{"id":9568,"date":"2016-12-26T22:09:13","date_gmt":"2016-12-26T20:09:13","guid":{"rendered":"http:\/\/www.hifi-advice.com\/blog\/?page_id=9568"},"modified":"2022-12-25T11:58:09","modified_gmt":"2022-12-25T09:58:09","slug":"jrdg-company-special-model-725725-s2-and-625625-s2","status":"publish","type":"page","link":"https:\/\/www.hifi-advice.com\/blog\/jeff-rowland-power-amplifiers\/jrdg-company-special-model-725725-s2-and-625625-s2\/","title":{"rendered":"JRDG Company Special – Model 725\/725 s2 and 625\/625 s2"},"content":{"rendered":"

Model\u00a0625\u00a0(stereo)<\/h2>\n

2011-2015<\/strong>
\nRetail price in 2013\u00a0in the Netherlands 17.250\u00a0euro<\/p>\n

Model\u00a0625 s2\u00a0(stereo)<\/h2>\n

2015-2022<\/strong>
\nRetail price in 2016 in the Netherlands 21.000\u00a0euro<\/p>\n

Also used in Marten Mingus Quintet review<\/a>
\nAlso used in Analog Domain review<\/a><\/p>\n

\"rowland-625_stereo_compressed_550pix\"<\/p>\n

Model\u00a0725\u00a0(mono)<\/h2>\n

2012-2015<\/strong>
\nRetail price in 2013\u00a0in the Netherlands 35.500 euro<\/p>\n

Extensive Review<\/a><\/p>\n

Model\u00a0725 s2\u00a0(mono)<\/h2>\n

2016-2018<\/strong>
\nRetail price in 2016\u00a0in the Netherlands\u00a045.000 euro<\/p>\n

\"rowland-725-cp-img_9973_550pix\"<\/p>\n

Back to class A\/B<\/strong><\/p>\n

For the higher-end models, Rowland has returned to class A\/B! Power supplies are a smart implementation of switched power, PFC and big capacitors.<\/p>\n

Precision machined from a single block of non-resonant aircraft-grade aluminum, the Model 625 features a unique composite circuit architecture incorporating separate Class AB voltage and current gain blocks with no overall negative feedback and virtually free of internal and external EMI field contamination and mechanical vibration.<\/p>\n

According to the manufacturer, the Model 625 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.<\/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 has phased out the 925, judging from its absence from the 2012 brochure. Too energy-consuming? Not compliant with EU regulations? Who will tell? Fact is, the 825 became available again (I even heard a pair at a demo) in 2013.<\/p>\n

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.<\/p>\n

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.<\/p>\n

625\/725 and 825\/925 differences<\/b><\/p>\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

Ron Gaston information<\/strong><\/p>\n

Ron, the proprietor of Black Forest Audio in Black Forest (CO), long time Rowland dealer, has extensive experience with every Rowland amp since the original M7. Here is what Ron wrote on a forum about M8 and M9 versus M825, M925, and M625:<\/em><\/p>\n

“The Model 8\/9 amps are big, rich and earthy in presentation. They are not, however, a match for the 825\/925 in soundstage, detail or palpable realism. They seem downright sluggish in comparison. I believe [even] the 625 to be superior in nearly every respect to these older, very great amps.” Ron further explains that only in the bottom end authority M9 variants do outperform the little M625.<\/em><\/p>\n

HFA<\/strong><\/p>\n

While I can imagine that the big model 9 sounds a little slower, I can testify that the model 6’s absolutely do not sound slow at all. In a direct comparison with the 725’s, the sixes seem to be just as detailed and refined as the later models, but they are just more relaxed with it and don’t throw the stage in your face. I do agree that compared to the sixes, the 725s sound more upbeat and lively, and they’re also more powerful. Read the full 725 review here<\/a>.<\/p>\n

Series 2<\/strong><\/p>\n

Apparently, the 625 was brought closer to the performance of the 725, allegedly making the 625 s2 sound almost as good as the 725. Actually, having heard both the 625 s2 and the 725’s, I feel that they sound quite different: the 625S2 warmer and smoother and the 725’s cleaner and drier.<\/p>\n

The same was done later for the 725 apparently\u00a0acquiring some of the advancements learned with the model 925. However, we may never know as the 725(S2) has been taken out of production early 2018.<\/p>\n

