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Inside a Luxman L-530 amplifier
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March 07, 2012, 06:23:59 AM
  • lshin80
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A relative of ours asked my dad to service his Luxman L-530 amplifier. He bought this amp new in the early 80's and used it for a long time to listen to vinyl. He then stopped using it for a long time, when he recently turned it on to see if it was still working. To his (bad) surprise, the amp didn't work and in few seconds it emitted a bad smell, as if something inside was burning...
My dad checked it out and determined that the leads of the left loudspeaker cable had tore up, thus not making contact and creating a short circuit that fried the left channel power transistors and a couple of resistors, before the protection circuit could act and prevent the damage.
These transistors are long time out of production, so my dad had a hard time in finding two couples, but he eventually managed to catch them in Honk Kong through eBay. After a painful bias calibration (the transistors were not matched to their right channel counterparts) and the replacement of the damaged resistors, the amp finally came back to life.

This amp's peculiarity is that it works in class A when operated at low to mid power, but when you turn up the volume it switches to class AB.
The amp has an anti-bump circuit to prevent speakers damage; it also has multiple protection circuits that turn it off in case of overheating or voltage peaks, and a led on the front panel tells you when the amp has warmed up for better tone (typically 10 minutes).
There are two phono inputs, a MM and a MC; two more line input, and various output for tape recording. There is a phones output on the front panel, while you can connect two couples of speakers on the rear; each of them can be muted anytime through a couple of switches on the front.
There is one volume knob, and one balance control. The tone regulation circuit can be bypassed, and consists of one bass and one treble knob, each of them working with a selector knob for several frequency turnover settings.
Construction is solid, with neat wiring. However assembly / disassembly is not very easy or comfortable, due to the components "crowding".

Soundwise, it's rock-solid, precise, very solid state style but in a good way, not harsh. Very dynamic and imposing sound. Compared to my Nuova Elettronica IGBT power amp (but that's an unfair comparison, there are 18 years of technological advances between the two amps...), they are very similar, with the Luxman lacking a bit of bass, but the difference is hardly noticeable.
Oddly, the MM phono input, paired to my Denon dl-110 high output MC cartridge, behaves conversely, showing a slight decrease of the mids and of the trebles; it has three impedance settings of 50K, 100k and 100 ohms but I can't speculate on the difference on tone, because my Denon is almost unaffected by impedance variations. Only the 100 ohms setting caused a dramatic loss of volume.
The frequency turnover settings really don't affect heavily the sound, and when you turn the bass and treble knobs, the change in tone is quite bland.

Pictures below.

« Last Edit: September 17, 2014, 01:14:45 AM by BSD2000 »
Pro-Ject RPM 5.1 Denon DL-110 Sony BDP-S373 Fred Nachbaur High Precision Tube Phono Preamp Nuova Elettronica FET preamp Nuova Elettronica IGBT power amp Mission 701 Clicktronic cables Norstone Loudspeaker Cable


March 07, 2012, 06:30:19 AM
  • lshin80
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More pictures with components details.


March 08, 2012, 01:39:55 AM
    • VinylAudio.net
  • BSD2000
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Wow, that looks awesome. Very well built. Glad to hear you were able to bring it back to life!  8)

My Parasound amp runs the same way; the first 20 watts or so are class A, then it switches to class AB.

I usually load my cartridges at 47K ohm (ie; 'wide open') and I notice my Zyx cartridges begin to sound dull and 'choked' below 1K ohm loading. But then again, loading has a bigger effect on moving magnet cartridges and much less, but still noticeable, effect on moving coils. It's strange that the Luxman doesn't have higher loading on the moving coil settings than 300 ohms, but the moving magnet settings go up to 50K. Is the switch only for loading, or does it also change the gain factor?
Rega P25 Zyx Omega G Zyx R100H Audio Research PH5 Denon DP-52F Denon DL-103D Burson HA-160 Sennheiser HD-650 and HD-800


March 08, 2012, 11:40:53 AM
  • lshin80
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It's strange that the Luxman doesn't have higher loading on the moving coil settings than 300 ohms, but the moving magnet settings go up to 50K. Is the switch only for loading, or does it also change the gain factor?
There's no indication about that on the manual, but it should be fixed gain. The MM input sensitivity is 2.0 mV; MC is 0.125 mV. Maybe back in the days those MC loading settings were the standard?
Another odd thing is that the Luxman subsonic filter (15 Hz) produces no sensible change in the sound to my ears. On my Nuova Elettronica preamp instead, the sub filter cuts the frequencies below the 18 Hz mark, and this allows the woofers of my Mission 701 to reproduce bass and mid frequencies with more power.
« Last Edit: March 08, 2012, 01:19:57 PM by lshin80 »



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