MODEL 555 Stereo Amplifier

The Jeff Rowland Model 555 is a stereo power amplifier developed by the Jeff Rowland Design Group and rated as a Class AB amplifier. It delivers 150 watts per channel at 8 ohms and 300 watts per channel at 4 ohms in stereo mode. The amplifier is bridgeable, providing 400 watts at 8 ohms in mono mode.

It is noted for its smooth, dynamic, powerful, and natural sound, and often described as offering a "velvety black background", being capable of elevating a system's performance beyond expectations.
The Model 555 is considered by many owners to be a "forever amplifier".

MODEL 555 SPECIFICATIONS

The input stage uses a transimpedance circuit with error correction to achieve an extremely low high-frequency distortion of less than 0.003% above 10 kHz. Achieving this low level was a challenging R&D challenge, and it's no exaggeration to say that the majority of the design and development time was spent on achieving this low distortion rate. The result is pronounced low-level dynamics, greatly enhancing the reproduction of musical performances. Even the slightest differences in sound pressure at low levels are accurately reproduced, creating subtle dynamic shadings that envelop the listener in a more realistic soundstage.

150W + 150W Bridge Mode Boasts a High Output of 330W
The Model 555 is also very flexible in how it can be used. When used as a stereo amplifier, the typical output is 150W + 150W at an 8Ω load, or 250W + 250W at a 4Ω load. When configured as a monoblock using the MONO input and speaker output, the amplifier boasts a high output of 330W. Since both the input and output are provided separately for mono operation, it can easily be used as a monoblock.

Equipped With an Qmorphous Core Input Transformer
Because an amorphous core input transformer is used, harmonic distortion increases slightly at frequencies below 1 kHz. The transformer used is manufactured by Lundahl and is the same amorphous core input transformer previously used in the Model 735 amplifier. This transformer reproduces an extremely natural tonal balance and provides excellent musical expression, but its drawback is that it takes time to break in, up to 400 hours in our experience. However, Jeff Rowland says that the sacrifice of time is worth it when it comes to playing irreplaceable, beautiful music.

Monoblock Aluminum Chassis
The Model 555 chassis is precision machined from a single block of aluminum. Because it is a one-piece design, it is extremely efficient in terms of heat conduction and heat dissipation. It also provides RFI, EMI shielding, resonance suppression, and minimizes microphonic effects.

This one-piece chassis, pioneered by Jeff Rowland DG, is crafted from aircraft-grade hard aluminum, carefully machined from a block of hard aluminum cut to the same size as the amplifier. It's a monocoque chassis (separate from the front panel). With a monocoque chassis amplifier like this, the temperature of the entire chassis is the same both inside and outside. While it may feel slightly warm to the touch, the heat is dispersed and dissipated throughout, completely negating any impact on the components. In addition to heat dispersion, a monocoque chassis's benefits include its robustness against vibration. External vibrations travel from the speakers through the floor or are reflected by the walls in the listening room, reaching the amplifier and vibrating the chassis. However, the one-piece hard aluminum chassis minimizes the impact of these vibrations, amplifying the audio signal while protecting it. This results in an amplifier with a low noise floor, prominent audio signals, and a high-speed response.

Switch Mode Power Supplies
The amplifier is powered by the renowned switch-mode power supply, which Jeff Rowland Design Group has been using since 1999. While this method offers excellent power efficiency, its purpose is to deliver DC power to the amplifier circuitry at or near the same level as battery power supplies. Power supplies using a combination of capacitors and diodes invert the negative portions of 50 sine waves (60 in some cases) per second to create 100-voltage peaks, and fill the valleys between the peaks with electricity stored in the capacitors. This does not result in perfect DC (the current is not linear, but rather has some bumps). Switch-mode power supplies, however, break down the peaks to 40,000 per second, resulting in a DC power supply that is as close to DC as possible. The effectiveness of this power supply is reflected in the sound quality, confirming the long-standing assertion by critics that the power supply determines the quality of a power amplifier.

High-Performance Power Transistors
The output stage is an analog amplifier using Class AB transistors. Its defining features are its rapid response and dynamics. When viewed in terms of the time axis of sound onset and collapse, an amplifier's overwhelmingly rapid response is a pleasure to listen to. More than simply excellent transients, a sound emerges from a pitch-black, noiseless background and then instantly fades away, at which point the next note emerges. Timing—time axis alignment (phase)—and timbre (tonal balance) are crucial elements in music. The Model 555 is an amplifier that accurately conveys the musician's recordings to the listener.