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.<\/p>\n

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.<\/p>\n

625\/725 spurious noise when power cycling – not with the 925<\/strong><\/div>\n

Unlike M725 and M625, which have a mild propensity to emitting very soft, spurious HF noise from the speakers whenever power is cycled on\/off (not when switching to\/from standby), M925 are apparently extremely quiet. A forum post reads: “When the front-mounted momentary contact switch is operated to turn the amps to full power, there is only the internal “Klump” from a relay switch, followed after a second or two by an almost inaudible “tick” from the speakers. When the power button is operated again to place the amps back on standby, there is no noise at all from the speakers or from the amps”.<\/p>\n

\n

Model 625 Pictures<\/h2>\n

\"rowland-625-front-l_550pix\"<\/p>\n

\"rowland-625-rear-l_550pix\"<\/p>\n

\"rowland-aeris-corus-725_550pix\"<\/p>\n

Beautiful stack of Aeris, Corus, 725’s<\/p>\n

\"rowland-corus-and-model-625_550pix\"<\/p>\n

625 With Corus on top<\/p>\n

\"rowland-625_interior_a-side_550pix\"<\/p>\n

625 inside – top side<\/p>\n

\"rowland-625_interior_b-side_550pix\"<\/p>\n

625 inside – bottom side<\/p>\n

Model 725 Pictures<\/h2>\n

\"rowland-725-cp-img_9973_550pix\"<\/p>\n

\"rowland-725-aeris-en-psu-img_0701cc_550pix\"<\/p>\n

\"JRDG_m725_550pix<\/p>\n

725’s during a HFA review<\/p>\n

\"rowland-725-back_550pix\"<\/p>\n

Double speaker terminals for easy bi-wiring<\/p>\n

\"JRDG_m725_550pix<\/p>\n

\"rowland-625-inside-l_rowland_12_489pix\"<\/p>\n

\"rowland-625-inside-j_rowland_12_a_350pix\"<\/p>\n

625 inside – top side<\/p>\n

\"rowland-625-inside-onderl_rowland_13_512pix\"<\/p>\n

625 inside – bottom side<\/p>\n

\n

Model 625 Features<\/h2>\n

Machined Aluminum Chassis
\nPrecision-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.<\/p>\n

Composite Circuit Architecture
\nUnique 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.<\/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 Current Copper Bus-bars
\nHigh current, dual polarity, ultra low impedance copper bus-bars distrubute 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.<\/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

Transformer-Coupling and Isolation
\nTransformer 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.<\/p>\n

Power Factor Correction
\nPower Factor Correction (PFC) in the power supply reduces AC line harmonic noise pollution and increases AC line power utilization to 99%.<\/p>\n

High-Efficiency Switch-Mode Power Supply
\nHighly 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.<\/p>\n

Dual-Position Speaker Terminals
\nDual CE approved speaker output terminals, in both horizontal and vertical orientation, 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 (< 1 watt consumption).<\/p>\n

Rear Panel Remote Jack
\n12V 3.5mm jack 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 625 Technical Specifications<\/h2>\n

Stereo power amp<\/p>\n

Output Power<\/strong>
\n300 watts @ 8 ohms
\n550 watts @ 4 ohms<\/p>\n

Frequency Response<\/strong>
\n5 Hz \u2013 350 kHz<\/p>\n

S\/N Ratio<\/strong>
\n95 dB, ref. 1.0 watt @ 8 ohm load<\/p>\n

Output Noise<\/strong>
\n< 55 \u00ecv, 20 Hz \u2013 20 kHz, unweighted<\/p>\n

Crosstalk<\/strong>
\n> 91 dB @ 1 kHz, 74 dB @ 20 kHz<\/p>\n

Input Impedance<\/strong>
\n10k ohms<\/p>\n

THD + Noise<\/strong>
\n0.005% @ 1 kHz, 8 ohms<\/p>\n

Damping Factor<\/strong>
\n> 200, 20 Hz – 20 kHz<\/p>\n

Overall Gain (Balanced or Unbalanced)<\/strong>
\n27 dB<\/p>\n

Common Mode Rejection Ratio<\/strong>
\n> 90 dB, 20 Hz \u2013 20 kHz<\/p>\n

Absolute Phase<\/strong>
\nNon-inverting Pin 2 Positive<\/p>\n

Inputs<\/strong>
\n1 pair balanced (XLR)<\/p>\n

Outputs<\/strong>
\n2 pair parallel binding posts per channel<\/p>\n

Power Consumption<\/strong>
\nIdle 100 watts
\nStandby 1 watt<\/p>\n

Amplifier Weight<\/strong>
\n54 lbs. \/ 24.5 kg<\/p>\n

Amplifier Shipping Weight<\/strong>
\n64 lbs. \/ 29 kg<\/p>\n

Overall Amplifier Dimensions (h\/w\/d)<\/strong>
\n5.75\u201d x 15.5\u201d x 16.25\u201d \/ 146mm x 394mm x 413mm<\/p>\n

