Hertz ADC
(Advanced D-Class)

The Herz SP compact amplifier range consists of three high-performance models. There are two four-channel models, the flagship SP4.900 with 160 x 4 W RMS at 4Ω and the SP4.500 with 90 x 4 W RMS at 4Ω, and a mono model SP1.900 boasting 1000 W RMS at 1Ω.

Hertz SP amplifier are the first Hertz amplifier featuring the renewed Hertz ADC (Advanced D-Class) output stage, reaching up to 87% efficiency and delivering an impressive power rating, with an ultra-compact size. 

Being ultra-compact with an impressive power, SP amplifiers are the ideal choice for Motorcycle application and for under-seat in sport cars and behind-seat installations in trucks.


Hertz ADC technology ensures SP amplifiers overtake the usual ultra-compact amplifier performances, delivering an outstanding S/N Ratio and THD specifications, and almost completely eliminating EMI and RFI noise, for peerless sound quality.

This versatility of the four-channel models is perfect to drive high-power (4Ω) front speakers with a bridged (4Ω) subwoofer.

SP amplifiers are fully protected against overheating and DC outputs, immediately switching in protection mode (red LED on) to save your speaker system.

The IP55 certified Aluminum chassis offers maximum protection against humidity and external agents and the absence of an internal cooling fan prevents the accumulation of dirt. SP amplifier’s main board has conformal coating layers to prevent harm caused by internal condensation, a condition that can happen when warm, moist air meets the amp chassis of a lower temperature.

All controls are protected by a removable aluminum panel, to make the SP 4.900 IP55 compliant, preventing humidity reaching the switches.

SP amplifiers feature a built-in sealed power cord, line inputs, and speaker outputs for a bulletproof motorcycle application providing safe power delivery in even the worst weather conditions. The solid power supply harness ensures ultra-stable power and ground connection, preventing any loss of contact caused by vibration. Due to its specific design, SP amplifiers are the ultimate option for Motorcycle, Marine, and Powersports applications.

SP 4.900 features built-in USS (Universal Speakers Simulator), a dynamic load circuit on Hi-Level inputs which initially shows the OEM output channel a load low enough to neutralize OEM speaker outputs muting protection circuit. Once the circuit activates, a higher load is introduced – still low enough to damp Class D outputs, but not low enough to cause current issues or heat dissipation problems.

SP 4.900 offers both remote-in signal detection and DC offset sensing on the speaker inputs for automatic turn on, providing total integration with any vehicle.

The versatile crossover filters and control knob are all located on a single side, to allow an easy calibration when the product is installed.

The filters section includes extremely flexible high-pass and low-pass crossovers, adjustable from 50 Hz to 5 kHz with 12 dB/Oct slope. Together with a bass-boost control (45 Hz, 0÷8 dB), they allow both front channels to be configured for full-range operation, or for use with a subwoofer and related speakers.

The high-pass crossover can also be used to optimize the performance of SPL Show NEO high-efficiency coaxial speakers, the perfect partners for SP amplifiers.