Dan D’Agostino Relentless 800 Monoblock Amplifier

Might Makes Right

After setting the measure for amplifier excellence with the Relentless Epic 1600 Monoblock Amplifier, the Relentless 800 Monoblock Amplifier brings Relentless sound quality to smaller platform. Employing the same circuit topology as the Epic1600, its power supply, input, driver, and output stages have been engineered to distinguish it from its bigger brother only by lower power output.

Power to Spare

Nuanced and musical at low volume levels, the Relentless 800 delivers the striking dynamic contrasts that bring music to life. The core of the power supply is a transformer using multiple sections running in concert, potted and encased in a metal shield, reducing transformer noise to near zero and protecting the audio circuitry from the transformer’s magnetic field.

The nearly four-kilowatt transformer and 400,000 μF capacitance power supply feed 84 output devices, allowing the Relentless 800 to easily deliver 800 watts into 8 ohms. When connected to a 220-volt outlet, output doubles to 1,600 watts into 4 ohms and 3,200 watts into 2 ohms.

The Design

Fully complementary design based around a precision input stage maintains 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 amplifier’s performance does not fluctuate, regardless of the speaker demand. 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 required, as the amplifier’s open-loop linearity eliminates the need for this performance-robbing technique.

A new bias stability circuit in the driver stage provides 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 become irrelevant, the new scheme ensuring bias consistency, preventing excessive temperatures even under the greatest demand. 

A critical element of any amplifier output topology is the driver section. In the Relentless 800, the driver transistor has been upgraded to handle 33% more power per device. Additionally, the driver transistor count has doubled, 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 a complementary arrangement, nearly doubling the current drive
necessary to maximize the enhanced output stage that follows.

Super Rails

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, improving dynamics, lowering distortion, and tightening the amplifier’s 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 is measured, and only devices that match the required performance specifications are used. The high-output transistors are among the fastest available, and 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.

Elegantly Functional

The amplifier’s unique heat sink combines copper and aluminum that wicks away heat from the connected devices, using an elaborate elliptical design, allowing the amplifier to run safely and reliably even when delivering full rated power. Thermal, short circuit, and DC protection are included in a non-invasive but comprehensive defense against any external system faults. The chassis of the Relentless 800 is 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. The Relentless 800 offers a single XLR balanced input, while speaker cables connect using massive custom-made binding posts made from gold-plated brass.