Jeff Rowland Model 735 Mono Block Power Amplifiers

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Jeff Rowland Model 735 Mono Block Power Amplifiers

Jeff Rowland Model 735 Mono Block Power Amplifiers

$38,999.00 Free Shipping!

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Jeff Rowland Model 735 Mono Block Power Amplifiers

$38,999.00 Free Shipping!

Free Shipping!
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  • Description

     

     

    MY TAKE: Wow, just wow, these are flat our amazing amplifiers! Striking beauty, stunning sound, rock-solid reliability - a complete package. Few products offer the complete satisfaction and pride of ownership you’ll experience with the purchase of a Jeff Rowland component. – Galen Carol

     

    Since the ending of the production of the popular Model 725 Mono Amplifier in 2018, there has been an increasing demand for a replacement of this fine amplifier for use by discriminating music lovers and audiophiles worldwide.


    By using the Model 725 as an acclaimed platform for ongoing research and development, a number of changes have been incorporated into the design of the new Model 735, which are discussed below.


    After many hours of critical listening tests done on several input transformer types, and consultation with Per Lundahl of Lundahl Transformers AB in Sweden, it was decided to incorporate a custom-designed cobalt-based amorphous core input transformer instead of the standard high permeability, mu-metal lamination core type previously used in the 725.


    Despite a slight increase in measured low order harmonic distortion in the low frequencies due to the amorphous construction, the increase in overall musical resolution, richness, and expression throughout the overall frequency range due to the inclusion of this particular transformer became immediately apparent during listening tests.


    Due to the continuing increase of electromagnetic and radio frequency interference and pollution throughout the world, and improved input filter characteristic was incorporated in the input stage of the Model 735 to address this issue. Very small amounts of EMF interference from any source can have deleterious effects on sensitive input stages of all-solid-state circuitry, therefore these measures taken in the Model 735 yielded enhanced musical reproduction and background silence. A reduction of amplifier bandwidth to approximately 90 kHz was chosen and careful filter alignment achieved a very minimal group phase deviation, which guarantees signal fidelity.


    Additional refinement of the error correction circuitry lowered the distortion well above 30 kHz to levels difficult to measure with modern test equipment. Although it may be difficult to determine if these measures yield substantial sonic benefit at this time, I feel it is still an exercise worthy of effort towards the advancement of knowledge and understanding of amplifier circuit operation.


    The ceramic substrate circuit board material is carried over from previous models and has been redesigned in some areas to accommodate some minor circuit improvements and additions. A new color has been chosen for a unique visual identifier.


    A new muting circuit has been incorporated in the output circuitry to reduce noise during turn-on and turn-off transitions.


    A new amplifier bottom cover has been designed with machined cavities to accept a proprietary damping material, secured in place with machined covers, which act as supporting feet for the amplifier. During the testing and evaluation of various damping materials and supporting elements, material and configuration was found which completely isolates the amplifier chassis from its supporting structure, allowing the amplifier to express its full potential.


    A new faceplate power standby button, similar to those used on other products in our line, augments aesthetic compatibility with other JRDG products. Operational status is now indicated with a subtle, white pin-point LED, reducing distraction in darkly lit listening rooms.


    A new non-anodized machined top cover extends the clear faceplate elegance towards the rear of the unit, enhancing contrasting elements of the entire “machined from a solid block" chassis.  


    FEATURES:

     

    • MACHINED ALUMINUM CHASSIS: Precision-machined chassis with integrated heatsinks, milled from a solid block of aircraft-grade aluminum, provides exceptional thermal heat transfer/dissipation, RFI/EMI shielding, and resonance control.
    • CERAMIC CIRCUIT BOARDS: All audio circuits are implemented on mil-spec, multilayer, low dielectric constant, Rogers™ ultra-rigid ceramic circuit board substrate for extremely low energy retention and absorption. Large low impedance ground planes areas for extended internal star-grounding.
    • COMPOSITE CIRCUIT ARCHITECTURE: Unique composite circuit architecture incorporating separate Class AB voltage and current gain blocks with an innovative error correction loop, delivering a sensuous grain-free musicality of unparalleled transparency and low-level resolution.
    • BALANCED TOPOLOGY: 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 COPPER BUS-BARS: 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.
    • HIGH-PRECISION SURFACE MOUNT COMPONENTS: 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.
    • TRANSFORMER-COUPLING AND ISOLATION: Transformer coupled input circuitry provides universal component compatibility and virtually eliminate ground loop noise and RFI/EMI. Transformer coupling ensures identical amplifier overall gain when using unbalanced input adapters.
    • POWER FACTOR CORRECTION: Power Factor Correction (PFC) in the power supply reduces AC line harmonic noise pollution and increases AC line power utilization to 99%.
    • HIGH-EFFICIENCY SWITCH-MODE POWER SUPPLY: Highly efficient, compact, lightweight, 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.
      PARALLEL BINDING POSTS: Dual CE approved speaker output terminals require no
      tools for secure, low resistance connections, and allow for easy bi-wiring
      applications.
    • FLEXIBLE 20 AMP AC POWER: 20 amp AC power inlet accepts a wide variety of
      after-market high-performance power cables.
    • FRONT PANEL STANDBY BUTTON: Illuminated front-panel push-button switches the amplifier into standby mode (<0.3 watt consumption).
    • REMOTE ON/OFF: A 1/8” (3.5mm) mini-plug connector on the rear panel permits amplifier power on/standby switching in remote and home theater applications.
    • IMPROVED AMPLIFIER ISOLATION: Proprietary damping material on the bottom of the amplifier chassis completely isolates the amplifier from its supporting
      structure.


