Dan D'Agostino Relentless 800 Monoblock Amplifier

The Relentless 800 features enhanced power supply, input, driver and output stages. It offers lower power output than its bigger brother, yet delivers virtually unlimited power and dynamic contrasts. Even at low volume levels, it produces nuanced and musical sound.

Power to spare: The core of the Relentless Amplifiers’ power supply contains a shielded transformer with multiple winding sections. It produces nearly zero noise and shields the audio circuitry from the transformer's magnetic field. Each capacitor is also securely grounded with a special holder, isolating it from any vibrations.
With its nearly four-kilowatt transformer and 400,000 F capacitance power supply feeding 84 output devices, the Relentless 800 easily delivers 800 watts into 8 ohms—and when connected to a 220-volt outlet, doubles its output to 1,600 watts into 4 ohms and 3,200 watts into 2 ohms.

The Design: The Relentless 800 employs an all-new, fully complementary design based around a precision input stage that maintains an essentially perfect balance between the positive and negative components of the signal. Any distortion artifacts that appear on one half of the signal will also appear on the other half, and thus cancel each other. Gain circuits operate in the current domain, assuring the amplifiers’ performance does not fluctuate regardless of the speaker demand.

In the Relentless 800 amplifiers, new input stage devices deliver a 300% increase in current as compared to the previous devices. These wider bandwidth, higher power components extend low and high frequency performance with reduced distortion in both frequency extremes. Global negative feedback is not employed, nor is it required as the amplifiers’ open-loop linearity eliminates the need for this performance-robbing technique.

Activating the reimagined driver stage is a new bias stability circuit providing a nearly 50% increase in operating bias. Increasing Class A operation directly correlates to better sound quality. With this new circuit topology and the unique Copper/Aluminum heatsinks, thermal issues are irrelevant in the Relentless 800 amplifier. The new scheme ensures bias consistency, preventing excessive temperatures even under the greatest demand.

In the new Relentless 800 amplifiers, the driver transistor has been upgraded to a new device that handles 33% more power per device. Additionally, the driver transistor count has doubled thus minimizing demand on each individual device and lowering overall amplifier output impedance without resorting to global negative feedback. Individual transistors are used for the positive and negative signal elements in an inter-digitated complementary arrangement. This nearly doubles the current drive necessary to maximize the enhanced output stage that follows.

Super Rail employs higher voltage rails in the sections prior to the output stage, effectively “turbocharging” the amplifier and exploiting the full capability of the output voltage rails—which improves dynamics, lowers distortion, and tightens the amplifiers’ electrical grip on the speaker.

The output stage features the same new transistor as in the driver section for sonic and technical consistency. Individual complementary pairs undergo our transistor matching protocol to ensure that gain linearity is virtually identical from 50mA to 5A. Additionally, every one of the 84 output transistors used is measured and only devices that match the required performance specifications are included in the production of Relentless 800 amplifiers. The high-output transistors used in the Relentless 800 are among the fastest available. These high-powered transistors mount with two stainless steel fasteners—a rarity among flat-package transistors—for maximum thermal transfer to the copper heat sinks. A capacitor/resistor network connected to the base of each transistor guarantees stability even at high frequencies and with low-impedance speakers. As with all D'Agostino models, the Relentless 800 amplifiers feature discrete, direct-coupled balanced circuitry - the most accurate circuit platform possible.

Elegantly Functional: The Relentless 800 Amplifier’s unique heat sink combines copper and aluminum in a thermal engine that wicks away heat from the connected devices. The elaborate elliptical design expands on the venturi heat sink first explored in the Momentum series and makes certain that the Relentless amplifiers run safely and reliably even when delivering its full rated power. Thermal, short circuit, and DC protection are included in a non-invasive but comprehensive defense against any external system faults.
The entire chassis of the Relentless 800 amplifiers are machined from solid aluminum, for superior shielding, thermal stability, and vibration damping. High-precision milling allows the entire chassis to fit together solidly with no visible fasteners.

Frequency Response 20 Hz to 20 kHz, ±0.1 dB

Signal-to-Noise Ratio 113 dB, unweighted, ref. to full power output / 80 dB, A weighted

Finish Silver / Black / Custom finishes

Total Harmonic Distortion 800 watts @ 8Ω 0.1% @ 1 kHz

Input Impedance 120 MΩ

Output Power 800 watts @ 8Ω / 1,600 watts @ 4Ω / 3,200 watts @ 2Ω

Inputs 1 balanced XLR

Outputs 1 pr Speaker Binding Post

Dimensions 21.6 x 10.4 x 26.0 in / 54.9 x 26.4 x 66.0 cm

Weight 320 lb / 145 kg

Drawings Relentless 800 full dimensions.PDF (291.73 KB)

Sell Sheet Relentless 800 Monoblock Amplifier Sell Sheet.pdf (472.82 KB)