Features
Available to previous customers direct for £220/€260/$300, the SPARTAN 6 re-imagines the original SPARTAN 5 design, based around a single active stage using improved surface-mount components. The SPARTAN 6 features a higher-accuracy RIAA equalisation network, uprated power supply components, and a new amplifier IC. Tighter playback is delivered with a higher output level, while the always-on power consumption stays as low as before.
Limited red version, frontal view
New ceramic capacitors replace the polypropylene-film types used in the infrasonic input filters and radio-frequency interference rejection networks. Thanks to the lower parasitic qualities of these surface-mount components, total input capacitance has been reduced from 120pF to 90pF, with no loss of immunity to ambient interference. Stricter tolerances in the second-order 20Hz subsonic filter also keep the cut-off point considerably closer to its ideal. The filter now yields a flat response all the way down to 40Hz, while attenuating vinyl surface disturbances in the 10Hz cartridge-arm resonance region by over a factor of four.
Rear connections on green version
The novel unregulated power supply features uprated components throughout, with 47% more reservoir and filtering capacitance, and full DC and over-voltage protection from both power surges and the connection of incorrect third-party adapters. Unlike conventional regulated power supply sections, this one delivers 100% of its input current to the low-power OPA1642 amplifier stage, with zero quiescent draw or regulator overhead. This results in exceptional power efficiency, consuming less than 3.5kWh per year when plugged in continuously, negating any need for a power switch and start-up circuitry.
Green version, one of four to be made
Keeping the linear transformer outside of the small enclosure prevents its magnetic fields from affecting the audio circuitry. The split-rail design prevents non-linear amplifier power currents from flowing into the zero-Volt reference path where they can induce distortion. This arrangement also allows the circuitry to reach its optimal operating point within seconds of powering up: no burn-in or waiting around for stabilisation needed!
Specification
As the SPARTAN 5’s NJM2068 amplifier IC was reaching the end of production, a new device had to be selected for the beating heart of the circuit. After exhausting all of the readily-available parts on the market, the Burr-Brown OPA1642 was finally chosen for its excellent low-input noise and output characteristics. The JFET input’s complete lack of input-current noise results in much lower low-frequency noise generated across the high-impedance subsonic filtering network, while the rail-to-rail output stage increases the maximum output from 8.5 to 9.5V RMS: a very welcome extra 1.7dB of overload margin.
| Parameter | Measurement |
|---|---|
| Gain at 1kHz, 10kΩ line load | 40dB, 100x |
| RIAA accuracy | ±0.15dB, 40Hz to 22kHz |
| Channel balance | ±0.15dB, at 1kHz |
| Channel separation | 80dB, 20Hz to 22kHz |
| SNR, ref 5mV, cartridge load | 76dB, 6300x, 220Hz to 22kHz |
| Overload margin, ref 5mV | 25.6dB, 19x |
| Maximum input at 1kHz | 95mV RMS |
| Maximum input at 10kHz | 450mV RMS |
| Maximum output, 5kΩ line load | 9.5V RMS, 20Hz to 25kHz |
| THD, +20dB ref 5mV input | <0.002%, 20Hz to 22kHz |
| THD, at 9.5V RMS output | <0.004%, 20Hz to 22KHz |
| Input capacitance | 90pF |
| Input resistance | 48kΩ, ±1% |
| Output impedance | 90Ω |
| Minimum line load impedance | 5kΩ |
| Subsonic filter | 20Hz, 2nd order, -13.5dB at 10Hz |
| Power supply | Split linear ±14.5V |
| Power consumption | <0.5W |
| Dimensions (W*H*D) | 110*46*110mm |
The RIAA network is upgraded, with 1%-tolerance C0G capacitors diminishing the worst-case response error (±0.15 dB vs ±0.25 dB previously), for even lower colouration than before. Imaging also benefits from a similar improvement in channel balance.
Output impedance is also reduced to 90Ω from 100Ω. Extra immunity to even the most diabolical levels of radio hash is also added, with series-shunt filter networks preventing any unwanted energy from getting in even through the outputs.
