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Let’s return to the front panel with its several groups of buttons and LEDs. The first group comprises an input selector to choose between optical, two BNC and USB. The first three process 24/192; USB is limited to 96kHz. This eliminates the need for driver installations but won’t let us play 176.4/192 kHz files. For that we need an external USB-to-S/PDIF converter connected to one of the BNC inputs [the Audiophilleo 2 would be ideal as it mounts directly to the BNC without a cable – Ed]. Blue LEDs indicate the selected input. Next to them we have a standby button with an orange LED followed by a row of green LEDs indicating the incoming sampling rate. Below are two LEDs that signal clock lock and non-standard sample rates respectively. Next we have a mute button with a red LED and two volume control buttons with blue LEDs. The Aeris can drive a power amplifier directly with its stout 7V max. When using a preamplifier this needs to be attenuated to avoid input overload. JRDS claim this won’t degrade sound quality as the Aeris volume control is neither purely analog nor digital. Instead it is implemented by varying the reference current in the converter chip.

The rear panel confirms perfect enclosure design. The analog Rhodium-plated copper connectors from Cardas use Teflon dielectric and look superb. The BNC connectors are gold plated. Only the USB port looks ordinary. Next to it is a multi-pin Neutrik SC8 connector for the external power supply umbilical housed in a chassis as solid as that of the DAC. This turns out to be a switching power supply with two separate supplies for digital and analog. In fact all three components are SMPS powered.

The DAC’s interior explains its substantial weight. To pick it up is like lifting a metal brick. That's not far off the mark. The chassis is milled from solid aluminium with discrete pockets for circuits and hookup cabling. The main circuit mounts to a small PCB. The USB input is a vintage TAS1020 transceiver programmed by Gordon Rankin of Wavelength Audio to work in asynchronous mode. The S/PDIF inputs feature isolation transformers. The selected input signal hits a Xilinx Spartan DSP chip with asynchronous buffer for jitter reduction. Next to it are two small crystal oscillators for the 44.1kHz and 48kHz sample rate families.

From there we get to the single AD1853 converter chip from Analog Devices. The entire analog circuit is built on 6 x L49990 opamps per channel. These are ultra-low distortion low-noise high-slew-rate Overture E-Series operational amplifiers. The output is relay-switched, the XLR buffered by Lundahl transformers. The hookup cable to the outputs is a short length of kabelkami. The DAC comes with a remote control, a beautiful heavy chunk of machined aluminum sporting small control buttons. The 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 fascia.

Corus. 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 knob which to me is far more convenient than push buttons. The very nice clear display presents us with much information. Large digits show the volume level in 0.5dB increments. An adjacent bar graph displays channel balance whilst the currently selected input shows above. Input names can be assigned. We also get information about which source is routed to the variable record output.

The rear panel looks very impressive again. It sports ample inputs by way of 4 x XLR and 2 x RCA. Unfortunately the XLR connectors are not Cardas but classic Neutriks with gold-plated pins. The inputs are complemented by two each XLR and RCA plus XLR and RCA rec outs. In the center are two multi-pin sockets to the external power supply. The latter is as superbly finished as the DAC’s PSU except that it sports two umbilical. That's because it actually houses two separate supplies for the left and right channels. And there's one little connector in the bottom. Unlike with the DAC, an IR receiver in its own metal housing must be connected here.

The Corus chassis is again milled from solid aluminum. Here the entire interior is milled out, leaving only thick shielding walls between the input and gain sections. The latter is truly unique and features an ultra-short signal path. I could only identify 2 x TI Burr-Brown OPA1632 opamps and 3 x Burr Brown PGA 23201 volume chips, one for each of the line outputs, one for the record output whose level can be adjusted separately. The signal path features Lundahl coupling transformers at both the inputs and outputs. Input switching is logic controlled. That's it. This must be the most minimalist active preamplifier I have seen yet.

625. Nothing focuses Jeff Rowland’s obsessions and 'inner demons' like power amplifiers. Once battery powered they now feature sophisticated multi-stage switching power supplies. Their chassis is milled from aluminium billet with trademark heat sinks. The latter cool down six pairs of Sanken Darlington STD03N+P modules 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 balanced signal. Interestingly right in the center four LME49810 power ICs from National Semiconductor—two per channel due to the balanced topology—mount to a small section of the chassis. These work as power amp drivers. When used with a discrete output stage they can deliver up to 300w into 4Ω. The gain section assembles on a large circuit board. Separated by a thick screen, the power supply board sits beneath it. Everything is beautifully assembled. I already mentioned the inputs on single Neutrik XLR. The speaker terminals are two pairs of superb Cardas designed exclusively for spades. The amplifier sits on three small ball footers. The entire finishing work is spectacular – insanely good.
opinia @ highfidelity.pl
Jeff Rowland Design Group website