Unison Research SH Tube Headphone Amplifier

Unison Research Tube Headphone Amplifier with cherry faceplate.  New retail $1700.  

The SH is fitted with a linear circuit that produces low negative feedback and an output voltage which is capable of driving a wide range of headphones. 

The input stage of the SH uses an ECC83 valve while the output uses an EL84, the latter being used as it’s capable of driving the output transformer with “optimal electrical and sound character”.

There are two headphone outputs on the SH, connected in parallel and each with their own EL84 valve and a sensitivity switch to accommodate a range of headphone types. 

Any line-level source can be connected to the unbalanced RCA input but the SH can also support audio files up to 384kHz PCM and DSD 128 thanks to an asynchronous USB input and integrated DAC.

Maximum output voltage (THD 1%):output "High sensibility" 0.5 V/150 ohm, 0.45 V/33 ohm, 0.4 V/10 ohm output "Low sensibility" 1.5 V/150 ohm, 1.2 V/33 ohm, 0.65 V/10 ohmFrequency Response:-0.1 dB @ 10Hz / 3-dB @ 50 kHz (output "Low sensibility", 33 ohm load)Input impedance:20 kohm // 100 pFSensibility:0.67 V in/ 0.33 V out (output "High sensibility", 10 ohm load) 0.67 V in / 1 V out (output "Low sensibility",33 ohm load)Input stage:Pure Class A, ECC83/12AX7Output stage:Class A, 2 EL84 triode connectedInputs:1 line RCA, 1 USBOutputs:2 (parallel connected)Feedback factor:16 dBTHD:< 0.2% @ 1kHz, 0.5V,Absorption:45 WDimension:22,5 cm x 12,6 cm x 32,2 cmWeight:6 kg

USB DAC SPECIFICATION

• Asynchronous USB interface compliant to USB 2.0 Audio Class
• Accepts PCM up to 384kHz and DSD up to 128x
• Resolution up to 32 bits
• Last generation ESS Sabre DAC with jitter eliminator circuit
• Galvanic isolation between USB interface and conversion circuit
• Low phase noise clocks which reside in the “clean” supply domain to preserve low jitter performance
• 110dB SNR (@ 1kHz, “A” weighted, 192kHZ) 0.008% THD+N (@ 1kHz, -3dBFS)