ST596 | Studio Analog Harmonics Processor and Tape Emulator - Similar to SAT500 - Matched Pair

U.S. Import & Tariff Notice for American Buyers

No Section 232 Tariffs Apply / Composite Front Panel

• Zero Aluminum / Composite Front Panel: Please note that the front panel of this API 500-series module is made entirely from a high-grade composite material—it contains no aluminum. As such, this item does not contain aluminum subject to Section 232 tariffs or additional import surcharges when entering the United States from Europe.
• Open-Frame Construction (No Metal Chassis): This unit features an open-frame design consisting solely of the PCB and internal components, without any external steel or aluminum enclosure. It contains no bulk metals that fall under U.S. metal tariff regulations.
• Private Sale Declaration: This item is being sold by a private individual for personal/used gear resale.

U.S. buyers can purchase with confidence knowing this module is exempt from steel/aluminum tariff classifications.

This is listing is for the ST596 Matched Pair — you get 2 units

• ST596 | Analog Harmonics Processor and Tape Emulator
• Adds Harmonics and Saturation
• Analog Modeling Discrete Circuitry
• Germanium and Silicon Transistors Tape Emulator
• Custom Coupled Inductors – Tape Head Emulation
• Independent DRY and WET Controls
• Tape Mix Control
• High Frequencies Cut Filter
• Low Frequencies Safe Feature
• Custom HRK Active Transformer Output
• Class A Discrete Transformer Driver
• High-Quality ALPS Potentiometers
• Studio-Grade Low Noise Opamps
• Balanced Input
• Compatible with API 500 Format
• Direct Sale – Save on Distributors Fee!
• Fully Assembled and Tested

The ST596 is an Analog Harmonics Processor dedicated to professional music producers and studio engineers.

The ST596 adds harmonics and saturation to any music material, providing the full control of the amount of the harmonics and the Dry and Wet signal level.

The ST596 is based on the Custom HRK Analog Modeling circuitry built with discrete components, which produces a complex spectrum of harmonics.

The ST596 does not significantly change the overall peak level of the processed waveforms, nor distort the source signal, like in the common saturation studio hardware.

The ST596 is easy to use, and intuitive controls make the tracking, reaping or mastering a quick and satisfying job.

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 to calculate 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 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 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.

More demo videos on YouTube.

The Analog Modeling Circuitry

The ST596 Analog Harmonics Processor uses the custom-designed Analog Modeling discrete circuitry which produces the complex harmonic content without the usual problems associated with digital or hardware saturation.

The common 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 raise the noise and hum levels, normally residing below the audible threshold.

Hardware components such as the thermionic valves, transformers and discrete circuits produce the 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 the analogue hardware. More advanced plugins use expensive DSP cards to offload the main CPU and deliver more realistic results.

The term Operational Amplifier, which is the most common electronic component today, has its roots in the long-forgotten past when the mathematical calculations were done by the analogue computers built with amplifiers capable of conducting mathematical operations. Hence the name.

The 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.

The Analog Tape Emulator

The ST596 Analog Tape Emulator circuitry is based on the discrete germanium and silicon transistors, including FET transistor, and delivers the subtle final touch to the processed signal.

Custom coupled inductors act like the write and read tape heads, adding harmonics of the tape recorder.

The level of the tape saturation can be controlled by the level of the signals sent from the WET and DRY knob.

The tape harmonics can be blended with the Tape Mix knob.

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

Intuitive Control and Workflow

The ST596 is easy to use. The number of knobs and switches are limited to a minimum to provide the 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 be used also in a creative way.

The LFS switch blocks the LF content passed to 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.

Tape-In switch engages the Tape Emulator circuit.

The Process switch works as the bypass switch.

Presenting a rare opportunity to acquire the final remaining API 500 series modules from the legacy HRK Shop. As the original workshop has now closed its doors, these highly coveted units represent the absolute last of their kind. Once this exclusive inventory is depleted, they will never be manufactured again. To mark this final release, we are offering these pieces at special legacy pricing. Depending on the specific model, certain units are fully completed, meticulously packed, and ready for immediate worldwide dispatch within 48 hours.

Other select modules await their final bespoke finishing—a streamlined but precise process involving the fitting of front panels and precision control knobs. Please review the detailed specifications below to confirm whether your chosen module is ready to ship or pending its final assembly touches.

Every module offered here is pristine, unplayed, and strictly factory-new, originating directly from the authentic HRK Shop's final production run. This is a fleeting chance to integrate a piece of original boutique audio engineering into your workflow. Once these final units find their studios, this opportunity will be gone forever.

Shipping to USA / CANADA / EUROPE