Luxman L-550

1 9 8 1 august 1981
1 9 8 3

First of a very successful line of integrated amplifiers which would receive many awards and sell very well worldwide.

Designed and produced before the Alpine "takeover / collaboration" and just before the DAD revolution, the L-550 did receive a "State of the Art" award in 1982 besides being selected as "Best Product" by Stereo Sound.

Most of the direct followers also became Stereo Sound "Best Product" : L-550X, L-560 and the very successful L-540 and L-570.

All are versions of the same basic circuit : Single-Stage amplification, Duo-ßeta, plus-X, Circuit /S and Class A all the way, real hot Class A.
All did also sport something which was not to be discarded once the fad faded : double Heat-Pipes !

Power supply
Feeding all is a big 400VA EI transformer and two low-ESR 50V / 30,000µF 99,99% pure aluminium chemical caps.
Six windings feed separately the pre-driver, main Duo-ß, phono MM EQ amp, phono MM EQ Duo-ß, phono MC and protection / regulation / muting / pre-heating stages.
The power amp is fed separately from the secondary.

The necessary Heat-Pipes have vents top and bottom of the enclosure : 2x 50W of pure Class A produces heat, especially when idling current is to be set at 160mV for each channel !
The pre-Heating switch is used to get the L-550 reach its cruising speed while the power-on button is off ; current is cut from the final transistors but heats-up the rest of the circuit.

Single-Stage amplifier
As in all contemporary Luxmans, there is no second stage so the 1st stage uses a high Gm low-noise FET (for the MC input) with a 7mA current for the necessary gain.
If Duo-ßeta is used as usual in the power-supply, in the L-550, it also was implemented in the EQ phono section - that's Duo-ßeta Circuit /S.

Line level input reach the circuit where the "phono straight" mode starts, the latter bypassing the subsonic, high-cut, monitor and source selectors.
Unlike other contemporary LUX amps, the 9-turnover NF tone controls are not placed withing the power amp's main Duo-ßeta loop but the Linear Equalizer which can subtly tilt RIAA frequency response is.
The attenuator is a 2-gang 50kOhm pot sourced from, as always and for nearly everybody, ALPS, aka Alpine :)

Other features are... plenty :
Line-Phase sensor, front supplementray phono input, tape i/o and headphones output, three-way tape monitoring, 4-way tape dubbing, 6-position phono setting and warm-up indicator.
Plus pre/main i/o, all engraved front scripting and rosewood enclosure.

As for all of the L-550 series, the smaller models are, sonically, energetic bolids and the bigger models more relaxed providers : L-530 vs. L-550, L-530X vs. L-550X, L-525 vs. L-560 and L-540 vs. L-570.

Luxman L-550, image 1 Luxman L-550, image 2 Luxman L-550, image 3 Luxman L-550, image 4
Luxman L-550 specifications
Title Value
Power : 2x 50W (Class A, 20Hz...20Khz, 8 Ohm)
2x 70W (Class A, 20Hz...20Khz, 8 Ohm, german source)
2x 110W (Class A, 20Hz...20Khz, 4 Ohm, german source)
THD : < 0,005% (8 Ohm, -3dB, 20Hz...20Khz)
IMD : < 0,005% (8 Ohm, -3dB, 60Hz : 7Khz = 4:1)
Frequency response : 10Hz...100Khz (MAIN in ; -1dB)
20Hz...20Khz (Phono; ± 0,2dB)
Phono MM input : 1,6mV / 50kOhm - 100kOhm - 100 Ohm
Phono MC input : 80µV / 300 Ohm - 100 Ohm - 40 Ohm
Lines in : 220mV / 33kOhm
MAIN in : 220mV / 47kOhm
PRE output : 220mV / ??
S/N ratio : 84dB (MM ; IHF-A ; input shorted)
67dB (MC ; IHF-A ; 250µV input)
110dB (lines & MAIN in ; input shorted)
Bass control : ± 9dB
Bass turnovers : at 55 / 77 / 110 / 155 / 220 / 310 / 440 / 620 / 880Hz
Treble control : ± 9dB
Treble turnovers : 620 / 820 / 1,2k / 1,7k / 2,5k / 3,5k / 5k / 7k / 10Khz
Linear equalizer : ± 2 steps
Subsonic filter : 15Hz
High filter : 9Khz
PC : 310W max.
Dimensions : 45,3 x 17,4 x 46cm
Weight : 18kg.
Listprice : 250,000¥ (1981)
Features : > Subsonic filter
> High-cut filter
> Pre-Heating switch
> Mono switch
> Phono-straight switch
> Impedance selectors for phono inputs
> Signal-off switch
> Linear Equalizer (up tilt / down tilt)
> Switchable tone controls
> Switchable recording output
> Monitor + dubbing for three tape decks
> Switchable speaker outputs
> Headphones output
> Gold-plated RCA inputs
> Supplementary front inputs for phono and monitor
> Separable pre/main sections.
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page online since : november 2006
page updated : august 2010
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