SPARTAN 30 BY MICHAEL FIDLER HIGH IMPEDANCE HEADPHONE AND LINE AMPLIFIER

Hand made in Kent, England using all through-hole technology, the SPARTAN 30 by Michael Fidler headphone and line preamplifier takes “a new look at traditional potentiometer-based preamplifiers”.

Michael tells us it further increases practical performance through original circuit architecture, resulting in a compact device that can replace traditional integrated amplifiers when used with active speakers.

SPARTAN 30 BY MICHAEL FIDLER HEADPHONE AND PRE AMPLIFIER

Three high-impedance RCA line inputs ensure minimal insertion loss with modern and vintage equipment alike, with electromechanical selection being performed via Panasonic relays right at the input connectors. A new active volume control circuit with an inherently balanced output eliminates the need for extra circuitry on the line outputs for a shorter signal path with lower noise. Decreasing the value of the potentiometer from the more conventional 10kΩ to 5kΩ also reduced the noise power by a factor of two.

POTENTIOMETER

As the volume control is the most essential control in any sound system, a great deal of time was spent sourcing the potentiometer. During development, all the conventional devices tested in the design failed to meet the project’s channel tracking and lifespan requirements. After many hours of searching, a custom part, rated for 5 million cycles and initially intended for industrial applications, was then commissioned to ensure good stereo consistency for years to come.

OP-AMPS

Professional quality NJM5532 op-amps, mounted in turned IC sockets, are used for the line input and volume control stages, leading to a dynamic range of over 128dB with less than 5ppm distortion at 0dB gain. Thanks to the ±17V internal supply rails, they can deliver over 21V RMS of undistorted output at the XLR connectors and tolerate 10.5V RMS maximum input, making overload with even the hottest source signals very unlikely.

HEADPHONES

The headphone output, designed for work with the most critical high-impedance types, uses purpose-designed NJM4556 high-current op-amps, found in some of the best Japanese equipment from the 1990s onwards. Separate chips for each channel working in parallel pairs allow for over 700mW per channel to be delivered into a 150Ω load, halving the noise power of each amplifier section. Their operation as unity gain buffers keeps distortion below 0.001% at 500mW output.

SPARTAN 30 BY MICHAEL FIDLER POWER SUPPLY

The power supply uses high-reliability Panasonic electrolytic capacitors with precise diode references and an external transformer to keep hum-inducing magnetic fields well outside of the main enclosure. Improved transformer magnetics limit standby power consumption to under 0.2W. The linear operation affords much better mains isolation than switching supplies and precludes switching noise from getting into audio path.

A startup mute circuit operates three Panasonic telecoms relays on the line and headphone outputs at start-up and switch-off to restrain any unpleasant transients. When a jack is inserted into the headphone connector, the two line output relays automatically mute the line output. A sandblasted anodised aluminium enclosure completes the fit and finish.

SPARTAN 30 BY MICHAEL FIDLER HEADPHONE AND PRE AMPLIFIER PRICING AND AVAILABILITY

The SPARTAN 30 is now available to order worldwide direct from Classic Audio Ltd. for £450 in the UK, €550 for EU countries, and $600 for the USA. Payments are also accepted in Australian and Canadian dollars. Prices are inclusive of shipping costs but not necessarily import duties which may vary from country to country.

GB 240V, EU 220V, and US/NEMA external transformers are supplied as standard to respective regions.

HiFi PiG Says: A well priced and well made looking new headphone and pre amplifier.