Friday, 19 June 2015

Arcadia Model 3 Valve MM Phono Amplifier

Approximately 15 years since the Arcadia Model 1 and Model 2 line stage preamplifiers ceased production, SJS Electroacoustics are pleased to present the all new bespoke Arcadia Model 3 all valve moving magnet RIAA phono amplifier. 


Cherry with natural anodized aluminium


It represents a modern extension of the design philosophy behind the original SJS Arcadia amplifiers and has been specifically engineered for sonic performance rather than technical specification, and fulfils all SJS Electroacoustics primary design criteria:
  • Single Ended circuit topology
  • Pure Class A operation
  • Zero negative feedback
  • Valve rectification and choke-input HT power supply
  • HT power supply without electrolytic capacitors
  • Custom made HT T-network power supply capacitors with silver leads
  • Separate mains transformers for HT and filament supplies
  • Point-to-point circuit wiring without PCBs
  • Hand built
  • PTFE board for component mounting
  • NOS Hovland MusiCap coupling capacitors
  • Low resistance RIAA network using MusiCap film/foil capacitors
  • Real solid wooden frame
  • 4mm aluminium panels, black or natural anodized
  • Soundcare SuperSpiked feet
The Arcadia Model 3 Moving Magnet phono stage uses a triode-wired D3a common cathode valve for the input stage, to provide high gain, excellent linearity, high overload margin and exceptional transient response. This drives the low impedance resistor-capacitor (RC) passive RIAA filter, with a high gain EC8010 valve as the output stage.

The detrimental effects of electrolytic capacitors in the audio circuit are avoided by utilising custom designed and made film capacitors in the power supply, with each gain stage having its own choke-capacitor filtered branch of the supply. This approach extends to the audio circuit where the use of electrolytic capacitors for cathode bypass has been avoided by running the first stage biased with a SiC diode, and the second stage using fixed battery bias on the grid. These design solutions deliver a dynamic fast and clean presentation, whist preserving the tone, clarity and effortless grace of a good valve amplifier.

The avoidance of a cathode follower output stage provides a significant benefit to the musical delivery of the unit, however it does mean that it is not a universally applicable phono amplifier and for optimum performance has been designed to be used in a system where the following preamplifier stage has an input impedance of 100 kOhm. It may be used in systems where the following preamplifier stage has an input impedance as low as 20 kOhm however there is likely to be a reduction in bass performance in this case. If there is a desire to use the unit with a load below 100 kOhm on a long term basis, it may advisable to discuss having the unit customised to suite with SJS Electroacoustics directly.


Maple with black anodized aluminium

Technical Specifications

Input Impedance
47 kOhm
Input Sensitivity
5mV for 1V Output
Gain
46 dBV
Output Impedance
 <2 kOhm
Valve Compliment
2 x D3a
2 x EC8010
2 x 6BY5
Max. Power Consumption
70 Watts
Unit Weight
19 kg 
Shipping Weight
30 kg
(Original Packaging: Customised flight case)
Unit Dimensions
148mm (h) x 450mm (w) x 400mm (d)
Shipping Dimensions
240mm (h) x 545mm (w) x 500mm (d)

(Original Packaging: Customised flight case)

Design Options

The Model 3 valve MM phono amplifier is hand built to order in England, and therefore we are able to offer customisation to meet your aesthetic and sonic preferences. the solid wooden chassis is available in a range of four standard choices; cherry, maple, light oak and walnut with others such as zebra wood available to special order. The chassis panels are available in either natural or black anodised aluminium as standard, with other colours, such as blue, red or gold, available to special order.



Light Oak with natural anodized aluminium


Bespoke customisation of the internal components is also possible to meet our clients' specific requirements, whether it be for use of a certain interconnect cable between the phono sockets and the circuit, or replacement of the NOS Hovland MusiCaps with Dueland RS or CAST or possibly even using Tantalum film resistors, for example, these can be discussed at the point of ordering.



Walnut with black anodized aluminium


Internal layout