For those who want to change the OPAMP:
OPAMP voltage on EF1 is +/-16.5v.
     If you ever removed the original OP275,
you will have to pay $100 repairing cost
when your EF1 need warranty service.

Original price $399, now only $ $299 (From Dec 12 to Jan 4 only)

220v version link

Opamp: OPA275
Tube: 12AU7 RCA Cleartop NOS
Frequency Response: 20-30K Hz
THD+N: less than 0.2%
S/N: more than 95dB
Input impedance: 50K Ohm
Output impedance: 2–2K Ohm headphones
Output signal strength: up to 15 Volts at 32 Ohm
Input: RCA*1
Output: 1/4 headphone jack*1
Dimension: 110mm(W)*50mm(H)*270mm(D),
or 4.33inch(W)*1.97inch (H)*10.63inch (D)
Weight: 750g (without power supply)
Acessory: 12AU7 tube, 18V AC power supply
Hand built in Shanghai, China

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Review @ techPowerUp.