Fully balanced design for complete noise reduction
Jeff Rowland Design Group amplifiers have used balanced amplification circuits since the 1990s. Of course, the Model 555 is also a fully balanced amplifier. It is a fully balanced differential amplifier to amplify the music signal as is. It achieves low noise and ultra-low distortion even with dynamic signals.

Balanced amplification amplifies the difference between sine waves. Because it is the difference between plus and minus, the signal level is amplified twice as much compared to unbalanced amplification. On the other hand, there is some noise on both sides, but this noise is common mode noise (in phase), and if the difference between plus and minus is the same level, it will cancel out and not appear in the output.

Teflon coated internal wiring
The cables used for input and output signals are Teflon-insulated. Energy is not stored in the insulation, but dissipates naturally as the audio signal fades away. This allows the sound to rise and fade out from extremely deep silence.

To ensure that the music signal is amplified and transmitted without any loss, attention has been paid to the internal wiring cables as well, with thorough noise prevention measures. The speaker output terminals use twisted cables with Teflon-protected silver wires, the input uses a Teflon-shielded low-loss shielded data cable, and the power supply cable uses a PVC twisted cable for noise attenuation. In this way, Jeff Lowland has taken every possible measure to prevent noise by using Teflon at key points. The signal entering the amplifier is amplified to the power needed to drive the speakers, eliminating unnecessary external interference and protecting the music signal.

Contact American Sound Distribution for more information on this new model!

MODEL 925 Mono Amplifier

The Model 925 represents the ultimate benchmark of dynamic realism and expressive refinement. A quarter century of engineering passion expressed in the synergy of advanced technologies and timeless design. A stunning achievement inspired by the musicality of an enduring classic: the Rowland Model 9.

- Quad chassis precision-machined from solid bar-stock T-6061 aircraft grade aluminum providing exceptional thermal heat transfer/dissipation, RFI/EMI shielding, and resonance control.

- The amplifier and power supply of each channel are isolated from each other in separate chassis. High-current DC power and low-current control signals are transferred between the amplifier and power supply via custom made detachable cables.

- Active Power Factor Correction (PFC) in the power supply reduces AC line harmonic noise pollution and increases AC line power utilization to 93%.

- Voltage and current demands from the amplifier remain in phase with each other which eliminates the transient, out-of-phase, high current pulses common to the operation of all other non-PFC audio power amplifiers.

- Powerful, efficient, 2500W switch-mode power supply provides optimum voltage regulation for all circuits and operating conditions, and allows for quiet operation over a wide range of AC mains power sources.

- The power supply is comprised of four DC to DC converters incorporating “zero-current-switching” technology for high-efficiency and greatly reduced levels of conducted and radiated noise.

- An isolated, discrete component, shunt-regulated power supply, providing over 130 decibels of noise isolation, offers low broadband noise and output impedance. This supplies noise-free DC power to all low-level audio circuitry for battery-like performance.

Read Stereophile's "Recommended Equipment" post (from CES 2010).

Visit JRDG's MODEL 925 knowledgebase website for access to the user manuals and more.

MODEL 925 SPECIFICATIONS

MODEL 825 Stereo Amplifier

The Model 825 represents the ultimate benchmark of dynamic realism and expressive refinement. A quarter century of engineering passion expressed in the synergy of advanced technologies and timeless design. A stunning achievement inspired by the musicality of an enduring classic: the Rowland Model 8.

- Dual chassis precision-machined from solid bar-stock T-6061 aircraft grade aluminum providing exceptional thermal heat transfer/dissipation, RFI/EMI shielding, and resonance control.

- The amplifier and power supply are isolated from each other in separate chassis. High-current DC power and low-current control signals are transferred between the amplifier and power supply via custom made detachable cables.

- Active Power Factor Correction (PFC) in the power supply reduces AC line harmonic noise pollution and increases AC line power utilization to 93%. Voltage and current demands from the amplifier remain in phase with each other which eliminates the transient, out-of-phase, high current pulses common to the operation of all other non-PFC audio power amplifiers.

- Powerful, efficient, 2500W switch-mode power supply provides optimum voltage regulation for all circuits and operating conditions, and allows for quiet operation over a wide range of AC mains power sources.

