© 2025 HRK Shop
Original price was: CZK8 734.71. CZK7 640.13Current price is: CZK7 640.13.
| 500 Units | 2 | 4 | 6+ |
| Discount | -10% | -15% | -20% |
The EQ550P is a Passive Germanium Transistors based Two Band Shelf Equaliser inspired by the famous Pultec design.
Each Band has a separate Boost and Cut Control which allows creating the sophisticated EQ curves.
Each Boost or Cut control has three different and independent frequency settings which give a total of 9 setting combinations per Band.
The Passive filter section changes the EQ curve by attenuating the signal. The Germanium Discrete OPAMP gain stage, which drives an additional Passive Transformer, restores the signal to the nominal level, adding the combination of harmonics and transients.
The EQ550P is very musical and easy to use. It can process any music material, instruments, vocals or recordings, producing outstanding results.
The Germanium Discrete Transistors Hybrid circuit with Passive Transformer is the result of years of development and refining process. It produces Vintage 60’s-Like Harmonics and upscaling the tone while maintaining the noise on an extremely low level.
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.Standard Cut and Boost 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.
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.
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.
| 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 |
