— Dan D'Agostino Master Audio Systems introduced the Relentless Epic and Epic 800 Mono Amplifier at the High End Munich Show. Four years after setting the measure for amplifier excellence, the Relentless Mono Amplifier has undergone an upgrade - the Epic. Combining new circuit sections and components, the Relentless Epic Amplifier resets the standard in power amplifier performance. In an active system, the Relentless Epic 800 makes its world premiere paired with the Relentless Preamplifier. Coupling the new Epic circuit topologies to an 800 Watt/8 Ohm power rating, the Relentless Epic 800 extends D'Agostino Reference sound quality to a smaller package.
Every major section of the Relentless Epic Mono Amplifiers- power supply, input, driver, and output stages - have all been enhanced in this advancement. A new power management topology further isolates the power supply from the entirety of the audio circuitry providing extra protection from the noise the massive power transformers can generate.
The Relentless Epic and Epic 800 employ an all-new, fully complementary topology 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 Epic and Epic 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.
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 new circuit topology and the unique Copper/Aluminum heatsinks, thermal issues are irrelevant in the Relentless Epic and Epic 800 amplifiers. 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 amplifiers’ input circuitry.
“With the Relentless Mono Amplifier, we focused on creating an amplifier without any limits”, said company co-founder and chief engineer Dan D’Agostino. D’Agostino continued, “The time since its introduction has allowed us to take the Relentless platform to another level. The original Relentless Mono Amplifier incorporates these changes as the Relentless Epic and we simultaneously developed the Relentless Epic 800 Mono amplifier. The Relentless Epic 800 incorporates the same circuit platform as its bigger brother with a lower power output. Mind you, the Relentless Epic 800 is virtually unlimited when it comes to power delivery and is only outdone by the Relentless Epic itself. I have always found that high powered amplifiers make for the most musical playback at low volume levels while having the capability of delivering the most striking dynamic contrasts no matter how demanding the speaker load may be.”
A critical element of any amplifier output topology is the driver section. In the new Relentless Epic and Epic 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.
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 (Relentless Epic) or 84 (Relentless Epic 800) output transistors used is measured and only devices that match the required performance specifications are included in the production of Relentless Epic and Epic 800 amplifiers. The high-output transistors used in the Relentless Epic and Epic 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 Epic and Epic 800 amplifiers feature discrete, direct-coupled balanced circuitry - the most accurate circuit platform possible.
The Relentless Epic 800 benefits from all the circuit updates employed in the Relentless Epic amplifier but in a smaller package. With its nearly four-kilowatt transformer and 400,000 mF capacitance power supply feeding 84 output devices, the Relentless Epic 800 easily delivers 800 watts into 8 ohms—and when connected to a 220-volt outlet, it doubles its output to 1,600 watts into 4 ohms and 3,200 watts into 2 ohms.
The core of the Relentless Epic Amplifiers’ power supply is a transformer that uses multiple sections running in concert, all potted and encased in a metal shield. This design reduces transformer noise to near zero and protects the audio circuitry from the transformer’s magnetic field. A special holder mechanically grounds each capacitor eliminating vibrations. A slow-start circuit activates the power supply in stages, eliminating concerns about capacitive in-rush tripping household circuit breakers.
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 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 Relentless Epic and Epic 800 Amplifiers’ 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 Epic 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 Epic and Epic 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.
The new Relentless Epic Mono Amplifier uses the same chassis as the original Relentless Amplifier. Every Relentless Amplifier can be upgraded to the Relentless Epic level. All electrical enhancements are included in the upgrade while the original metalwork is retained.