- Innovative class-D audio power technology is based upon a non-hysteresis 5th order self-oscillating control loop taking feedback only at the speaker output.

- Unique output circuitry ensures an extremely low distortion level of less than 0.004% THD + Noise over the entire audio spectrum of 20 Hz to 20 kHz powering any load ranging from 2 to 8 Ohms.

- A power efficiency of 93% at full power output afforded by this technology ensures low energy consumption, low operating temperature, and an extended service life of all components within the amplifier.

- Removable 3-point self-leveling Delron chassis supports provide high frequency mechanical noise isolation.

MODEL 825 REVIEW(S)

Marc Mickelson of The Audio Beat - December 2015
JRDG product video posted by Brandon Kelley (Dec. 2013)

Visit JRDG MODEL 825 knowledgebase website.

MODEL 825 Specifications

MODEL 725 Mono Amplifier

The Model 725 features a unique composite circuit architecture incorporating separate Class AB voltage and current gain blocks with no overall negative feedback.

- Precision-machined chassis with integrated heatsinks, milled from a solid block of aircraft grade 6061-T6 aluminum, provides exceptional thermal heat transfer/dissipation, RFI/EMI shielding, and resonance control.

- All audio circuits are implemented on mil-spec, multi-layer, low dielectric constant, Rogers™ ultra-rigid ceramic circuit board substrate for extremely low energy retention and absorption. Large low impedance ground plane areas for extended internal star-grounding.

- Inherent cancellation effects of balanced topology implemented throughout all power and input/output circuits ensures greatly reduced distortion and noise under dynamic signal conditions.

- High current, dual polarity, ultra low impedance copper bus-bars distribute both power supply input current and signal output current, virtually eliminating intra-circuit EMI signal contamination, greatly reducing internal wiring, while increasing circuit board rigidity.

- Extensive use of Lead (Pb)-free, low temperature coefficient, active and passive surface-mount components results in significantly smaller loop areas, reduced circuit capacitance and inductance, and introduces less noise than conventional leaded components.

- Highly efficient, compact, light weight, 1500 watt DC switch-mode power supply provides optimum voltage regulation for all circuits and operating conditions, and allows for quiet operation over a wide range of AC mains power sources.

- Dual CE approved speaker output terminals require no tools for secure, low resistance connections, and allow for easy bi-wiring applications.

- Removable 3-point self-leveling Delron chassis supports provide high frequency mechanical noise isolation.

MODEL 725 REVIEW(S)

Absolute Sound (Robert Harley - Jan. 2013) Model 725s and Corus Preamp.
The Audio Beat (Roy Gregory - Sept. 2013)
Visit JRDG MODEL 725 knowledgebase website.

MODEL 725 Specifications

MODEL 625 S2 Stereo Amplifier

The 625 Series 2 incorporates many of the same technical features of the 725 amplifiers. Similar to the 725, the 625 S2 signal circuitry is built upon a Rogers ceramic circuit board laminate material for lower dielectric absorption and energy storage. The 4-Pole filter capacitors used in the 725 power supply have also been included in the S2, significantly reducing power supply output noise. The maximum output power has been increased from 300 to 325 watts per channel at 8 ohms.

Precision LED based current sources have been implemented throughout the amplifier circuitry, along with 0.1% thin film SMD resistors for more stable operating points and lower noise. Custom designed Lundahl input transformers are implemented with a higher turns ratio and wound with Cardas high purity copper wire.

Input circuitry includes an additional linear phase 2 pole filter to effectively attenuate all out-of-band signals from any source, including DSD spurious noise.Cardas gold/teflon/rhodium XLR input connectors are carried over from the 725. Newly developed error-correction circuitry has been incorporated around the entire amplifier, making a total of three independent error-correction techniques used to decrease all forms of distortion throughout the entire audio bandwidth.

The Model 625 S2 delivers a sensuous grain-free musicality of unparalleled transparency and low level resolution that blossoms from a rich velvety silence and blossoms into the pure enjoyment of your listening experience.

REVIEWs / DOWNLOADS

HiFi Plus (Roy Gregory - Jan. 2012) - Model 625 and Corus Preamp.
Visit JRDG MODEL 625knowledgebase website.
Download the JRDG product brochure.

