{"id":9564,"date":"2010-04-26T22:00:17","date_gmt":"2010-04-26T20:00:17","guid":{"rendered":"http:\/\/www.hifi-advice.com\/blog\/?page_id=9564"},"modified":"2022-12-25T12:00:18","modified_gmt":"2022-12-25T10:00:18","slug":"jrdg-company-special-model-925-and-825","status":"publish","type":"page","link":"https:\/\/www.hifi-advice.com\/blog\/jeff-rowland-power-amplifiers\/jrdg-company-special-model-925-and-825\/","title":{"rendered":"JRDG Company Special – Model 925 and 825"},"content":{"rendered":"

<\/b>Model\u00a0925<\/strong><\/h2>\n

2011-2022 (was not available in the Netherlands until 2013)<\/strong>
\nRetail price in 2013\u00a0in the Netherlands 69.500 euro
\nRetail price in 2016\u00a0in the Netherlands 81.000 euro<\/p>\n

\"rowland-925_550pix\"<\/p>\n

For a while, the 925 was no longer available in the Netherlands. In the meantime the 725 got introduced. Was it to be the replacement for the big 925? Now we know it was not, but for a while it seemed that Rowland had phased out the 925, judging from its absence from the 2012 brochure. Not compliant with EU regulations perhaps? Who knows. Fact is that it became available again (I even heard a pair at a demo) in 2013. JRDG do not disclose the precise amplification method used but it seems that the 925 employs nCore modules, this in contrast to the Pascal modules used for all their other switching amps, although I am not sure about the 825.<\/p>\n

Model 825<\/strong><\/h2>\n

2013-2022<\/strong>
\nRetail price in 2013\u00a0in the Netherlands 38.500\u00a0euro
\nRetail price in 2016\u00a0in the Netherlands 42.000 euro<\/p>\n

\"rowland-825_550pix\"<\/h2>\n

It’s not clear to me which amplification modules are used but it must be either nCore or Pascal.<\/p>\n

\n

Model 925 Pictures<\/h2>\n

\"rowland-model-925-0923c443d_500pix\"<\/p>\n

\"rowland-925-set-500pix\"<\/p>\n

Prototype with flat-sided (no air vents) power supply<\/p>\n

\"rowland-model-925-05_550pix\"<\/p>\n

\n

Model 825 Pictures<\/h2>\n

\"rowland-corus-psu-aeris-en-825-hvp-veldhoven-2016_550pix\"<\/p>\n

\"rowland-corus-psu-aeris-en-825-hvp-veldhoven-2016-close_550pix\"<\/p>\n

Model 825 at an audio show in 2016 in Veldhoven, the Netherlands.<\/p>\n

\n

625\/725 and 825\/925 differences<\/b><\/h2>\n

The 725’s use ceramic boards and some other novel tricks, which are said to make them sound more nuanced and transparent than the 625. While the 625 and 725 on their basic levels share similar technology, both being “traditional” analog bipolar transistor types, the 925, and I assume also the 825 which looks like a spin-off from the 925, are actually \u00a0switch mode\u00a0amplifiers using Pascal modules at their core, augmented with a lot of extra power regulation.<\/p>\n

\n

Model 925 Features<\/h2>\n

MACHINED ALUMINUM CHASSIS
\nQuad chassis precision-machined from solid bar-stock T-6061 aircraft grade aluminum providing exceptional thermal heat transfer\/dissipation, RFI\/EMI shielding, and resonance control.<\/p>\n

FUNCTIONAL ISOLATION
\nThe 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.<\/p>\n

ACTIVE POWER FACTOR CORRECTION
\nActive 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.<\/p>\n

HIGH-EFFICIENCY SWITCH-MODE POWER SUPPLY
\nPowerful, 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.<\/p>\n

ZERO-CURRENT SWITCHING
\nThe power supply is comprised of four DC to DC converters incorporating \u201czero-current-switching\u201d technology for high-efficiency and greatly reduced levels of conducted and radiated noise.<\/p>\n

4 POLE CAPACITORS
\nCustom-made 4-pole capacitors integrated within the power supply further reduce any remaining residual noise.<\/p>\n

NOISE ISOLATION
\nAn 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.<\/p>\n

