ЦАПы — FiiO K11 R2R

The K11 R2R combines a desktop headphone amplifier and a DAC in one FiiO chassis, with conversion done by an in-house resistor ladder instead of a delta-sigma chip. It is offered in black, silver, red and titanium finishes and runs from an external 12 V, 2 A switching supply.

Key specs that matter

FiiO describes the converter as a fully differential true 24 bit R2R design in a four-channel layout, with two arrays of 48 precision thin-film resistors per channel, 192 resistors in total. Resistor tolerance is 0.1% with a temperature drift of 30 ppm. USB playback reaches PCM at 384 kHz and 32 bit and DSD256, the coaxial input accepts 192 kHz and 24 bit, and the optical input 96 kHz and 24 bit. Line-out SNR is at least 115 dB A-weighted, with THD+N of about 0.025% at 1 kHz. Frequency response is 20 Hz to 50 kHz with less than 1.3 dB of roll-off, or less than 0.2 dB across 20 Hz to 20 kHz. The chassis measures 147 x 133 x 32.3 mm with feet and weighs about 420 g.

Engineering and use context

Two decoding modes are selectable. NOS mode keeps the original sampling rate of the file, while OS mode upsamples everything to 384 kHz. A GD32F303RE microcontroller runs the unit, an SA9312L audio bridge with FPGA handles the USB side, and the amplifier section uses two pairs of SGM8262 op-amps with an NJW1195A electronic volume chip. Three gain levels each come with their own volume curve. The power section combines 17 low-noise LDO regulators and two DC-DC converters to derive rails of plus and minus 9 V, 8 V, plus and minus 7.5 V, plus and minus 6 V, 5.4 V, 3.3 V, 1.8 V and 1.2 V for the separate circuit blocks. A custom LCD shows status and is designed to stay on without burn-in.

Pairing

The balanced 4.4 mm output delivers at least 1300 mW per channel into 32 ohm, 520 mW into 16 ohm and 220 mW into 300 ohm, and its source impedance stays under 1.5 ohm. The 6.35 mm single-ended jack gives 660 mW per channel into 16 ohm, 460 mW into 32 ohm and 50 mW into 300 ohm, with output impedance below 1 ohm. That spread covers sensitive in-ear monitors on low gain and higher impedance dynamic headphones on high gain. The RCA sockets act as a line output for powered speakers or an integrated amplifier, or as a coaxial digital output, and a USB Type-C port connects a computer.

Alternatives

The FiiO Warmer R2R uses the same 192-resistor R2R converter in a larger chassis with four E88CC tubes and XLR outputs.