Sparkos Gemini Headphone amplifier

Main view of SPARKOS GEMINI headphone amplifier
This Gemini headphone amplifier/preamplifier from Sparkos is a jewel of hybrid technology, whose main feature is the possibility of customizing it to suit your listening preferences and your Hi-Fi installation. It's called hybrid because its amplification stage comprises both a 6922 tube (also known as an ECC88) and a SS2590 discrete AOP.

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Shipping date: 23-04-2024.

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SPARKOS GEMINI Hybrid Headphone amplifier / Preamplifier Tube 6922 and AOP SS2590

Front view of SPARKOS GEMINI

This Sparkos Gemini headphone amplifier/preamplifier is a jewel of hybrid technology, whose main feature is the ability to customize it to suit your listening preferences and Hi-Fi setup. It's called a hybrid because its amplification stage consists of both a 6922 tube (also known as an ECC88) and a SS2590 discrete AOP, as well as other high-fidelity components such as an ALPS Bluet Velvet volume control potentiometer and Sparkos Labs voltage regulators. Its design enables it to achieve top-level performance with :

  • Low output impedance < 0.25 Ohms
  • A very wide gain frequency response 10Hz - 100KhZ
  • Considerable output power with up to 2W @ 32Ω and 750mW @ 300Ω
  • THD of 0.1% to 1.5%, depending on settings

Overall, the Sparkos Gemini has a warm, harmonically rich sound signature that will bring depth and relief to your favorite tunes. Its connectivity makes it a formidable ally that will integrate easily into any Hi-Fi installation: XLR 4-pin headphone output, 4.4mm jack headphone output, as well as an RCA line input and an RCA line output enabling it to be used as a preamplifier.

Sparkos Gemini: the path of the audio signal in an innovative architecture

The first component encountered by the audio signal is the Sparkos Gemini's amplifier tube, following its encounter with the Alps Blue Velvet volume controller. The audio signal is then extracted by a current mirror and transmitted to the SS2590 discrete AOPs of the headphone and RCA line outputs. The structure of the Sparkos Gemini is therefore devoid of coupling capacitors, which is rare in tube amplifier design. Sparkos has taken a different approach, using a current mirror and a DC servo that suppresses the bias current and allows only the audio signal to pass through.

Presentation of the internal architecture of SPARKOS GEMINI

Sparkos Gemini: different levels of customization

The first level of customization lies in the fact that the Sparkos gemini tube can be replaced by a multitude of compatible tubes: 12AX7, 12AT7, 12AU7, 12AY7, 6AQ8, 5751, 6CG7, 6N1, 12BH7. This is made possible by an internal jumper.

Tube TypeOther designationsJumpers configurationNotes
6922ECC88, 6DJ8Type 1Tube supplied with the Saprkos Gemini.
12AX7ECC83, ECC803S, 7025Type 2Popular guitar amplification tube with lots of harmonics.
12AT7ECC81, 12AT7WCType 2Similar to 12AX7 but with stronger polarization and higher current.
12AU7ECC82, 6189, ECC802SType 2Similar to the previous two, but the biases are even stronger. Gain is lower.
12AY76072Type 2 Similar to above, but polarizes with less current.
6AQ8ECC85Type 1Originally an RF amplifier tube, odd-order harmonics dominant at high volume.
5751-Type 2Similar to 12AX7 but with less gain.
6CG7-Type 1Old vertical deflection amplifier for cathode ray tubes, slightly longer.
6N1-Type 1Generates a lot of warmth and lower harmonic levels
12BH7-Type 2Popular in Mcintosh amplifiers, slightly longer length, mainly even-order harmonics

The second level of sound customization is made possible by gain switches on the front panel. Each tube used will have a particular sound signature. This gain allows you to intensify the final sound signal. In fact, this gain offers simple and immediate control over the level of force with which the tube should work. This gain setting also has the effect of modifying the perceived volume level by 10dB.

The third level of customization lets you control the amount of current at which the tube is polarized. This is also made possible by an internal jumper.

Jumper caps make it quick and easy to select the configuration of the various internal jumpers.

Sparkos Gemini: jumper-selectable input attenuator

A third internal jumper attenuates the input level by -15dB. This can be used if you're feeding the Sparkos Gemini with a source device that's too powerful, or if you're using it with high-sensitivity headphones that make the volume level too high. This jumper effectively attenuates the input signal, giving you a higher range of volume control.

Sparkos Gemini jumper configuration

Here you'll find the different jumper configurations for Sparkos Gemini. For further details, please refer to the user manual you can download from our download section.

Internal jumpers on the SPARKOS GEMINI
Zoom jumper 1

#1 Tube changing jumpers

You can use any type of double triode tube in the Gemini. However, the tube type jumper must be set appropriately, to either Type 1 or Type 2. Simply refer to the SPARKOS Gemini tube compatibility chart.

Zoom Jumper 2

#2 Tube bias adjustment jumpers 

This jumper lets you adjust the intensity of the tube's sound signature. Without activation of the jumper, the intensity setting will be high, whereas if you add the cap, the intensity setting will be lower. The jumper is set to high polarization on receipt of the product.

Zoom jumper 3

#3 Input attenuation jumper

The functionality of this jumper lies in lowering the input volume by 15dB for use with high-sensitivity headphones and in-ear monitors where the volume would otherwise become too loud. The Sparkos Gemini is delivered with the jumper activated and therefore without the attenuation.

Caution for the first Jumper (#1) concerning tube change, it is imperative never to use Type 1 and Type 2 jumpers at the same time. In other words, never install two jumper caps on the two slots at the same time.

Technical characteristics

Product typeHeadphone amplifier
Amplification typeHybrid: Tube + OPA
Supplied tube6922
InputRCA line input
Output1x XLR 4-pin headphone output
1x 4.4mm jack headphone output

1x RCA stereo line output
Input attenuation-15dB
DC protection for headphone outputs
Output impedance< 0.25 Ohm
Frequency response10Hz - 100kHz
GainLow gain : 12dB
High gain : 21.5dB
Crosstalk> 100dB @ 1kHz
Output power2000mW @23 Ohms
720mW Max @ 300 Ohms
Max. output voltage/current15V 250mA
THD0.1% - 1.5% (depending of setting)
Noise10uVrms low gain
30uVrms high gain
SNR120dB max; low gain
110dB max. high gain
Power supply240V AC (power cable not supplied)
Dimensions229 x 152.5 x 51mm
Net weight1.92kg
Package1x Sparkos Gemini headphone amplifier / preamplifier
Data sheet
OutputJack 4.4mm
Remote ControlNo

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SPARKOS GEMINI Hybrid Headphone amplifier / Preamplifier Tube 6922 and AOP SS2590
This Gemini headphone amplifier/preamplifier from Sparkos is a jewel of hybrid technology, whose main feature is the possibility of customizing it...

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