SOLID-STATE RELAY
\nAC Mains power is switched via a solid-state relay. Switching occurs only during the AC mains zero voltage crossing period dramatically reducing in-rush current during turn-on surges and providing a lifetime of trouble-free switching.<\/p>\n

CERAMIC CIRCUIT BOARDS
\nAll input circuitry is implemented on mil-spec, multi-layer, low dielectric constant, Rogers\u2122 ultra-rigid ceramic circuit board substrate for extremely low energy retention and absorption.<\/p>\n

BALANCED TOPOLOGY
\nInherent cancellation effects of balanced topology implemented throughout all power and input\/output circuits ensures greatly reduced distortion and noise under dynamic signal conditions.<\/p>\n

HIGH-PRECISION SURFACE MOUNT COMPONENTS
\nExtensive 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.<\/p>\n

THIN FILM RESISTORS
\nAll resistors are low-noise, 0.1% thin film Surface Mount Devices (SMD) type for extremely low thermal noise which complements the low-noise characteristics of the active circuitry.<\/p>\n

TRANSFORMER-COUPLING AND ISOLATION
\nTransformer coupled input circuitry provides universal component compatibility, excellent common-mode noise rejection (CMRR) from the input source, and virtually eliminates ground loop noise and RFI\/EMI. Transformer coupling ensures identical amplifier overall gain when using unbalanced inputs.<\/p>\n

REAR PANEL CONTROLS
\nRear panel switching of input phase, overall gain, and input selection (XLR\/RCA).<\/p>\n

CUSTOM INPUT JACKS
\nBoth XLR and RCA input jacks are custom-made Cardas connectors constructed of copper, rhodium, gold, and Teflon materials for minimal signal loss and excellent corrosion resistance.<\/p>\n

CUTTING-EDGE OUTPUT CIRCUITRY
\nInnovative class-D audio power technology is based upon a non-hysteresis 5th order self-oscillating control loop taking feedback only at the speaker output.<\/p>\n

EXTREMELY LOW DISTORTION
\nUnique 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.<\/p>\n

STABILITY AND FLEXIBILITY
\nAn output impedance of less than 0.003 Ohms (3 milliohms) over the entire frequency range of 20 Hz to 20 kHz ensures that all loudspeaker types can be driven with impunity. Stability of the amplifier is guaranteed under all conditions when driving any loudspeaker or loudspeaker cable type.<\/p>\n

ERROR DETECTION
\nExtensive microprocessor controlled error detection circuitry ensures protection of associated loudspeaker components under many extreme operating conditions.<\/p>\n

HIGH-EFFICIENCY
\nA 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.<\/p>\n

PARALLEL BINDING POSTS
\nDual CE approved speaker output terminals require no tools for secure, low resistance connections, and allow for easy bi-wiring applications.<\/p>\n

FLEXIBLE 20 AMP AC POWER
\n20 amp AC power inlet accepts a wide variety of after-market high-performance power cables.<\/p>\n

FRONT PANEL STANDBY BUTTON
\nIlluminated front panel push-button switches the amplifier into standby mode. Separate stand-by circuitry reduces AC mains power to less than 1 watt during stand-by, ensuring international regulatory compliance.<\/p>\n

REMOTE ON\/OFF
\nA 1\/8\u201d (3.5mm) mini plug connector on rear panel permits amplifier power on\/standby switching in remote and home theater applications.<\/p>\n

SELF-LEVELING SUPPORTS
\nRemovable 3-point self-leveling Delron chassis supports provide high frequency mechanical noise isolation.<\/p>\n

Model 925 Technical Specifications<\/h2>\n

4-chassis mono power amp<\/p>\n

Balanced design<\/p>\n

Class A\/B<\/p>\n

OUTPUT POWER
\n430 watts @ 8 ohms\/850 watts @ 4 ohms<\/p>\n

POWER SUPPLY
\n2400 W regulated DC SMPS per channel, with Active Power Factor Correction (PFC).<\/p>\n

