DAC | preamplifier | power amplifier
Manufacturer: Jeff Rowland Design Group
’m telling ya, there are few audio components that move music lovers and audiophiles’ hearts as much as those from Jeff Rowland. The components manufactured in Colorado Springs have a look that cannot be mistaken for anything else, and their build quality beats almost everything else in the audio world. Their distinguishing mark is their front and top panel wavy pattern finish difficult to confuse with anything else. It's an optical illusion, but an extremely convincing one. Only one other company used to have a similar, equally well-made faceplates – Enlightened Audio Design, a no longer existing American home theater specialist. Those people, now working at Noble Electronics, were fantastic in what they’re doing. Their components’ faceplates were made – no surprise there – by Jeff Rowland. Actually, Jeff Roland was the middleman as the enclosures were manufactured by a specialized firm Vertec Tool from Colorado Springs.
Attention to every last detail, almost obsessive, goes hand in hand with carefully selected design solutions, highly rated by Jeff, some of which are controversial in the audio world. To give an example, although it is not the case with the 625 under review, JR lesser amplifiers employ class D topology. And what about the 625? It is built on LME49810 integrated drivers driving discrete power transistors. On top of that, all components from this manufacturer are equipped with switching power supplies, rated very negatively by many. Linn, Chord, and now Soulution have proven that the problem was not with them but with their proper application. And, last but not least, the ubiquitous coupling transformers – every JR component sports at least a pair of them in the left and right channels, and sometimes more. They are used to couple balanced outputs or as interstage coupling. ICs abound throughout and discrete transistors are only used in the power output stage. The reason is that Jeff Rowland opts for minimalist approach – his designs employ an ultra-short signal path and minimum number of electronic components. No, this manufacturer cannot be mistaken for any other.
Albums auditioned during this review
Audio is the art of compromise – that much is clear. However, it’s important to understand that we face compromises both on the manufacturer’s side and on our own. In the classical theory of language, the manufacturer would be the sender of the message and the music lover or audiophile – whatever we call him – its receiver. But that's not all. This basic level of information exchange is overlapped with another. On the basis of the communication between the manufacturer that "programs" his products in his own way to achieve specific results, and the music lover who has his own expectations and preferences and responds in his own way to the sender’s offer, another level is applied – that of the music, with the Sender (artist, sound engineer, producer) and the Recipient (music lover, audiophile). This second pair starts with uppercase as it is the one that is most important. What’s interesting is that the arrival point is the same in both cases. The receiver/ Recipients is US. That’s why it’s so difficult to reach a consensus – the listener must define himself in the context of his expectations with regard to the music and to the medium through which the music is conveyed, that is the audio system. He has to decide whether and to what extent the music presentation can be modified – and how – and still be acceptable to him.
The sound was smooth, soft, and vivid while at the same time very deep and well differentiated. While its main dominant is the pursuit of refinement rather than perfection, the scale of differentiation was puzzling. If I were to draw analogy I would compare this presentation to that of the Harbeth M40.1 speakers. Warm and rather nice at first, after a while they turn out to be incredibly resolute. And not as selective as I would wish.
My biggest surprise was listening to the new Black Sabbath album 13. While it’s pressed as SHM-CD, the material is intended for a wide audience and hence highly compressed. First I listened to it at night, on my HiFiMAN HE-6 headphones driven from the amplifier current output, and even then I was struck by a great clarity with which Ozzy Osbourne vocals and Tony Iommi guitars were recorded and mixed. I use plural “guitars” as Tony’s guitar is overdubbed and often doubled, with lots of spatial sound effects. The tonal balance was really well set without using the proven "patent" of "wall of sound" that covers playback and recording mistakes. The sound was powerful, fleshy, but also selective. On these particular headphones drums seemed somewhat lacking, though, especially the bass drum. Rowland’s system tastefully showed what was going on. It served a very low, punchy bass, and when kettledrums appeared in the beginning of God is Dead? they were conveyed very vividly but also fast, with a rapid attack, good body and depth. Similarly, Geezer Butler’s bass guitar was super-fleshy. Now, despite adding additional elements, the sound was neither blurred nor veiled. While Mr. Fang Bien’s magnetostats had seemed made for showing attacks and fast transients which could have added some clarity to the material on the Sabbath disc, nothing like that happened. The allegedly warm Harbeths driven by the allegedly warm Rowland confirmed what I heard on the headphones, adding to that more body and fantastic volume.