MODEL 625 S2 Specifications

CONDUCTOR

The long-awaited phono amplifier from Jeff Rowland
The Phono amp that brings out all the music recorded on analog discs, Jeff Rowland Design Group has released the long-awaited Conductor phono amplifier. The Conductor's inputs come standard with one MC input, with options for up to four. Each input circuit is housed in its own separate chamber, eliminating interference. Three types of input modules are available: a standard MC module, a high-grade amorphous-core MC module, and an MM module.

Compatible with almost all commercially available MM, high-output MM, MC, and low-output MC cartridges.

All MC inputs and main outputs have balanced (XLR) and single-ended (RCA) connections. While the MM input option only has RCA input jacks, all inputs and outputs are transformer coupled for superior noise rejection and inter-circuit interference immunity. There is no gain difference between balanced and single-ended inputs and outputs in a pair.

Specifications

MODEL 125 Stereo Amplifier

The Model 125 stereo bridgeable power amplifier delivers dynamic realism and refinement from its solid aircraft-grade aluminum chassis, a perfect match for the sleek profile of its companion Capri S2 preamplifier. From a single M125 in stereo mode powering an intimate analog system, up to several bridged units driving a multi-speaker setup, down to a bridged pair controlling demanding 4-Ohm monitors, the energy-efficient Model 125 power amplifier delivers consistent resolution and authority with Rowland finesse.

REVIEWS/DOWNLOADS

the Audio Beat Capri S2 and the Model 125 (August 2016)
MODEL 125 brochure
Visit JRDG MODEL 125 knowledgebasewebsite.

MODEL 125 Specifications

Daemon Integrated Amplifier

- A 1500W SUPER INTEGRATED AMPLIFIER

Jeff Rowland Design Group launched the 1500 WPC Daemon Super Integrated Amplifier at Munich High End 2015. Named after the ancient Greek word for the power of “creative genius” and the spirit of “scientific inspiration”, the Daemon represents a technological leap forward as Jeff Rowland’s fifth generation of integrated amplifiers.

The Daemon is one of JRDG's most sophisticated products to date. You’ll see much of it's DNA expressed in future products according to Jeff Rowland. The 1500 WPC dual mono integrated amplifier is machined from solid bars of 6061-T6 aluminum by Vertec Tool in Colorado Springs. Vertec has been sculpting Rowland products for over 25-years. Vertec’s creativity and expertise can be felt in the Daemon’s precision weighted volume bezel. Mounted between two industrial grade bearings, the volume bezel provides exquisitely tactile access to a 99.5 dB range in 0.5 dB increments.

Jeff Rowland has partnered with Thomas Holm, designer of the Aeris DAC and Continuum S2 digital circuitry, to develop both analog and the digital circuitry for the Daemon. For ultimate isolation, the digital and analog power supplies are completely separated and have individual local regulation at point of load. 6-layer Rogers ceramic circuit boards are used throughout.

The 7” x 5” (178 x 127 mm) Touch Screen Interface was designed in collaboration with Danish user interface design house Mjölner. The machined aluminum hand held remote incorporates the latest BlueTooth Low Energy technology, providing control for the most common device functions and permitting full navigation of the touch screen interface.

The amp also comes with a fully isolated headphone amplifier and a 1/4” output jack integrated in the face of the Delrin base for easy access.

The base itself provides excellent isolation for the Daemon on almost any surface, and milled with threaded holes accepting standard footers if desired.

Optional features include: HDMI IN/OUT plug-in module; WiFi plug-in streaming module; and an internally installed MC/MM phono module. The firmware is updatable via a dedicated USB port. The Daemon’s universal auto-ranging power supply ensures trouble free operation throughout the world.

Daemon Reviews / Excerpts

AVshowreports Show Winner, RMAF 2016 with Jeff Rowland on the Daemon - Youtube Video
AVshowreports New York Audio Show 2016 with Jeff Rowland on the Daemon - Youtube Video
AVshowreports RMAF 2015 with Jeff Rowland and the Daemon on Youtube
Facebook video post featuring the Daemon - October 2015
Novo Press (previously CANADA HiFi) Jan. 2015

Download the Daemon product brochure.

