Friday, 5 August 2016

Arcadia 7W PSE 2A3 Power Amplifier Upgrade

At the end of last year one of the original SJS Arcadia 7W PSE 2A3 amplifiers, originally built back in 1998, came in for a major service and upgrade.

Following the terminal exit of the main power transformer the opportunity was taken to upgrade and almost rebuild it.

The main power transformer was replaced by an external dual mono PSU, containing 6 mains transformers; two for the HT to the 2A3 power valves, two for the HT to the 6072A-5687 input/driver stage, and two for the negative bias supply for the grids of the 2A3s.



EZ81 rectifiers, choke input and first smoothing cap for the input/driver stage power supply are inside the PSU case


Four umbilical cables connect the psu to the audio chassis



Independent left and right mains switches, with remote switching controlled form the audio chassis


Removal of the power transformer from the audio chassis allowed for a pair of larger chokes to be fitted for the 2A3 HT supply, each channel has NOS GZ37 choke input supply and Elna Cerafine HT caps in the HT, and NOS Mullard EZ81 and choke input supply for the bias supply


Inside there was a major component refresh and upgrade; tantalum resistors, Hovland Musicaps, lots of Black Gates, Jensen 4 pole HT caps, Kemet bias supply caps and silver wiring



Not looking to shabby for it's age, and now fit and ready to go



Arcadia Model 5 Stereo SE 300B Power Amplifier

Following on from the successful launch of the SJS Arcadia Model 3 MM RIAA Phono amplifier, SJS Electroacoustics are pleased to present the matching all new bespoke Arcadia Model 5 stereo singled ended 300B power amplifier.


In common with other SJS Arcadia amplifiers it has been specifically engineered for sonic performance rather than technical specification, and fulfills SJS Electroacoustics primary design criteria:
  • Single Ended circuit topology
  • Pure Class A operation
  • Zero negative feedback
  • Valve rectification and choke smoothed HT power supply
  • 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
  • Real solid wooden frame
  • 4mm aluminium panels, black or natural anodized
  • Soundcare SuperSpiked feet

The Arcadia Model 5 power amplifier is a modern implementation of the classic 6SN7-6SN7-300B topology with a few tweaks, mainly in the psu design, component selection and layout.



The standard version is supplied with large wide bandwidth multi-section IE core output transformers, carbon film resistors and high quality film and copper foil coupling capacitors.

It is possible to upgrade this is stages to the Premier version including:

  • tantalum film resistors
  • Black Gate bypass capacitors
  • Dueland CAST DC coupling capacitors
  • Custom HiB double C-core output transformers
  • Pure silver wire for all point to point connections

Inside an Enhanced version:

Inside a Premier version


Technical Specifications

Input Impedance
100kOhm
Input Sensitivity
400mV for full output
Power Output
8W per channel
Frequency Response
+/-3dB 8Hz-30KHz
Valve Compliment
2 x 6SN7
2 x 300B
1 x 5U4G
Max. Power Consumption
250 Watts
Unit Weight
30 kg 
Shipping Weight
49 kg
(Original Packaging: Customised flight case)
Unit Dimensions
300mm (h) x 450mm (w) x 400mm (d)
Shipping Dimensions
400mm (h) x 545mm (w) x 500mm (d)

(Original Packaging: Customised flight case)



Design Options

The Model 5 SE 300B power 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.

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 coupling capacitors, power supply capacitors or resistors, for example, these can be discussed at the point of ordering.

Thursday, 10 March 2016

North West Audio Show


We are pleased to announce we will be exhibiting 

at The North West Audio Show on Sunday 26th June 2016


THE SHOW

Now in its third year, the Northwest Audio Show is set to become one of the highlights in the audiophile calendar. With great exhibitors, top brands and a superb venue, we believe that the North West Audio Show gives attendees the opportunity to hear the very best audio in surroundings that are second to none. Register and secure your free tickets today.

IT’S FREE

Free entry, free parking, a day surrounded by the best in audio and all in the beautiful settings of Cranage Hall and Wychwood Hall, Cheshire. The event organisers will also be laying on a free shuttle bus between the venues.

Friday, 30 October 2015

Arcadia Line Level Preamplifiers


Between 1996 and 1998 the original run of SJS Arcadia Model 1 and Model 2 line stage pre-amplifiers were delivered. Over the past few years a number have been back for service, repairs or upgrades, so I thought it may be useful to present some of the original information here.


SJS Arcadia Model 1 and Model 2 Line Level Preamplifiers

6 line inputs, 2 tape loops, 10dB of gain, zero feedback
finest quality components, musical results

The Arcadia bespoke line level pre-amplifiers offer the very finest musical results for all high quality systems. When paired with one of the matching Arcadia phono stages vinyl reproduction will obtain a level far beyond that of an integrated pre-amplifier.

By carefully balancing all aspects of the design, the Arcadia line level pre-amplifiers offer a level of gain and drive suitable most power amplifiers; whether valve or solid state. Utilising a special valve rectified, choke filtered, power supply, and avoiding sonically degrading feedback; the Arcadia pre-amplifiers offer a natural tonal balance, which is fluid, of full tone and grain free. The strong dynamics are balanced by a deft touch to produce an enlightening musical experience.

The Model 2 builds upon the strengths of the Model 1 and improves all aspects of performance whilst retaining the dynamic capabilities and control of the Model 1. Built with a completely copper chassis, and the very highest quality components available, the Model 2 offers a level of coherent transparency unmatched at the price.

CONSTRUCTION DETAILS & FEATURES

All valve line level preamplifier

  • Separate Listen and Record selectors
  • Hard wired throughout
  • High regulation choke power supply
  • Zero feedback gain stage
  • Very high parts quality including:
    • Hovland Musicaps 
    • Mills resistors 
    • Alps "Black Beauty" volume control 
    • Noble balance control.


  • Model 2 also features:
    • All copper casework 
    • OS-CON caps 
    • Panasonic volume pot 
    • PTFE insulated pure silver wiring



 

TECHNICAL SPECIFICATIONS

Line Level Inputs: 6
Preamp Outputs: 2
Tape Outputs: 2
Input Impedance: 100K ohms
Gain: 8dB
Valves: 2 x 5687 in early units replaced by 2 x 6111WA in later units, 1 x 5Y3
Frequency Response: <5hz to >150KHz at -3dB
Dimensions h/w/d: 150mm x 225mm x 390mm
Shipping Weight: 9 Kgs 

UK Retail Price (1996-1998): Model 1: £995, Model 2: £1995

"There's none of the wispy airiness and soft, slow bass that one associates with the breed - just consistently fine tone, edge-of-your-seat dynamics and effortlessness." Jason Kennedy on the Model 1 in HiFi Choice Sept '97.

Download HiFi Choice Review

Please Note: 

All Units are now SOLD and no longer in production.
We are pleased to offer servicing and upgrades for all original production units.
Please contact us for further details.

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


Monday, 20 April 2015

Welcome

Hello and welcome


This is the beginning of the new SJS Electroacoustics blog. The plan is to try to bring together information on the SJS Arcadia valve amplifiers, some interesting repair or refurbishment projects, and details of the new custom amplifiers in development.

The archive section will develop with data on the amplifiers built during the late 1990s, and gradually replace the old long suffering web site which has sat undeveloped too long.



Let's see how it develops, and if you want to get in touch just drop me a message.

Best of luck
Simon