FREQUENCY RESPONSE
\n5 Hz – 50 kHz<\/p>\n

INPUT IMPEDANCE
\n40k ohms<\/p>\n

THD + NOISE
\n0.004%, 20 Hz- 20 kHz<\/p>\n

DAMPING FACTOR
\n> 1000, 20 Hz – 20 kHz<\/p>\n

OVERALL GAIN
\nSwitchable 26\/32 dB<\/p>\n

Combined AMPLIFIER chassis & POWER SUPPLY chassis WEIGHT
\n160.4 lb \/ 73 kg (per channel)<\/p>\n

TOTAL DIMENSIONS (H\/W\/D)
\n16.5″ x 15.5″ x 16.25″ (per channel) 419mm x 394mm x 413mm<\/p>\n

\n

Model 825 Features<\/h2>\n

MACHINED ALUMINUM CHASSIS
\nDual chassis precision-machined from solid bar-stock T-6061 aircraft grade aluminum providing exceptional thermal heat transfer\/dissipation, RFI\/EMI shielding, and resonance control.<\/p>\n

FUNCTIONAL ISOLATION
\nThe 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.<\/p>\n

ACTIVE POWER FACTOR CORRECTION
\nActive 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.<\/p>\n

HIGH-EFFICIENCY SWITCH-MODE POWER SUPPLY
\nPowerful, 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.<\/p>\n

ZERO-CURRENT SWITCHING
\nThe power supply is comprised of four DC to DC converters incorporating \u201czero-current-switching\u201d technology for high-efficiency and greatly reduced levels of conducted and radiated noise.<\/p>\n

4 POLE CAPACITORS
\nCustom-made 4-pole capacitors integrated within the power supply further reduce any remaining residual noise.<\/p>\n

NOISE ISOLATION
\nAn 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.<\/p>\n

SOLID-STATE RELAY
\nAC Mains power is switched via a solid-state relay. Switching occurs only during the AC mains zero voltage crossing period dramatically reducing in-rush current during turn-on surges and providing a lifetime of trouble-free switching.<\/p>\n

CERAMIC CIRCUIT BOARDS
\nAll input circuitry is implemented on mil-spec, multi-layer, low dielectric constant, Rogers\u2122 ultra-rigid ceramic circuit board substrate for extremely low energy retention and absorption.<\/p>\n

BALANCED TOPOLOGY
\nInherent cancellation effects of balanced topology implemented throughout all power and input\/output circuits ensures greatly reduced distortion and noise under dynamic signal conditions.<\/p>\n

HIGH-PRECISION SURFACE MOUNT COMPONENTS
\nExtensive 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.<\/p>\n

THIN FILM RESISTORS
\nAll resistors are low-noise, 0.1% thin film Surface Mount Devices (SMD) type for extremely low thermal noise which complements the low-noise characteristics of the active circuitry.<\/p>\n

TRANSFORMER-COUPLING AND ISOLATION
\nTransformer coupled input circuitry provides universal component compatibility, excellent common-mode noise rejection (CMRR) from the input source, and virtually eliminates ground loop noise and RFI\/EMI. Transformer coupling ensures identical amplifier overall gain when using unbalanced inputs.<\/p>\n

REAR PANEL CONTROLS
\nRear panel switching of input phase, overall gain, and input selection (XLR\/RCA). A \u201clink switch\u201d permits electrical linking of both right and left channels for bi-wiring applications.<\/p>\n

CUSTOM INPUT JACKS
\nBoth XLR and RCA input jacks are custom-made Cardas connectors constructed of copper, rhodium, gold, and Teflon materials for minimal signal loss and excellent corrosion resistance.<\/p>\n

CUTTING-EDGE OUTPUT CIRCUITRY
\nInnovative class-D audio power technology is based upon a non-hysteresis 5th order self-oscillating control loop taking feedback only at the speaker output.<\/p>\n

EXTREMELY LOW DISTORTION
\nUnique 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.<\/p>\n

STABILITY AND FLEXIBILITY
\nAn output impedance of less than 0.003 Ohms (3 milliohms) over the entire frequency range of 20 Hz to 20 kHz ensures that all loudspeaker types can be driven with impunity. Stability of the amplifier is guaranteed under all conditions when driving any loudspeaker or loudspeaker cable type.<\/p>\n

ERROR DETECTION
\nExtensive microprocessor controlled error detection circuitry ensures protection of associated loudspeaker components under many extreme operating conditions.<\/p>\n