Despite the impression - I'll come back to that because it's leitmotiv – of sounding warm and sweet, the Rowland system allows for such introspection. It does it casually, without being pushy. Everything I wrote is picked up along the music. It’s really addictive. The more so as with acoustic music, played without amplification, like on Clifford Brown’s Memorial or John Coltrane's A Love Supreme the presentation of bass and treble was different. At first, the cymbals and double bass seemed withdrawn. But only for a while, until something changes and we get to the place where the bass instrument is stronger, amplified by the studio walls and microphone. Then it sounds naturally and not exaggerated. But even when it’s not there we don’t hear a "hole". The sound is not dry or shallow, as if there was an “air cushion" under the midrange, containing potential information about the instrument.
The dynamics was very good, but it’s here that it’s audible something had to be "trimmed" and sacrificed. The Soulution amp is much more open and faster, giving us not only the impression of a strong attack, but also its sheer physical power right in front of us. The American system does it softer and in a more studied manner. It's this lack of spontaneity that probably needs to be taken into consideration while analyzing our needs and expectations regarding audio components.
I have no doubt that in the Sender – Receiver relationship the Jeff Rowland is excellent and has its own personal charm. It conveys the music in a very refined, thoughtful and mature way. At the same time the sender, this time with a small “s”, communicates to us the limitations of the applied solutions and decisions. If we need the ultimate dynamics and tangibility of sound, not in terms of its size and proximity but of texture clarity, today’s system will not be the best choice. In this case, such – far apart ideologically – amplifiers as the Soulution 710 (I haven’t yet heard the new 711) and the Ancient Audio Silver Grand Mono (see HERE ) will prove a better choice. If, however, we are more concerned with the color saturation, the Jeff Rowland comprising the Aeris DAC, the Corus and the 625, will be perfect. It will be a choice that’s both safe and definitive. While neither of the above machines, the Polish and the Swiss amps, can be accused of the lack of color, the American trio slightly tweaked in this regard will beat them easily.
Jeff Rowland is best known for its amplifiers (and preamplifiers). Since computer related sources came into play, DACs have also become increasingly important. The AERIS DAC is the only such product offered by this manufacturer. It was part of the system under review, together with other Rowland components – the Corus preamplifier and the 625 power amplifier. That was how I conducted auditions that had the character of an A/B/A comparison, with the A and B known. The point of reference was my reference system. The Jeff components were coupled with the Acoustic Revive cables from the System II (see the description of the reference system). The DAC was fed digital signal off the Ancient Audio Lektor Air V-edition sporting the Philips CD-Pro2LF transport via the Oyaide DB-510 digital interconnect with BNC connectors. Although the DAC came equipped with get an RCA adapter that makes possible using an RCA to RCA digital cable, I wanted to avoid that. I used a reverse adapter of this type (from Stereovox) on the CD player side. USB connection was via the Acoustic Revive USB-5.0PL (5 m) cable from my HP Pavilion dv7 laptop (SSD 128GB + HDD 320GB, Windows 8 Pro x64) running the latest version of JPLAY audio player. AERIS USB input is limited to 96 kHz. To play 176.4 kHz and 192 kHz files I had to use the USB-S/PDIF M2TECH hiFace EVO external converter with the EVO battery supply (see HERE).
Jeff Rowland Design Group made build quality its own personal religion. Jeff Roland components are housed in very expensive, sophisticated enclosures which are precision machined from a single block of 6061-T6 aircraft grade aluminum and sport very thick, unique faceplates. The latter are silver finished in a special laser process to give their surface a wavy look. While it may sound a tad cheesy, their appearance is nothing like that.