    SPECIFICATIONS:


    Output Power:  330 watts @ 8 ohms / 650 watts @ 4 ohms
    Frequency Response: 5 Hz - 90 kHz, - 3 dB
    S/N Ratio: 95 dB, ref. 1.0 watt @ 8 ohm load
    Output Noise: <55 μv, 20 Hz – 20 kHz, unweighted
    Input Impedance: 40k ohms
    THD + Noise: <0.001% from 2.0 kHz - 20 kHz, gradually increasing below 2.0 kHz due to amorphous core input transformer
    Damping Factor: >500, 20 Hz - 20 kHz
    Overall Gain / Bal. or Unbal.: 26 dB
    Common Mode Rejection Ratio: > 90 dB, 20 Hz – 20 kHz
    Absolute Phase: Non-inverting Pin 2 Positive
    Inputs Balanced: (XLR)
    Outputs: 2 pair parallel binding posts
    Power Consumption: Idle 85 watts/VA, power factor corrected at all power levels
    Power Consumption: Standby 0.3 watt
    Amplifier Weight: 54 lbs. / 24.5 kg (each)
    Amplifier Shipping: Weight 64 lbs. / 29 kg (each)
    Amplifier Dimensions: (h/w/d) 5.75” x 15.5” x 16.25” / 146mm x 394mm x 413mm (each)

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Jeff Rowland Model 735 Mono Block Power Amplifiers

$38,999.00 Free Shipping!

Free Shipping!
Loading...

Description

 

 

MY TAKE: Wow, just wow, these are flat our amazing amplifiers! Striking beauty, stunning sound, rock-solid reliability - a complete package. Few products offer the complete satisfaction and pride of ownership you’ll experience with the purchase of a Jeff Rowland component. – Galen Carol

 

Since the ending of the production of the popular Model 725 Mono Amplifier in 2018, there has been an increasing demand for a replacement of this fine amplifier for use by discriminating music lovers and audiophiles worldwide.


By using the Model 725 as an acclaimed platform for ongoing research and development, a number of changes have been incorporated into the design of the new Model 735, which are discussed below.


After many hours of critical listening tests done on several input transformer types, and consultation with Per Lundahl of Lundahl Transformers AB in Sweden, it was decided to incorporate a custom-designed cobalt-based amorphous core input transformer instead of the standard high permeability, mu-metal lamination core type previously used in the 725.


Despite a slight increase in measured low order harmonic distortion in the low frequencies due to the amorphous construction, the increase in overall musical resolution, richness, and expression throughout the overall frequency range due to the inclusion of this particular transformer became immediately apparent during listening tests.


Due to the continuing increase of electromagnetic and radio frequency interference and pollution throughout the world, and improved input filter characteristic was incorporated in the input stage of the Model 735 to address this issue. Very small amounts of EMF interference from any source can have deleterious effects on sensitive input stages of all-solid-state circuitry, therefore these measures taken in the Model 735 yielded enhanced musical reproduction and background silence. A reduction of amplifier bandwidth to approximately 90 kHz was chosen and careful filter alignment achieved a very minimal group phase deviation, which guarantees signal fidelity.


Additional refinement of the error correction circuitry lowered the distortion well above 30 kHz to levels difficult to measure with modern test equipment. Although it may be difficult to determine if these measures yield substantial sonic benefit at this time, I feel it is still an exercise worthy of effort towards the advancement of knowledge and understanding of amplifier circuit operation.


