Tor Audio writes: “In the heart of the “David” Tube DAC is the Texas Instruments PCM5102A converter, that is partnered with the toroidal audio transformer.”

“We’ve decided to use such exotic things as toroidal audio transformers. This is the most complicated part, toroidal transformers take approximately 80% of the time required for the manufacturing of the device, but they sound great. The core of toroidal transformer is manufactured by winding a long steel strip, just as a film on the tape reel.  The toroidal core is free of rips, joints and air-gaps. Due to all these benefits, the sound quality of toroidal transformers is far superior.

Boost Stage is assembled on a double triode 6N8S (analogue 6SN7), with the lowest internal resistance, which has a positive effect on the quality of sound.
“David” USB input runs on Mac OS X 10.5 Leopard or later and is Core Audio compliant. On a Windows, “David” runs on Windows XP, 7, 8, 10 (XMOS audio driver). 
And it is also fully compliant with Linux.
– Boost Stage: Wima, Vishay, Elna Silmic II.
– Power Stage: Cornell Dubilier Electronics, toroidal power transformer
Reliability. All the details of the circuit are selected in such a way that the amplifier has worked for decades with no repair and maintenance.
► The price is 700 USD
► WARRANTY – 10 years
Technical Specifications
– DAC: TI PCM5102A, USB: XMOS (32bit / 384K)
– Output: RCA, headphone 1/4 Jack (Recommended load impedance: 25 ohm – 600 ohm)
– Frequency response (Digital): 20 Hz – 20 kHz
– Frequency response (Analog): 10 Hz – 125 Khz
– Tube: 6N8S (analogue 6SN7) (not hybrid)
– “A” mode.
– Rectifier: valve tube 6c5s (analogue 6X5GT)
– Toroidal Audio Transformers
– Power input: 100-127V or 220-240V (toroidal power trans.)
– Handmade