\n

Model 725 Features<\/h2>\n

Machined Aluminum Chassis
\nPrecision-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.<\/p>\n

Ceramic Circuit Boards
\nAll audio circuits are implemented on mil-spec, multi-layer, low dielectric constant, Rogers\u2122 ultra-rigid ceramic circuit board substrate for extremely low energy retention and absorption. Large low impedance ground plane areas for extended internal star-grounding.<\/p>\n

Composite Circuit Architecture
\nUnique 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.<\/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 Current Copper Bus-bars
\nHigh 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.<\/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

Transformer-Coupling and Isolation
\nTransformer 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.<\/p>\n

Power Factor Correction
\nPower Factor Correction (PFC) in the power supply reduces AC line harmonic noise pollution and increases AC line power utilization to 99%.<\/p>\n

High-Efficiency Switch-Mode Power Supply
\nHighly 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.<\/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 (< 1 watt consumption).<\/p>\n

Rear Panel Remote Jack
\n12V 3.5mm jack 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 725 Technical Specifications<\/h2>\n

Mono power amp<\/p>\n

Output Power<\/strong>
\n330 watts @ 8 ohms
\n650 watts @ 4 ohms<\/p>\n

Frequency Response<\/strong>
\n5 Hz \u2013 350 kHz<\/p>\n

S\/N Ratio<\/strong>
\n95 dB, ref. 1.0 watt @ 8 ohm load<\/p>\n

Output Noise<\/strong>
\n< 55 \u00b5v, 20 Hz \u2013 20 kHz, unweighted<\/p>\n

Crosstalk<\/strong>
\n> 91 dB @ 1 kHz, 74 dB @ 20 kHz<\/p>\n

Input Impedance<\/strong>
\n40k ohms<\/p>\n

THD + Noise<\/strong>
\n0.004% @ 1 kHz, 8 ohms<\/p>\n

Damping Factor<\/strong>
\n> 200, 20 Hz – 20 kHz<\/p>\n

Overall Gain (Balanced or Unbalanced)<\/strong>
\n27 dB<\/p>\n

Common Mode Rejection Ratio<\/strong>
\n> 90 dB, 20 Hz \u2013 20 kHz<\/p>\n

Absolute Phase<\/strong>
\nNon-inverting Pin 2 Positive<\/p>\n

Inputs Balanced (XLR)<\/strong>
\nOutputs 2 parallel binding posts<\/p>\n

Power Consumption<\/strong>
\nIdle 85 watts
\nStandby 1 watt<\/p>\n

Amplifier Weight<\/strong>
\n54 lbs. \/ 24.5 kg (each)<\/p>\n

Amplifier Shipping Weight<\/strong>
\n64 lbs. \/ 29 kg (each)<\/p>\n

Overall Amplifier Dimensions (h\/w\/d)<\/strong>
\n5.75\u201d x 15.5\u201d x 16.25\u201d \/ 146mm x 394mm x 413mm (each)<\/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\u00a0625\u00a0(stereo) 2011-2015 Retail price in 2013\u00a0in the Netherlands 17.250\u00a0euro Model\u00a0625 s2\u00a0(stereo) 2015-2022 Retail price in 2016 in the Netherlands 21.000\u00a0euro Also used in Marten Mingus Quintet review Also used in Analog Domain review Model\u00a0725\u00a0(mono) 2012-2015 Retail price in 2013\u00a0in the Netherlands 35.500 euro Extensive Review Model\u00a0725 s2\u00a0(mono) 2016-2018 Retail price in 2016\u00a0in the Netherlands\u00a045.000 euro […]<\/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-9568","page","type-page","status-publish","hentry"],"_links":{"self":[{"href":"https:\/\/www.hifi-advice.com\/blog\/wp-json\/wp\/v2\/pages\/9568","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=9568"}],"version-history":[{"count":16,"href":"https:\/\/www.hifi-advice.com\/blog\/wp-json\/wp\/v2\/pages\/9568\/revisions"}],"predecessor-version":[{"id":33942,"href":"https:\/\/www.hifi-advice.com\/blog\/wp-json\/wp\/v2\/pages\/9568\/revisions\/33942"}],"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=9568"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}