DAC is the smallest unit of the three. The low front fascia sports a row of buttons and LEDs in different colors.
Let’s stop, however, at the front panel. We see here several groups of buttons and LEDs. The first button group comprises an input selector to choose between TOSLINK, one of the two BNC and USB. The first three receive signal up to 24/192; the USB port is limited to 96 kHz. This eliminates the need for driver installation but won’t let us play 192 kHz audio files. To do that, we need an external USB-S/PDIF converter connected to one of the BNC inputs. Blue LEDs indicate the input selected. Next to them, we have a standby button with an orange LED. It is followed by a row of green LEDs indicating input signal sampling frequency. Below are two LEDs that signal establishing a link with the source and non-standard signal sampling rates, respectively. Next we have a mute button with a red LED and two volume control buttons with blue LEDs. The Aeris is capable to drive a power amplifier directly, as its maximum output voltage is 7 V. When using a preamplifier, the DAC output level needs to be attenuated to avoid input overload. The manufacturer claims that this doesn’t degrade the sound quality as the Aeris volume control is neither purely analog nor digital. Instead, it is implemented by varying the reference current in the DAC chip.
DAC’s interior explains the unit’s substantial weight – to pick it up is like lifting a metal block. That is not far off the mark as the chassis is machined from a solid block of aluminum with milled out pockets housing electronic circuits and cables. Electronic circuit is mounted on a small PCB. The USB input is on an old TAS1020 chip, well-known for years. But this is a special that was programmed by Gordon Rankin from Wavelength Audio. It works in an asynchronous mode and is known for its excellent sound. The S/PDIF inputs feature coupling transformers. The signal from the selected input is sent to a Xilinx Spartan DSP with an asynchronous buffer for jitter reduction. Next to it are two small crystal oscillators, separately for 44.1 kHz and 48 kHz based sample rates.
The DAC comes with a remote control. It's a beautiful, heavy chunk of machined aluminum sporting small control buttons. IR receiver is placed rather unconventionally under the unit’s bottom panel and is visible from the front. The remote duplicates the control functions available from the front panel.
The preamplifier is larger than the DAC but still not large. Unlike the DAC, its user interface features a large, white VFD display. Control buttons are placed below and include input and record source selectors, menu, display off and mute. Next there is a classic, if small, volume control knob, which for me is far more convenient to use than buttons. The really nice and clear display presents us with lots of information. Large digits show volume level in 0.5 dB increments. An adjacent bar graph displays channel balance while the currently selected input is shown above. The input names can be changed. We also get information about which source is routed to the record output.
The Corus chassis is a machined block of aluminum. The whole interior is milled out, leaving only thick screen walls between the input and gain sections. The latter is truly unique and features an ultra-short signal path. I could only identify two TI Burr-Brown OPA1632 opamps and three Burr Brown PGA 23201 volume control chips – one for each of the line outputs, A and B, and the record output (yes, its level can be adjusted separately). The signal path also features Lundahl coupling transformers in the input and output stages. Input switching is logic controlled. That's it. This must be the most minimalist active preamplifier I have yet seen.
Nothing focuses Jeff Rowland’s obsessions and "inner demons" as much as its power amplifiers. Once battery powered (yes!), they now feature sophisticated multi-stage switching power supplies. Their chassis is milled from a single aluminum billet, with characteristic heat sinks. The latter are needed to cool down 625’s six pairs of Sanken Darlington modules (STD03N + P) in push-pull configuration per channel. Premium circuit components include ultra-precision Dale resistors. Ground lines incorporate gold plated copper bus bars. The input stage features Lundahl coupling transformers as the amplifier only accepts a balanced signal. Interestingly, right in the center, four LME49810 integrated audio power amps from National Semiconductors – two per channel due to a balanced topology – are mounted to a small section of the chassis. These are designed to work as power amp drivers and when used with a discrete output stage can deliver up to 300 W at 4 Ω. Mystery solved… The gain section is assembled on a large circuit board. Underneath, separated by a thick screen, is a power supply board. Everything is beautifully assembled. I’ve already mentioned the inputs on single Neutrik XLR connectors. Let’s add to it that the speaker outputs are two pairs of superb Cardas speaker terminals designed for spade connectors.