The ceramic substrate circuit board material is carried over from previous models and has been redesigned in some areas to accommodate some minor circuit improvements and additions. A new color has been chosen for a unique visual identifier.


A new muting circuit has been incorporated in the output circuitry to reduce noise during turn-on and turn-off transitions.


A new amplifier bottom cover has been designed with machined cavities to accept a proprietary damping material, secured in place with machined covers, which act as supporting feet for the amplifier. During the testing and evaluation of various damping materials and supporting elements, material and configuration was found which completely isolates the amplifier chassis from its supporting structure, allowing the amplifier to express its full potential.


A new faceplate power standby button, similar to those used on other products in our line, augments aesthetic compatibility with other JRDG products. Operational status is now indicated with a subtle, white pin-point LED, reducing distraction in darkly lit listening rooms.


A new non-anodized machined top cover extends the clear faceplate elegance towards the rear of the unit, enhancing contrasting elements of the entire “machined from a solid block" chassis.  


FEATURES:

 

  • MACHINED ALUMINUM CHASSIS: Precision-machined chassis with integrated heatsinks, milled from a solid block of aircraft-grade aluminum, provides exceptional thermal heat transfer/dissipation, RFI/EMI shielding, and resonance control.
  • CERAMIC CIRCUIT BOARDS: All audio circuits are implemented on mil-spec, multilayer, low dielectric constant, Rogers™ ultra-rigid ceramic circuit board substrate for extremely low energy retention and absorption. Large low impedance ground planes areas for extended internal star-grounding.
  • COMPOSITE CIRCUIT ARCHITECTURE: Unique composite circuit architecture incorporating separate Class AB voltage and current gain blocks with an innovative error correction loop, delivering a sensuous grain-free musicality of unparalleled transparency and low-level resolution.
  • BALANCED TOPOLOGY: 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 COPPER BUS-BARS: 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.
  • HIGH-PRECISION SURFACE MOUNT COMPONENTS: 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.
  • TRANSFORMER-COUPLING AND ISOLATION: Transformer coupled input circuitry provides universal component compatibility and virtually eliminate ground loop noise and RFI/EMI. Transformer coupling ensures identical amplifier overall gain when using unbalanced input adapters.
  • POWER FACTOR CORRECTION: Power Factor Correction (PFC) in the power supply reduces AC line harmonic noise pollution and increases AC line power utilization to 99%.
  • HIGH-EFFICIENCY SWITCH-MODE POWER SUPPLY: Highly efficient, compact, lightweight, 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.
    PARALLEL BINDING POSTS: Dual CE approved speaker output terminals require no
    tools for secure, low resistance connections, and allow for easy bi-wiring
    applications.
  • FLEXIBLE 20 AMP AC POWER: 20 amp AC power inlet accepts a wide variety of
    after-market high-performance power cables.
  • FRONT PANEL STANDBY BUTTON: Illuminated front-panel push-button switches the amplifier into standby mode (<0.3 watt consumption).
  • REMOTE ON/OFF: A 1/8” (3.5mm) mini-plug connector on the rear panel permits amplifier power on/standby switching in remote and home theater applications.
  • IMPROVED AMPLIFIER ISOLATION: Proprietary damping material on the bottom of the amplifier chassis completely isolates the amplifier from its supporting
    structure.


SPECIFICATIONS:


Output Power:  330 watts @ 8 ohms / 650 watts @ 4 ohms
Frequency Response: 5 Hz - 90 kHz, - 3 dB
S/N Ratio: 95 dB, ref. 1.0 watt @ 8 ohm load
Output Noise: <55 μv, 20 Hz – 20 kHz, unweighted
Input Impedance: 40k ohms
THD + Noise: <0.001% from 2.0 kHz - 20 kHz, gradually increasing below 2.0 kHz due to amorphous core input transformer
Damping Factor: >500, 20 Hz - 20 kHz
Overall Gain / Bal. or Unbal.: 26 dB
Common Mode Rejection Ratio: > 90 dB, 20 Hz – 20 kHz
Absolute Phase: Non-inverting Pin 2 Positive
Inputs Balanced: (XLR)
Outputs: 2 pair parallel binding posts
Power Consumption: Idle 85 watts/VA, power factor corrected at all power levels
Power Consumption: Standby 0.3 watt
Amplifier Weight: 54 lbs. / 24.5 kg (each)
Amplifier Shipping: Weight 64 lbs. / 29 kg (each)
Amplifier Dimensions: (h/w/d) 5.75” x 15.5” x 16.25” / 146mm x 394mm x 413mm (each)