Overview
At £500, the SPARTAN 12 carries the triple-stage topology of the PRO series into a smaller form factor with a simplified feature set. With noise-suppressing active loading on the front end, a 50dB gain setting for high-output moving coil cartridges and the same equaliser used in the LO PRO, it represents a version of the MM PRO design more suited to simpler setups using RCA connections.
Standard black SPARTAN 12, frontal view
This state-of-the-art design fully embraces surface-mount technology, using next-generation NJM8068 input amplifiers in the flat-gain input amplifier that makes up the first stage. Their balance of voltage and current noise is perfectly optimised for the impedance characteristics of typical MM cartridges. Active loading tackles the noise contribution of the cartridge-loading resistance to match the market-beating 79dB SNR figure delivered by the MM PRO with a real cartridge connected. For HOMC, voltage noise alone remains low enough to yield a very respectable 76dB against a 2mV 200Ω cartridge.
Surface-mount PCB, using new ICs
The RIAA equaliser amplifier in the intermediate second stage uses the same components as the new LO PRO moving coil design, leveraging high-stability C0G capacitors and helical thin-film resistors. As they are doubled up in parallel combinations, their tight 1% tolerances are further averaged out to hold the SPARTAN 12s RIAA compliance comfortably within the conservatively rated ±0.1dB official figure, resulting in zero audible colouration.
Tripled arrays of ceramic capacitors in the subsonic filter maintain the strict RIAA accuracy all the way down to 35Hz, passing the cut-off point of 20.5Hz to attenuate the inevitable surface disturbances of vinyl by a factor of 10 in the 10Hz danger zone of arm-cartridge resonances. As the final 6dB of gain is applied after the subsonic filter, the excellent overload margin of 24.5dB runs all the way down from 27kHz to well under 20Hz. In addition to the 42/50dB gain switch for HOMC level matching, dual-setting low-frequency cross-feed and mono-summing switches are neatly bridged into the filter network.
Rear view, showing RCA connections
The third and final stage employs an uprated version of the tried-and-true 5532 amplifiers used in the PRO series. To ensure all amplifiers in the signal path remain as linear as possible, the total gain burden is balanced between the three stages, resulting in less than 0.001% of overall harmonic distortion at the maximum output voltage of 10.5V RMS. The superb load-driving ability of the 5532 maintains this distortion figure with line loads an order of magnitude lower than the typical 10kΩ. Radio frequency filter networks are embedded in the line output networks to remove all points of unwanted ambient ingress in even the harshest environments.
Frontal view on black background
Power is supplied to the unit by a external linear transformer, keeping magnetic fields outside of the enclosure where they might disturb the sensitive input amplifiers. The remaining power supply circuit inside the unit rectifies and regulates the transformer's 9V AC output into precise dual ±17V rails using external voltage reference diodes. As the amplifier stages are energised through separate positive and negative rails, as opposed to a single rail and ground, their non-linear power currents are entirely excluded from the circuit's reference point with no possibility of inducing distortion when excited by a signal.
Unlike single-rail designs that require rail-derived biasing networks to transpose the peaks and troughs of an AC audio signal halfway across the power supply, the SPARTAN 12's dual rail arrangement needs no voltage bias for the output to follow both negative and positive directions of the signal. As a result of the natural zero-Volt biasing of every amplifier stage, any residual power rail noise and fluctuations have no route whatsoever into the signal path. The lack of power-rail bias also allows the circuitry to stabilise almost instantly, settling fully by the time the 2-second output muting relay closes: no need for silly "burn-in" scams or waiting around to get going!
Over-voltage protection on the 9V AC input, for cases of accidental connection of inappropriate adapters or poorly-matched fraudulent third-party products, is also implemented to help improve the chances of survival when operated outside of warranty conditions.
Specification
| Parameter | Measurement |
|---|---|
| Gain at 1kHz, 10kΩ line load | 42dB (125x), or 50dB (316x) |
| RIAA accuracy | ±0.1dB, 35Hz to 25kHz |
| Channel balance | ±0.1dB, at 1kHz |
| Crosstalk | <72dB 20Hz to 22kHz |
| SNR, 5mV MM, 500mH + 600Ω | 79dB, 220Hz to 22kHz |
| Overload margin, MM | 24.5dB (16.8x), ref 5mV at 1kHz |
| SNR, 2mV HOMC, 200Ω | 76dB, 220Hz to 22kHz |
| Overload margin, HOMC | 24.3dB (16.5x), ref 2mV at 1kHz |
| Maximum input at 1kHz | 94mV RMS MM, 8.5mV RMS MC |
| Maximum input at 10kHz | 450mV RMS MM, 41mV RMS MC |
| Maximum output, 3kΩ line load | 10.5V RMS, 20Hz to 27kHz |
| THD, 10.5V RMS output | <0.001%, 20Hz to 22kHz |
| Input impedance | 50kΩ + 90pF |
| Output impedance | 90Ω |
| Minimum line impedance | 1kΩ |
| Subsonic filter | 20.5Hz, 3rd order, -20dB at 10Hz |
| Low-frequency cross-feed | 100Hz or 200Hz, -9 or -13.8dB at 40Hz |
| Power consumption | 3W at full output, 0.2W powered off |
| Dimensions (W*H*D) | 172*60*130mm |
