to pay VAT tax.

Please enter your EU VAT Number at checkout and the VAT will be deducted from the Total Payment. The VAT number is automatically checked in the VIES database.

For personal orders from the EU, VAT will be added at checkout.

UK Custmers

We ship directly to United Kingdom.

UK VAT tax is collected by HRMC

Non-EU Customers

Customers from outside the EU purchase 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 a custom invoice will be issued.

USA and Canada

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

We ship directly to the USA and Canada

Payment Options:

You can pay for your order with any Credit Card or Apple Pay!

PayPal – We do not use PayPal as a payment method.

7 Days Return Policy

Our return policy is a part of the general Terms & Conditions, which you must acknowledge at the checkout. We stand by fair rules and a win-win approach.
We understand that our customers may wish to return the product and we provide such an option.
However, because we are a small company, we can’t afford to run a grade B outlet shop like big distributors and provide a 30 day return period. We can’t also scrap every returned unit.
We can charge our customers more to offset the cost of the returns, and 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. If you wish to return the item, we will accept the return request, provided that the item is not damaged.

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