- Turntable: AVID HIFI Acutus SP [Custom Version]
- Cartridges: Miyajima Laboratory KANSUI, review HERE | Miyajima Laboratory SHILABE, review HERE | Miyajima Laboratory ZERO (mono) | Denon DL-103SA, review HERE
- Phono stage: RCM Audio Sensor Prelude IC, review HERE
- Compact Disc Player: Ancient Audio AIR V-edition, review HERE
- Multiformat Player: Cambridge Audio Azur 752BD
- Line Preamplifier: Polaris III [Custom Version] + AC Regenerator, regular version review (in Polish) HERE
- Power amplifier: Soulution 710
- Integrated Amplifier: Leben CS300XS Custom Version, review HERE
- Stand mount Loudspeakers: Harbeth M40.1 Domestic, review HERE
- Stands for Harbeths: Acoustic Revive Custom Series Loudspeaker Stands
- Real-Sound Processor: SPEC RSP-101/GL
- Integrated Amplifier/Headphone amplifier: Leben CS300XS Custom Version, review HERE
- Headphones: HIFIMAN HE-6, review HERE | HIFIMAN HE-500, review HERE | HIFIMAN HE-300, review HERE | Sennheiser HD800 | AKG K701, review (in Polish) HERE | Ultrasone PROLine 2500, Beyerdynamic DT-990 Pro, version 600 - reviews (in Polish): HERE, HERE, HERE
- Headphone Stands: Klutz Design CanCans (x 3), review (in Polish) HERE
- Headphone Cables: Entreq Konstantin 2010/Sennheiser HD800/HIFIMAN HE-500, review HERE
- Interconnects: Acrolink Mexcel 7N-DA6300, review HERE | preamplifier-power amplifier: Acrolink 8N-A2080III Evo, review HERE
- Loudspeaker Cables: Tara Labs Omega Onyx, review (in Polish) HERE
- Interconnects: Acoustic Revive RCA-1.0PA | XLR-1.0PA II
- Loudspeaker Cables: Acoustic Revive SPC-PA
- Power Cables: Acrolink Mexcel 7N-PC9300, all system, review HERE
- Power Distributor: Acoustic Revive RTP-4eu Ultimate, review HERE
- Power Line: fuse – power cable Oyaide Tunami Nigo (6m) – wall sockets 3 x Furutech FT-SWS (R)
- Power Cables: Harmonix X-DC350M2R Improved-Version, review (in Polish) HERE | Oyaide GPX-R (x 4 ), review HERE
- Power Distributor: Oyaide MTS-4e, review HERE
- Portable Player: HIFIMAN HM-801
- USB Cables: Acoustic Revive USB-1.0SP (1 m) | Acoustic Revive USB-5.0PL (5 m), review HERE
- LAN Cables: Acoustic Revive LAN-1.0 PA (kable ) | RLI-1 (filtry), review HERE
- Router: Liksys WAG320N
- NAS: Synology DS410j/8 TB
- Stolik: SolidBase IV Custom, read HERE/all system
- Anti-vibration Platforms: Acoustic Revive RAF-48H, review HERE/digital sources | Pro Audio Bono [Custom Version]/headphone amplifier/integrated amplifier, review HERE | Acoustic Revive RST-38H/loudspeakers under review/stands for loudspeakers under review
- Anti-vibration Feets: Franc Audio Accessories Ceramic Disc/ CD Player/Ayon Polaris II Power Supply /products under review, review HERE | Finite Elemente CeraPuc/ products under review, review HERE | Audio Replas OPT-30HG-SC/PL HR Quartz, review HERE
- Anti-vibration accsories: Audio Replas CNS-7000SZ/power cable, review HERE
- Quartz Isolators: Acoustic Revive RIQ-5010/CP-4
- FM Radio: Tivoli Audio Model One