Dan D’Agostino Relentless Epic 1600 Monoblock Amplifier

Staggering Power

After setting the measure for amplifier excellence, the Relentless Monoblock Amplifier underwent a substantial upgrade combining new circuit sections and components to become the Epic 1600. Just as no audio designer has been more relentless than Dan D’Agostino in the pursuit of perfection, no power amplifier has been designed and built to a higher standard than the flagship of the Relentless family.

The Velvet Hammer

A true balanced design—unlike conventional bridged amplifiers—it uses a single front-end topology, based on current mirror circuitry to derive the symmetrical plus and minus rails. Typical bridged amplifier designs use two front end circuits, making it virtually impossible to achieve perfect symmetry between the plus and minus rail. In the Epic 1600, distortion artifacts that appear on one half of the signal will also appear on the other half and thus cancel each other. This unique circuit configuration allows for awesome power output with strikingly low distortion. New input stage devices deliver a 300% increase in current as compared to the previous devices, extending low- and high-frequency performance, while truly impressive distortion figures result from the use of no global negative feedback. The amplifier’s open-loop linearity eliminates the need for this performance-robbing technique. Gain circuits operate in the current domain, assuring that performance does not fluctuate regardless of the current demand. 

With its 5.5-kilowatt power supply feeding over 100 output devices, the Relentless Epic 1600 Monoblock Amplifier easily delivers 1,600 watts into 8 ohms—and when connected to a 220-volt or greater AC mains outlet ,it doubles its output to 3,200 watts into 4 ohms and 6,400 watts into 2 ohms. This power output is maintained with the same musical composure at full power as it is at 1 watt. 

Perfect Balance and Absolute Fidelity

Crucial to the new circuit are the bipolar transistors powering the front end of the amplifier. Activating the 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 circuit topology and the unique copper/aluminum heatsinks, thermal issues become irrelevant. The new bias scheme ensures bias consistency, preventing excessive temperatures even under the greatest demand. Additional regulation circuitry prevents any AC power anomalies from upsetting the amplifier’s input circuitry. The core of the power supply is a 5.5 KVA linear transformer that uses multiple sections running in concert, potted and encased in a metal shield. This design reduces transformer noise to nearly zero and protects the audio circuitry from the transformer’s magnetic field. The transformer feeds a custom-designed rectifier circuit and a600,000-microfarad/100-volt capacitor bank. 

A custom-made Delrin brace mechanically grounds each capacitor to eliminate vibration. A slow-start circuit activates the power supply in stages, preventing capacitive inrush tripping household circuit breakers. 

Ultimate Control for Any Loudspeaker

A critical element of any amplifier output topology is the driver section. In the Epic 1600, the driver transistor has been upgraded to a device that handles 33% more power per device. Doubling the driver transistor count minimizes demand on each individual device and lowers overall amplifier output impedance without resorting to global negative feedback. Individual transistors are used for the positive and negative signal elements, nearly doubling the current drive necessary to maximize the enhanced output stage that follows. D’Agostino’s exclusive Super Rail concept makes maximum use of the incredible resources of this power supply. Super Rail employs higher voltage rails in the sections prior to the output stage, effectively “turbocharging” the amplifier. This voltage boost allows the musical signal to exploit the full capability of the output voltage rails. Extending the musical signal swing closer to the output rails maximizes the performance of the output circuitry design, improving dynamics, lowering distortion, and tightening the amplifier’s 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 112 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. 

Strikingly Elegant

The power meter of the Epic 1600 measures more than eight inches in diameter. Range and response automatically adjust to the level of the incoming signal, making it easy to read no matter how quiet or loud the musical passage. 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 Epic 1600 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 Epic 1600 offers a single XLR balanced input, while speaker cables connect using massive custom-made binding posts made from gold-plated brass. Using the same chassis as the original Relentless Monoblock Amplifier allows upgrades to Relentless Epic 1600 level.