The little Luxman L-1... and a quick recap/upgrade

[Karl vd Berg]

Two days ago I collected this little amp and despite the fact it is an entry level unit, it's nice and sounds very good.

 

[Karl vd Berg]

The amp was quite warm even with volume completely down, so bias had to be checked. The "idle current" was giving something around 28mA (L) and 25mA (R) instead of the 50mA for both channels, according to the manual service.

The transformer was quite warm and a couple of resistors in the PS were VERY HOT. These are 150 ohms rated 2W put before the Zener for the lamps.

This might be an unit made around 1979/80 without voltages selector.

The transformer's primary windings for 220V had a secondary winding for nearly 29Vac (forgot a picture for that). I don't know how the stock cap (85*C) could handle that for such long time (since January 1995).

The red for 240V was wired and secondary voltage is now ~26Vac. Thansformer is cooler.

 

[Karl vd Berg]

Quick recap. There are 21 caps, including the main caps, upgraded to 6,800uF/63V/105*C replaced, plus new rectifiers and the two 150 ohms 2W resistors replaced with 5W ones.

The other caps are of same capacitance but higher voltage rating, except for the one replacing stock C201ab (low leakage, 3rd pic)

 

[Karl vd Berg]

The "loudness" in this unit is indeed too loud! I replaced the two stock mylar 33nF caps with 18nF ones and it is now more balanced with the high frequencies.

Reflow soldering where it is need.

Setting idle current back to 50mA.

 

[Karl vd Berg]

And here we are. Playing cooler...

 

[sqlsavior]

Congratulations, looks nice.

Curious if the sound changed any, and if so, how?

Great pics - thanks for posting!

 

[ryuuoh]

Very nice work and documentation.

 

[Karl vd Berg]

...

Curious if the sound changed any, and if so, how?

Yes, the sound changed. In fact, and I forgot to mention it when posting about "loudness", the low end is more pronounced after replacing the el-caps. I had to change the stock 33nF caps with a lower value for the loudness because low freqs were a bit overhanging. I could even go as low as 10nF or 4nF, but 18nF is ok for the speakers I have and the amp has a good low cut anyway.

I thought I could change the drivers and push idle current up to 75mA, but I'll leave it for now.

Overall, the sound is so far very pleasant, GREAT for FM listening at moderated levels.

 

[Dswankey]

First Luxman?

 

[rlisin]

It's a nice little Luxman. I had a version of this amp made for Quadral, the L-101. Looked like this:

 

[Karl vd Berg]

First Luxman?

Integrated? Yes. I had a nice Lux tuner, the TD-377.

And I can only imagine what other Lux of higher level can do! There's a L-230 in mint condition no far from here...

rlisin, that's a German made unit? :thmbsp:

 

[SoundOfSound]

Nice job! :thmbsp:

Hard to believe they used 35V caps on a 35V rail? :scratch2:

 

[Dswankey]

Congrats!!! Here's some info and a great resource for Luxman information.

http://www.hilberink.nl/codehans/luxman38.htm

http://www.hilberink.nl/codehans/luxman.htm

 

[Karl vd Berg]

That's a very nice site for Luxman gear!!

 

[rlisin]

Not German made, made by Lux Corporation for a German brand.
It's a re-branded Luxman L-1(A). Identical to yours except for the same color buttons and lack of lamps for the source selector switch. And the Quadral logo instead of Luxman of course.

 

[Jody Thornton]

It's a nice little Luxman. I had a version of this amp made for Quadral, the L-101. Looked like this:

I love this sort of entry level stuff (even more than high end). Just simplicity with a touch of class.

 

[Jody Thornton]

Integrated? Yes. I had a nice Lux tuner, the TD-377.

And I can only imagine what other Lux of higher level can do! There's a L-230 in mint condition no far from here...

rlisin, that's a German made unit? :thmbsp:

I had a similar Rotel amp (mine was bought in 2000 with 35-watts/ch, but I can't remember the model number - but it looked identical)

 

[ZOOM]

I suggest you replace the 2SA979 dual transistors in the differential stage with a matched pair of KSA992 transistors with the emitters tied together. Those dual transistors are a common cause of trouble. Plus, you might reduce some distortion by using fresh (and better) transistors.

 

[Alienz]

I had the same problem in my L1 with overheating resistors in the circuit that provides power to the lights, as did a friend of mine in his L-114 which is almost the same design. Replaced them with higher wattage resistors too, I'm not very good at math but some fellow AK'ers calculated that the wattage Luxman used for these resistors really is too low.

 

[Karl vd Berg]

It's a survivor: all these years under 29Vac (230V), the lamps are still good... I bought a new 9.1V Zener (rated 1.3W), but kept the stock one as it still under specs.

I suggest you replace the 2SA979 dual transistors in the differential stage with a matched pair of KSA992 transistors with the emitters tied together. Those dual transistors are a common cause of trouble. Plus, you might reduce some distortion by using fresh (and better) transistors.

Thanks! When I'll place next order they'll be in. Looks like an easy unit to upgrade/tweak.
Outputs are driven by a couple of 2SC1845 which seems good enough for this range of power? :scratch2:

I wonder if this unit is also part of the "Duo-Beta" circuitry from Luxman.
http://www.audiokarma.org/forums/showthread.php?t=109591 (from post #3)