Original price was: US$369.US$299Current price is: US$299.
- Mix & Match HRK 500 Products!
| 500 Units | 2 | 4 | 6+ |
| Discount | -10% | -15% | -20% |
- Free Shipping for Orders $299+
- Handmade in HRK Workshop
- Fully Assembled and Tested
- Express Delivery to Europe │ USA │ UK │ Canada
- Inspired by Famous Valve Passive EQ
- Adds Harmonics and analog warmth
- enhances the sound stage and content separation
- perfect for tracking and stereo bus processing
- Intuitive dial-Until-You-Like operation
- Discrete Germanium Transistors Class-A OPAMP
- Additional Passive Transformer Driven By Germanium Circuit
- Two Bands Shelf EQ Operation
- Separate Control for Boost and Cut
- 3 Frequency Settings for HF Band
- 3 Frequency Settings for LF Band
- Coupled with Custom HRK Active Transformer
- On-Board Voltage 500 Rack PSU Filters
- Soft-Start Circuit - Compability with All 500 Racks
- Direct Sale - Save on Distributors Fee!
Stereo Buss Operation
- Our improved production process ensures stereo matching between units
- If you purchase two units in one order, both units are matched for stereo operation, bus processing and mastering.
Germanium Transistors and Passive Audio Transformers
Germanium transistors, when paired with passive audio transformers, produce distinctive harmonic characteristics that are often perceived as sonically pleasing. This effect arises due to the inherent non-linearities in the germanium transistor’s conduction properties, which lead to a smooth, asymmetric clipping of audio signals.
As a result, the transistor amplifies the signal in a way that enriches the sound with even-order harmonics, contributing to a warmer, more “analog” tone. Additionally, when driving a passive audio transformer, these harmonics interact with the transformer’s magnetic saturation and impedance characteristics, further enhancing the overall sound quality.
This combination of germanium transistors and passive transformers effectively adds depth and character to the audio, making it particularly sought after in high-fidelity and vintage audio equipment designs.
The unique feature of Passive Equalizer is the ability to Cut and Boost at the same time.
The EQ550G can create sophisticated EQ curves which cannot be achieved by the active shelf equalizers.
The ability to select three different frequencies independently for Cut and Boost provides countless possibilities in creating custom EQ curves.
The plots below show a few examples of such EQ curves.
Like any other equalizer, the EQ550G can be used to cut or boost the shelf frequencies.
The plots below show the maximum cut and boost for each band and frequency settings.
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.
| EQ550P Specification | ||
| Input Type / Input Impedance | Balanced Electronic | 20k |
| Output Type / Output Impedance | Balanced HRK Active Transformer | Less than 10R |
| Initial Gain | 0dB | All controls set to flat response |
| Max Output Level | +25dBu@1%THD | Balanced Signal |
| Power Consumption | 60mA max. | |
| Format | API 500 Format | |
| Phase Reverse | No | 0 deg. |
| Static Noise | -95dBu@10Hz-22kHz | All controls set to flat response |
| Germanium Transistors | NOS High-Quality, Selected Components |
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
- Our improved production process ensures stereo matching between units
- If you purchase two units in one order, both units are matched for stereo operation, bus processing and mastering.
- Spcial stereo coupling link cable is supplied with every pair of 500 Compressors
All Items are dispatched from Poland in the European Union within 1-3 working days.
| Country / Region | Shipping Cost | Customs Fee | VAT |
| 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 Charge | HMRC 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 Office | No 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. |
| Russia, Belarus – NOT AVAILABLE | NOT AVAILABLE | NOT AVAILABLE | NOT AVAILABLE |
| Worldwide Destination Delivery Time: 3-14 Days | – 29.99USD | Refer 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
If the item is damaged during transport, we will do our best to help you and provide a replacement product.
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