LL1660, a match for SK135/J50?

[Jay]

I don't remember that hybrid amp that catched my attention. If I'm not mistaken, it is designed by Guido Tent, using modern MOSFET, a 100mA Lundahl, and a tube.

This amp has a "bad" measurement for distortion (like many transparent tube amps). I don't remember if this amp has version that using old Hitachi MOSFET, but that is exactly what I want:

To build the best sounding amplifier from Hitachi K135/J50.

What I want to know is whether I can use the old Hitachi as direct replacement for the newer MOSFET in that schematic, without doing serious harm to the Hitachi (I'm willing to experiment even without sufficient knowledge, but hopefully I can get some help )

Another one is whether LL1660 of the higher current rating can be used without much different (Because I think the higher one can be re-used for different projects)

[peranders]

Notice also that K135/J50 differs depending of how old they are. My first amp did deliver 285 watts and when I changed mosfets to newer ones I got 385W! The newer fets had substantially lower Rdson.

BTW: I have approx. 30 pairs left of those "newer" ones and they are forsale.

[Upupa Epops]

To Per - Anders : The same types ? As I know, Hitachi was declared the same parametres all the time .

[peranders]

Indeed but they had a lot less than 1.7 ohms the later transistors, in fact under 1 ohms!

[ekaerin]

Hi,
Also watch out for the threshold voltage. The Hitachis start conducting
from Vgs=0. Blinded by the devices I use at work I had to experience
this the hard way.

/ Regards / Mattias

[JFG67]

Originally posted by Jay

To build the best sounding amplifier from Hitachi K135/J50.

What I want to know is whether I can use the old Hitachi as direct replacement for the newer MOSFET in that schematic, without doing serious harm to the Hitachi (I'm willing to experiment even without sufficient knowledge, but hopefully I can get some help )

Hello,

One can know the reference of this recent transistor Hitachi ?
If they is the K1058/J162 they are the same chips inside as the K135/J50.
Can one see this diagram of amplifier ?


@ + Jean-François

[analog_sa]

100mA Lundahl

A 1660 at a 100mA?!

[Ultima Thule]

Originally posted by peranders
Indeed but they had a lot less than 1.7 ohms the later transistors, in fact under 1 ohms!

Hi Per-Anders,

do you know from what date the 2SJ50 and 2SK135 got lower Rds-on?
What's the serial number you have on yours?
Is it possible to recognize the diffrence visually on the transistor package?

mvh Michael

[peranders]

I have no idea how the date code works but from my own experience I can say that the first amp was built 1984 and the second one 1989.

[Jay]

That's very interesting what you have found with the Hitachi, Peranders.
I'm not surprised myself if that is true.

Here is the website for the schematic:

http://www.homestead.com/whaan/files/page3.html

It's not 100mA, Analog_sa, but 10mA. The higher version one is 18mA if
I'm not mistaken. The one used in the Euridice preamp (but with single
secondary I guess). Other main components are 5687, LL1660/10,
Magnatec BUZ900P/905P.

I'm going to use parallelled K135/J50 for the output. That is if I got
the green light