Choosing an ouput pair

[Sergimm]

I'm restoring a Luxman L1 (thread), and I want to replace the current output transistors, which are not original. I am far from understanding all that's implied on pairing these kind of transistors, so I've made a list of potential replacements:

2SA1135/2SC2665 (Original as specified on the SM)
2SA1106/2SC4467 (Currently-and haphazardly-installed)
FJA4210/FJA4310
2SA1694/2SC4467
NJW1302G/NJW3281G

I've made a table to make it clearer:



Which pair of output transistors would you install?

 

[Tom B]

I would go for the 2SA1694/2SC4467, as long as you buy them from a reputable place. The others are quite a bit heavier than the originals, and no need to go that high. Transition Freq for originals is 10mhz, and the recommended pair show as 20Mhz which should be OK. See if original Sankens are available through a place like Mouser or other reputable supplier.

 

[ConradH]

Others probably know more but I'd want to see curves for hfe vs current. If the beta droops, the THD will go up with lower impedances. Definitely no slower devices than the original, if possible.

 

[Sergimm]

Others probably know more but I'd want to see curves for hfe vs current. If the beta droops, the THD will go up with lower impedances. Definitely no slower devices than the original, if possible.

Thanks! That sounds really interesting. I think you are referring to the graphs like the one below (that’s the one for 2SA1694). How do I distinguish the “speed” concept you are referring to in this kind of graph?

 

[Tom B]

Speed is the parameter of Ft as shown in the transistor specs

 

[Sergimm]

Speed is the parameter of Ft as shown in the transistor specs

Right of course, I though Conrad’s comment about speed was related to his first sentence about the graph.

 

[Binkman]

Definitely no slower devices than the original, if possible.

Ditto. IMO Luxman can be a bit sonic sensitive so keep orig. specs of components Also be aware of cold solder.aged joints for the drivers.

 

[Sergimm]

I would go for the 2SA1694/2SC4467, as long as you buy them from a reputable place. The others are quite a bit heavier than the originals, and no need to go that high. Transition Freq for originals is 10mhz, and the recommended pair show as 20Mhz which should be OK. See if original Sankens are available through a place like Mouser or other reputable supplier.

Yeah it seems it is the choice closest to the original specs and Digi-Key still carries them