Saturday, January 21, 2012

Jeff Rowland Model 725 mono amplifiers

$28000 /pr

Precision machined from two single blocks of non-resonant aircraft aluminum, the Model 725 features a unique composite circuit architecture incorporating separate Class AB voltage and current gain blocks with no overall negative feedback.

The Model 725 features mil-spec ceramic circuit boards, high current copper bus bars, a power supply incorporating 4-pole capacitors and power factor correction, combined to deliver a life-like grain-free musicality of breathtaking transparency.


Machined Aluminum Chassis  
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.

Ceramic Circuit Boards
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.

Composite Circuit Architecture
Unique composite circuit architecture incorporating separate Class AB voltage and current gain blocks with no overall negative feedback, delivers 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, 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.

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 (< 1 watt consumption).

Rear Panel Remote Jack  
12V 3.5mm jack on rear panel permits amplifier power on/standby switching in remote and home theater applications.

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


Output Power  
330 watts @ 8 ohms / 650 watts @ 4 ohms

Frequency Response  
5 Hz – 350 kHz

S/N Ratio  
95 dB, ref. 1.0 watt @ 8 ohm load

Output Noise  
< 55 µv, 20 Hz – 20 kHz, unweighted

> 91 dB @ 1 kHz, 74 dB @ 20 kHz

Input Impedance  
40k ohms

THD + Noise  
0.004% @ 1 kHz, 8 ohms

Damping Factor  
> 200,  20 Hz - 20 kHz

Overall Gain (Balanced or Unbalanced)  
27 dB

Common Mode Rejection Ratio  
> 90 dB, 20 Hz – 20 kHz

Absolute Phase Non-inverting  
Pin 2 Positive

Balanced (XLR)

2 parallel binding posts

Power Consumption Idle  
85 watts

Power Consumption Standby  
1 watt

Amplifier Weight  
54 lbs. / 24.5 kg (each)

Amplifier Shipping Weight  
64 lbs. / 29 kg (each)

Overall Amplifier Dimensions (h/w/d)  
5.75” x 15.5” x 16.25” / 146mm x 394mm x 413mm (each)