LA4 MkIII line pre-amplifier

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Building on the success of the earlier marques the LA4 MKIII has improved cosmetics and an upgraded circuit. Now with lower feedback and lower gain the macro dynamics and sound stage are enhanced.

A deceptively simple high quality single stage design followed by an output buffer. But what makes the LA4 III special is the power supply and our “finely tuned” design. A high end pre amplifier must have the best power supply. The LA4 MK III has two chokes in double Pi configuration for well conditioned power giving superb smoothing for velvety inky black silence. The rectifier valve, which makes a surprising difference, is the excellent 274B. This outstanding Western Electric design is probably the best sounding power valve available.

The three audio valves we use are the 6SN7 double triodes. This 1940 vintage valve has all the best characteristics for the job, and its larger size means long life and good stability. Also the sound is more musical as we feel these have a more fluid sound. You can experiment with both vintage and modern types.

Built to last

Like all our equipment the LA4 III is very solidly made. It has a heavy alloy and steel chassis. The internal wiring is all “point to point”, “hand wired”, this is essential for valve amplifiers, and allows for upgrading to larger capacitors, and makes future servicing very simple.

Specifications and Features

• Comprehensive manual supplied
• Full instructions for valve change included
• All hand wired point to point
• No printed circuit board to ‘colour’ sound
• ALPs Blue motorised volume pot.
• All Triode design
• 3x 6SN7 valves
• 274B Valve rectifier (also use GZ34/5AR4/5R4)
• Double Choke HT supply
• DC heater supply
• Signal to noise level -90db
• Freq response 20hz-20khz +0 – 0.1db
• Total harmonic distortion typically less than 0.1%
• Gain x4, 12db#
• Max input level 5v for 20v output#
• Very low output impedance of 100Ω#
• Suitable for power amps 100mv-5v sensitivity
• Attractive valve cover available (£50 extra).
• High quality 2w metal film, & wire-wound resistors
• Solen/SCR audio capacitors (Jensen upgrade option)
• Silver PTFE audio cable
• Gold plated Input terminals
• Four line inputs
• Tape monitor circuit and record output
• 220/240volts 100watts
• C E compliant
• 250W, 370D, 230H (with 274B and cover), or 175H with GZ34 (no cover) 12kg packed#
(Specifications subject to change, errors & omissions excepted 04/10/12)

Various valve and capacitor upgrades are available

MK II Line Pre-amplifier Leaflet