This review page is supported in part by the sponsors whose ad banners are displayed below
"This is what I would say should someone with a lot of patience ask for the difference between udc1/spa1 and u:c:a.
The u:c:a is essentially an udc1 where the signal is made single-ended in the first amplifying stage. A selected blue Alps RK27 potentiometer located between first stage and following buffer stage enables volume control. The udc1 lacks this volume control because the signal is balanced from beginning to end and thus a 4-gang potentiometer would have had to be used. Since the common mode rejection ratio (CMRR) suffers enormously from differences in the ganged operation, a stepped resistor attenuator is a far better choice. That’s exactly what you will find inside the spa1.
"Unfortunately these gold-plated switches are very costly. The Swiss Elma arrangement employed in the spa1 has a wholesale price of around €150 plus the cost of sixty (60!) precision resistors. Obviously this was not the way to go for the u:c:a. The use of a single enclosure with a single power supply enables us to offer a competitive price for the new USB-coax amplifier even though looking inside the box you won’t see any signs of savings.
"You will notice the same high-quality semiconductors in the digital and analogue sections as well as for voltage regulation. Naturally the same applies to all passive components.
"In detail. The USB input uses the M2tech OEM printed circuit board without voltage regulators. All the sonically important peripheral circuits were developed by us. The mechanical construction consisting of a daughter board enables us to in the future offer other platforms as plug-in replacements. A board using the XMOS XS1-L1 chip for those wanting native Mac support is in the pipeline already. There may be a small extra charge for that option. An S/PDIF receiver with very high jitter rejection is built in to further enhance flexibility. Again we see complete galvanic input isolation to eliminate the possibility of ground loops and thus get rid of any noise pick-up. The WM8804 chip from Wolfson Semiconductor accepts sample rates from 32 to 192kHz up to 24 bits.
OEM hiFace with Xilinx FPGA, Cypress Semiconductor transceiver and discrete clocks for 44.1/48kHz multiples
"The DAC section consists of the TI/Burr Brown PCM1794A with upfront TI/BB4192 sample-rate converter.
D/A conversion chip, separate sample-rate converter
"Since the PCM1794A is a current output chip without inbuilt operational amplifiers of uncertain quality, we need I/V conversion. This is done with an ultra low-noise bipolar transistor and a pair of precision-matched resistors. In contrast to our CDP3E CD player and udc1, the signal is made single-ended at this stage.
The critical amplifying stage following the potentiometer is build around a matched very low-noise JFet.
Output stage
"There are no opamps or other chip amplifiers. Everything is constructed old school with discrete components. This stage easily drives 32-ohm headphones with a max continuous power of 500mW as well as any power amp connected to the rear RCA connectors. The signal path is DC-coupled throughout so no coupling caps were necessary. A dual medium-power 1A transistor from Zetex is used for the output stage as well as for other tasks."
Even without opening the u:c:a there are signs of extremism for this class. All type face is engraved, not silk-screened. It'll never rub off. The chunky volume knob sports a precise 0dB marking to indicate where the standard-DAC 2V output sits (max = 4V, total range spans -80 to +6dB). Who else even bothers with letting you know? The S/PDIF input isn't a customary coax. It's a higher-performing BNC. The type beneath it reads '75 ohms, 0.5Vss'. The equivalent beneath the USB input says '192kHz - 24 bit'. Who needs an owner's manual? You still get a nice one. You really only need it for the download link to the M2Tech async USB drivers (rumors have it that the 32bit/384kHz Young driver sounds better than the standard hiFace driver).
Finally the clam-shall aluminum extrusion is thicker than common. It makes for a stouter less ringy enclosure. Anyone familiar with the competition would in all this recognize indicators of minimalist perfectionism. The 'handmade in Germany' engraving underscores that impression. Ivo Linnenberg's 2-in-1 component really shows no evidence of cost cutting or compromise. The first unit dispatched exhibited some S/PDIF signal-lock issues which a quickly revised second unit successfully remedied. This sidebar documents that little detour.
