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Headphones amplifiers — AudioValve Eartube Mark II
Description, images, technical data and specifications
AudioValve Eartube Mark II
Image source — © AudioValve
The Eartube Mark II is a valve headphone amplifier from AudioValve, which AudioValve presents as a small-power amplifier built specifically to drive headphones and as a logical development of the company's earlier Eartube models. Only valves sit in the signal path, with solid-state parts limited to the voltage supply, and a Mark II USB variant is also built.
Key specs that matter
Output is 2 x 3.5 W into 100 ohm, and the amplifier accepts headphones rated from 8 up to 200 ohm. AudioValve lists a power bandwidth of 8 Hz to 80,000 Hz, a signal-to-noise ratio of 100 dB and channel separation of 70 dB. Two pairs of gold-plated RCA inputs have different gain - 14.5 dB on input 1 and 21.5 dB on input 2 - and both present 47 kOhm. Two Neutrik 6.3 mm jacks on the front panel let two listeners plug in at once. Power consumption is 100 VA, and mains versions for 100 V and 245 V are built. The case measures 38 cm wide, 26 cm deep and 12 cm high, and the unit weighs 10 kg.
Engineering and use context
Three 6N3P double triodes form the input stage, and a pair of QQE 03/12 power tetrodes in the long-life Siemens military version drive the output in push-pull. Operation is class A, with bias regulated automatically, so no manual bias adjustment is needed when valves are changed, and AudioValve names GU17, RS1023 and 6360 as equivalents for the output tubes. A toroidal transformer feeds the supply, and all parts sit on one two-layer circuit board. A switchable bass crossfeed filter mixes part of the left channel into the right and vice versa, which AudioValve links to lower listening fatigue on headphones. Volume is set with a large Alps logarithmic potentiometer, and a smaller knob beside it trims balance by up to 2 dB either way. A rocker switch on the front picks the source. After switch-on the unit needs about 30 seconds to become ready, and stereo level meters on the front light up. The metal case, in black or silver, also shields the circuit from outside interference. The USB version adds a player section for USB sticks, SD cards and FM with its own remote.
Pairing
With its wide load range, the Eartube handles most dynamic headphones, while the higher-gain input suits sources with a modest output level. AudioValve adds that the amplifier can also drive loudspeakers. Two gold-plated XLR sockets on the rear carry a volume-controlled signal, so the Eartube can work as a preamplifier for separate power amplifiers, with only pin 2 wired as the hot phase.
Alternatives
The AudioValve RKV Mark II is an output-transformerless headphone amplifier on four 6F5P valves, rated at 8 W per channel into 220 ohm.
Key specs that matter
Output is 2 x 3.5 W into 100 ohm, and the amplifier accepts headphones rated from 8 up to 200 ohm. AudioValve lists a power bandwidth of 8 Hz to 80,000 Hz, a signal-to-noise ratio of 100 dB and channel separation of 70 dB. Two pairs of gold-plated RCA inputs have different gain - 14.5 dB on input 1 and 21.5 dB on input 2 - and both present 47 kOhm. Two Neutrik 6.3 mm jacks on the front panel let two listeners plug in at once. Power consumption is 100 VA, and mains versions for 100 V and 245 V are built. The case measures 38 cm wide, 26 cm deep and 12 cm high, and the unit weighs 10 kg.
Engineering and use context
Three 6N3P double triodes form the input stage, and a pair of QQE 03/12 power tetrodes in the long-life Siemens military version drive the output in push-pull. Operation is class A, with bias regulated automatically, so no manual bias adjustment is needed when valves are changed, and AudioValve names GU17, RS1023 and 6360 as equivalents for the output tubes. A toroidal transformer feeds the supply, and all parts sit on one two-layer circuit board. A switchable bass crossfeed filter mixes part of the left channel into the right and vice versa, which AudioValve links to lower listening fatigue on headphones. Volume is set with a large Alps logarithmic potentiometer, and a smaller knob beside it trims balance by up to 2 dB either way. A rocker switch on the front picks the source. After switch-on the unit needs about 30 seconds to become ready, and stereo level meters on the front light up. The metal case, in black or silver, also shields the circuit from outside interference. The USB version adds a player section for USB sticks, SD cards and FM with its own remote.
Pairing
With its wide load range, the Eartube handles most dynamic headphones, while the higher-gain input suits sources with a modest output level. AudioValve adds that the amplifier can also drive loudspeakers. Two gold-plated XLR sockets on the rear carry a volume-controlled signal, so the Eartube can work as a preamplifier for separate power amplifiers, with only pin 2 wired as the hot phase.
Alternatives
The AudioValve RKV Mark II is an output-transformerless headphone amplifier on four 6F5P valves, rated at 8 W per channel into 220 ohm.
Specifications
Model name
Eartube Mark II
Maximum Power, 32 Ohms (mW RMS per channel)
3500 (100 Ohms)
Maximum Power, 50 Ohms (mW RMS per channel)
N/A
Maximum Power, 300 Ohms (mW RMS per channel)
N/A
Maximum Power, 600 Ohms (mW RMS per channel)
N/A
Frequency response low +/- 3dB (Hz)
8
Frequency response high +/- 3dB (Hz)
80 000
Gain (dBu)
N/A
THD (% at 1V RMS, 300 ohms)
N/A
Signal to Noise Ratio (dB)
100
IMD (%, CCIR, 300 Ohms)
N/A
Crosstalk (dB, 20Hz-20KHz, 300 Ohms)
N/A
Output Impedance (Ohms)
N/A
Dimensions (mm)
380 х 110 х 260
Weight (kg)
8.0
Official link