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Solo SRG II Headphone Amplifier

The latest edition of our flagship Solo headphone amplifier - the SRGII (Studio Reference Green MK II) puts a real life force behind the music.

Looking back, What Hi-Fi? Sound and Vision said this about the Solo 2004 edition headphone amplifier...

Five years of serious development later - would five stars now be enough to appraise the Solo SRG II headphone amplifier?

The Solo SRG II headphone amplifier combines conventional negative feedback with line driver load sensing to exert greater control over your headphones where it is needed.

It therefore reduces or eliminates altogether the comb-filter effect most headphone impedance curves exhibit in the upper midrange and treble frequencies. It also ensures correct matching with the widest range of headphones and overcomes cable capacitance and inductance problems which could otherwise strip the music of its airy qualities and sound staging. The Solo SRG II headphone amplifier does everything better as well as giving a more weighty bass.

The Solo SRG II headphone amplifier has two line level inputs and a front panel input selector with centre off. It is housed in a strong anodized aluminium eurocard style enclosure. The volume control also acts as sensitivity adjuster and therefore the full rotation can be used (see further explanation below). The Solo SRG II headphone amplifier is suitable for use with headphone impedances from 16 Ohms to 600 Ohms.

The "Green" Headphone Amplifier

We also made it energy saving! You can buy the Solo SRG II headphone amplifier with an energy efficient power supply complying with world carbon reduction targets for nearly 30% less than the PSU1 powered standard issue.

The Solo SRG II headphone amplifier is available with PSU1 power supply for those wanting a traditional (but more power hungry) linear power supply.

Headphone Matching, Suitability and Volume Control Settings

The Solo SRG II is designed to work, and self adjust, on two different input levels (in either switch position): 1] professional (unbalanced) 0dB: 775mV, where its output is to drive 600 Ohm headphones for certain studio applications, and 2] domestic -10dB (DIN): 250mV, where its output is to drive 32 Ohm headphones. In either mode of use it will return virtually identical output power as well as similar sound pressure levels with identical headphone sensitivities.

In typical usage however, it will be used with different headphone impedances in the  range 16 - 600 Ohms, having quite different headphone sensitivities (SPL), and input levels between 250mV and 1V. This gives a number of permutations which could not be covered with a gain setting switch, and instead, the Solo SRG II uses a combination of IEC/DIN 61945 headphone amplifier output "matching system" with an accurate Alps volume control which is used over its entire range to accommodate such widely differing conditions of use.

As such the user may find the ideal volume control position required for his/her listening tastes considerably different to that of a hi-fi amplifier. The left-right track matching of the volume control is adjusted by Alps, its manufacturer, for best channel balance between its 9 o'clock and 3 o'clock settings and as such when set for zero volume some residual signal may be heard on one channel and not the other - this is normal and part of the volume control design.

Specification

Headphone impedance range: 16 to 600 Ohms preferred; 8 to 2,000 Ohms acceptable

Headphone Jack: 1/4 inch (6.35mm) A gauge (BPO B gauge to special order)

Power output
(rms, both channels fully driven) 32 Ohms: 27mW/channel; 600 Ohms: 23mW/channel

Distortion (THD plus noise, ref 1kHz): 0.02%

Frequency response (-3dB) 32 Ohms load: 27Hz - 35kHz; 600 Ohms load: 10Hz - 39kHz

Output noise (20Hz-20kHz, CCIR quasi-peak): -84dB

Input sensitivity (for specified power output) 32 Ohms: 250mV rms; 600 Ohms: 775mV rms

Channel balance: better than 1dB, "9 to 3 o'clock" positions

Crosstalk: Left to Right -57dB; Input to Input -68dB

Mute: Signal off mute, non-shorting

Output Stage: Bipolar class AB

Supply voltage: 24V DC

Size: (approx.) W: 107 x H: 50 x D: 185 (mm) inc. controls

Price

£434.00 supplied with PSU1 power supply; £314.25 supplied with energy saving power supply. Prices in GBP (pounds sterling) ex VAT/GST