Daemon Specifications

Continuum S2 Integrated Amplifier

Featuring enhanced sonic performance and flexibility, the Rowland Continuum Series 2 integrated amplifier delivers stunning dynamic realism and expressive refinement through advanced topologies. Continuum S2 integrates the Capri S2 preamplification circuit, input/output, and control features with an innovative 400 watt power amplification stage into a single chassis.

The amplifier delivers the trademark Rowland musicality, resolution, and unfailing authority to the most refined audio environments: challenge Continuum S2 to the extreme dynamics of high-resolution digital sources and the power requirements of large bi-wired speakers. Apply it to the complex loads of electrostatic panels in analog rigs. Admire its exceptional realism driving single-wired studio monitors in a sophisticated multi-media system.

The elegance of Continuum S2’s ergonomic console emerges from a solid block of aircraft-grade aluminum. Discover the impressive complement of standard input/output interfaces. Enhance its flexibility through the optional DAC card, or its fully redesigned phono stage.

Continum S2 Reviews / Videos / etc.

Positive Feedback ISSUE 72 (Wojciech Pacuła - April 2014)
JRDG product video posted by Brandon Kelley (Dec. 2013)

Visit JRDG CONTINUUM S2 knowledgebase website.

Continum S2 Specifications

Corus Preamplifier

The Corus Stereo Preamplifier delivers the Jeff Rowland hallmark of a sensuous and grain free musicality, combined with astonishing transparency and low level resolution. A broad 3-dimensional sound stage materializes into the physical listening space, where instruments and vocalists assume the textured appearance of solid existence.

The preamplifier yields exceptional frequency extension and linearity, with magnificent bass definition, an extraordinarily complex exposure of harmonic structure, and a sweetly filigreed treble. The Corus yields amazingly nuanced low level detail and micro-dynamics, and outperforms every previous Rowland preamplifier with its transient speed, staggering authority, and breath-taking macro dynamics. Only the transcendent resolving musicality of the Criterion battery-powered Preamplifier ever yields an even superior listening experience.

- Elegant main chassis milled from ingots of non-resonant aircraft-grade aluminum houses all delicate audio and control circuits.

- Ground-breaking AC power supply is segregated in its own handsome external milled aluminum unit.

Corus Reviews

Absolute Sound (Robert Harley - Jan. 2013) Model 725s and Corus Preamp.
Hi-Fi+Corus Preamp and the Model 625 Power amp (Roy Gregory - Jan 2012)

Visit JRDG CORUS knowledgebase website.
JRDG Corus Brochure

Corus Specifications

Capri S2 Preamplifier

The Capri S2 features an impressive complement of standard input/output interfaces; greatly enhanced flexibility through its optional DAC card or phono option; and the Rowland trademark prismatic platinum faceplate beautifully integrated into a non-resonant chassis milled from a solid block of aluminum.

With an output impedance of only 80 Ohms balanced and 40 Ohms single ended, Capri S2 drives any amplifier with confidence. Whether serving a single-ended triode amplifier in a vinyl rig, or controlling a quartet of solid-state Rowland M525 monoblocks with a 192 kHz digital source, or at the nexus of a home theater setup, the Capri S2 preamplifier delivers the trademark Rowland musicality, resolution, and consistent authority.

Featuring unprecedented sonic performance and functional enhancements, the Capri Series 2 preamplifier offers stunning dynamic realism and expressive refinement through an advanced topology.

Capri S2 Reviews

Audiophilia Star Component Award May 28th 2016 - Anthony Kershaw
Audio Beat Capri S2 and the Model 125 (August 2016).

Visit JRDG CAPRI S2 knowledgebase website.

Capri S2 Specifications

Aeris DAC

Based upon an asynchronous buffer, voltage controlled crystal oscillators and a 24 bit D/A converter under the precise control of an FPGA running proprietary algorithms.

Nexus of time and space; dynamic gateway between digital and analogue worlds. HYBRID from Latin aerius – ‘air’ or ‘atmosphere,’ and late Latin aera – denoting an epoch from which time is reckoned.

The Aeris is the product of a close collaboration between Jeff Rowland Design Group and Holm Acoustics, a Danish company founded by Thomas Holm that specializes in signal processing products for high end audio applications.

The Aeris is much more than the successful result of a synergistic collaboration between the two companies. The high degree of complementary synergy between the two teams working in parallel can only be defined as a case of true organic design.

Aeris DAC brochure
Visit JRDG AERIS knowledgebasewebsite.

Aeris Specifications