HIGH-EFFICIENCY
\nA 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.<\/p>\n

PARALLEL BINDING POSTS
\nDual CE approved speaker output terminals require no tools for secure, low resistance connections, and allow for easy bi-wiring applications.<\/p>\n

FLEXIBLE 20 AMP AC POWER
\n20 amp AC power inlet accepts a wide variety of after-market high-performance power cables.<\/p>\n

FRONT PANEL STANDBY BUTTON
\nIlluminated front panel push-button switches the amplifier into standby mode. Separate stand-by circuitry reduces AC mains power to less than 1 watt during stand-by, ensuring international regulatory compliance.<\/p>\n

REMOTE ON\/OFF
\nA 1\/8\u201d (3.5mm) mini plug connector on rear panel permits amplifier power on\/standby switching in remote and home theater applications.<\/p>\n

SELF-LEVELING SUPPORTS
\nRemovable 3-point self-leveling Delron chassis supports provide high frequency mechanical noise isolation.<\/p>\n

Model 825 Technical Specifications<\/h2>\n

2-chassis stereo power amp: 1 audio chassis and 1 power supply chassis<\/p>\n

OUTPUT POWER
\n400W @ 8 ohms\/750W @ 4 ohms<\/p>\n

FREQUENCY RESPONSE
\n5 Hz – 50 kHz<\/p>\n

INPUT IMPEDANCE
\n40k ohms<\/p>\n

THD + NOISE
\n0.004%, 20 Hz- 20 kHz<\/p>\n

DAMPING FACTOR
\n> 1000, 20 Hz – 20 kHz<\/p>\n

OVERALL GAIN
\nSwitchable 26\/32 dB<\/p>\n

Combined AMPLIFIER chassis & POWER SUPPLY chassis WEIGHT
\n160.4 lb \/ 73 kg<\/p>\n

TOTAL DIMENSIONS (H\/W\/D)
\n16.5″ x 15.5″ x 16.25″ — 419mm x 394mm x 413mm<\/p>\n

More Jeff Rowland<\/h2>\n

Jeff Rowland Company Special Main Page
\n<\/a>Jeff Rowland Company Special Power Amplifiers<\/a><\/p>\n","protected":false},"excerpt":{"rendered":"

Model\u00a0925 2011-2022 (was not available in the Netherlands until 2013) Retail price in 2013\u00a0in the Netherlands 69.500 euro Retail price in 2016\u00a0in the Netherlands 81.000 euro For a while, the 925 was no longer available in the Netherlands. In the meantime the 725 got introduced. Was it to be the replacement for the big 925? […]<\/p>\n","protected":false},"author":1,"featured_media":0,"parent":8319,"menu_order":0,"comment_status":"open","ping_status":"closed","template":"","meta":{"footnotes":""},"class_list":["post-9564","page","type-page","status-publish","hentry"],"_links":{"self":[{"href":"https:\/\/www.hifi-advice.com\/blog\/wp-json\/wp\/v2\/pages\/9564","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/www.hifi-advice.com\/blog\/wp-json\/wp\/v2\/pages"}],"about":[{"href":"https:\/\/www.hifi-advice.com\/blog\/wp-json\/wp\/v2\/types\/page"}],"author":[{"embeddable":true,"href":"https:\/\/www.hifi-advice.com\/blog\/wp-json\/wp\/v2\/users\/1"}],"replies":[{"embeddable":true,"href":"https:\/\/www.hifi-advice.com\/blog\/wp-json\/wp\/v2\/comments?post=9564"}],"version-history":[{"count":11,"href":"https:\/\/www.hifi-advice.com\/blog\/wp-json\/wp\/v2\/pages\/9564\/revisions"}],"predecessor-version":[{"id":33945,"href":"https:\/\/www.hifi-advice.com\/blog\/wp-json\/wp\/v2\/pages\/9564\/revisions\/33945"}],"up":[{"embeddable":true,"href":"https:\/\/www.hifi-advice.com\/blog\/wp-json\/wp\/v2\/pages\/8319"}],"wp:attachment":[{"href":"https:\/\/www.hifi-advice.com\/blog\/wp-json\/wp\/v2\/media?parent=9564"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}