Dan D’Agostino Master Audio Systems has just announced the Relentless Preamplifier, the companion model to the company's 2018-issue flagship Relentless Mono amplifier. Yes, it has taken over three years, but in the relentless pursuit of ever-better performance, there's no such thing as a hard deadline – and also, you'll have needed that time to save up for this particular preamp.
The Relentless Preamplifier's design requires the use of three separate chassis – a dedicated audio chassis for each channel and a separate power supply centered between the two, to keep the power supply feeds as short as possible. These three chassis interlock through special mechanisms in the mounting feet of each chassis, with 30-pin interlocking 20-amp gold plated connectors to eliminate the wiring normally used for these applications (and the associated anomalies that can occur). This distinctive construction also isolates the audio signal completely, both physically and electrically, from the power and digital control sections.
Positioned between the two audio channels, the power supply makes use of extensive electrical and magnetic shielding to keep radiated interference out of critical preamplifier circuits.
Power for the preamplifier stages comes from two 150 VA toroidal transformers – one dedicated to the analogue circuitry and one for the digital and control circuitry. These transformers drive an 8-amp bridge rectifier and 26,400 microfarads of filter capacitance. The two regulators for the analogue stages are scaled-down versions of those used in the Relentless Mono amplifier.
Interestingly, the input stage in each mono preamplifier is the result of a circuitry design experiment that has not been used in any previous D’Agostino preamplifier, until now. The topology starts with an all-new unique discrete differential FET input stage, featuring a voltage input signal capability of an eyebrow-raising 30 volts. With an input impedance of over 1 Mohm, the Relentless Preamplifier’s front end is, says Dan D'Agostino, "immune to source related electrical issues".
A unique circuit developed specifically for this product also promises to maintain a stable bias so that temperature related anomalies are offset, thus avoiding component heating and preserving performance during extended listening.
Featuring only balanced XLR inputs, the Relentless Preamplifier uses proprietary multiple-output current mirrors boasting nearly 30 times the linearity of other designs, plus four-layer circuit boards for superior signal quality (compared to those more commonplace two-layer boards).
Elsewhere, the signal switching relays are hermetically sealed and use gold-plated contacts for maximum signal integrity and the core D’Agostino circuit concepts promise a signal path that is fully complementary, direct coupled, and balanced from input to output to boast a frequency response flat to 120 kHz.
And co-founder of the firm Dan D’Agostino himself is clearly proud of it, saying, “It has been a more than four-decade pursuit and the Relentless Preamplifier is a crowning jewel of my career.”
Visually, the most striking element of the Relentless Preamplifier is the pair of volume controls fronting the two audio chassis. Each is constructed using 14 separate metal components, and since the Relentless Preamplifier is a two source/two zone preamplifier, it can simultaneously control the switching and volume of two sources in two separate rooms or zones.
And we need to mention that Swiss watch-style machined aluminum and copper remote control, operated via touch pad (below).
Finally, the Relentless Preamplifier is the first D’Agostino preamplifier to offer an optional digital streaming module (DSM), offering connectivity for legacy sources, USB functionality, and hi-res streaming capability. The DSM adds SPDIF coaxial, Optical, USB-A, and RJ-45 and wi-fi network inputs. For latency free playback of high-resolution network content, 10/100/1000 Gigabit Ethernet is supported.
Requiring three separate circuit boards, the core element of the module is a pair of DACs configured in differential mode, capable of handling today’s highest resolution sources, including PCM signals up to 32 bit/384 KHz and DSD signals up to DSD256 (11.2MHz) decoded natively.
The Relentless Preamplifier is priced at £165,000 in the UK, inclusive of VAT and installation (it weighs 60kg, so this is helpful) and will begin shipping in November in silver, black, or custom painted finishes. And why not grab the Relentless Mono amps to complete the set? Only £275,000 per pair...
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