Luxman L58A / 2SK163-2SJ44?

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K

KJ2005

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Joined 2008
jechentau said:
no, i do not have such amp (so offtopic perhaps), however as i peered over the schematic i noticed those double series diodes as reference for the vartious ccs'es (or so it appears to me) and i already wondered of this 2v8 zener i have (unrelated to such amp) is just 4x0,7V forward junctions in series (say 4x 1n4148 in a black thinlead ge-diode glass casing) however i am sure it is a silicon device, because it is a "B" device (silicon).
what is the voltage of the reference diodes in the luxman amp btw?
Click to expand...

- Can't find any voltage messurements on the scanned L58A manual page, and I have only repaired the regulated psu for the driver board, resoldered most of the power board - and the L58A sounds just nice. I don't want to change the used components in L58A from around 1982 , nor the original design made by Luxman.

The question no. one is whether it is possible to find substitutes for 2SK163-2SJ44? I think the silke soft highrange reproduction is generated by the inputfets??

Like Mr. Wahab and my friend pointed out, the design of the L58A power stage is good!

The question to you engineers:

"Is it possible to make some minor changes in the L58A input stage design in a way that we keep the sonic sound quality , and at the same time adds a little more drive power to the output stage( 2 pairs of 2SJ50/2SK135 respectively 2SJ162/2SK1058)?"

I might have a burned out M150 for that experiment!

rgds
 
K

KJ2005

Member
Joined 2008
wahab said:
The L58 has some drawbacks...
first, the power amp stage has a very high gain
of about 120..I suppose that it allow for preamp
circuits to work with low gain and reduce distorsion
of these first stages, but then, the power stage
lose some available feedback to reduce THD..

Second, the power mosfets drivers work at low current,
typically about 3 mA , wich is not enough...

Third, it seems that the cascoded differential stage work
with a relatively high current , so the bjt cascodes have
to dissipate something like 250mW each, wich is too much
for the 2SA872/2SC1775 ....

All in all, it s a pity, since the general design ideas are
fairly good but the practical implementation is not up
to these ambitions...
Click to expand...

- Seems as if you have experience with similar designs like the L58A? The power mosfet drivers may work by too low current, but I can assure you that the power mosfet gets fairly hot within one hour of drive.

Like I asked above: Is it possible to make some changes in order to optimize the L58A driver - and power stage design?

If this change of the L58A design becomes too complicated, I will have to stay with the M100 design , from 1982 with the BF760/BF757 drivers - not quite as good as the L58A in sound reproduction, but still better than many amplifiers with bipolar power stage.

rgds.
 
tiefbassuebertr

tiefbassuebertr

Member
Joined 2005
tiefbassuebertragung.de
KJ2005 said:
I have just bought a very nice Luxman L58A still working - But , the circuit for the amplifier part showed, that Luxman for the input differential stage has used 2SK163 and 2SJ44 from NEC.

It is possible to buy the 2SK163 in Europe but impossible to find the complementary 2SJ44.

Does anyone know if there is a substitute pair of fet's available with the approx. same spec's?

Have just bought the output fet's - the original were 134/49 but the 2Sk135/2SJ50 bought takes 160V instead of the original 140V.

Any help would be appreciated.

Rgds.
Kim Hansen
Denmark
Europe

Please find some vintage Luxman amps at: TUBEAMP and find the link to "Skysite"!
Click to expand...

2SK163/2SJ44 datasheets now available from RENESAS:
http://www2.renesas.com/maps_download/pdf/TC-5409.pdf
http://www2.renesas.com/maps_download/pdf/TC-5466.pdf
http://www2.renesas.com/maps_download/document_en?litcode=TC-5466
 
K

KJ2005

Member
Joined 2008
tiefbassuebertr said:
2SK163/2SJ44 datasheets now available from RENESAS:
http://www2.renesas.com/maps_download/pdf/TC-5409.pdf
http://www2.renesas.com/maps_download/pdf/TC-5466.pdf
Document Download | Search | FAQ / Support | Renesas Electronics
Click to expand...

Hi tiefbassuebertr ,

Thank you very much for the 2SK163/2SJ44 datasheets.

While I am making a "non feedback" DC amplifier with bipolar transistors just now , I am still thinking of my mosfet project for which I have bought 20 pcs. of the 2SJ50/2SK135 original Hitachi output fets. I don't want to change my L58, Luxman, but I would very much like to built a input stage with the mentioned 163/44 fets. Unfortunately NEC don't make them any more.

Do you have any suggestions? - or somewhere to find a new old stock?

Kind regards
Kim H.
 
tiefbassuebertr

tiefbassuebertr

Member
Joined 2005
tiefbassuebertragung.de
KJ2005 said:
Hi tiefbassuebertr ,

Thank you very much for the 2SK163/2SJ44 datasheets.

While I am making a "non feedback" DC amplifier with bipolar transistors just now , I am still thinking of my mosfet project for which I have bought 20 pcs. of the 2SJ50/2SK135 original Hitachi output fets. I don't want to change my L58, Luxman, but I would very much like to built a input stage with the mentioned 163/44 fets. Unfortunately NEC don't make them any more.

Do you have any suggestions? - or somewhere to find a new old stock?

Kind regards
Kim H.
Click to expand...

I am not sure, what means "non feedback DC amplifier". I real life such amps don't exist.
Mean you perhaps an amplifier without NFB (negative feed back/global feedback)?
Other variations are
- an amplifier with global feedback only inside of two voltage gain stages (front end resp. diff amp + VAS stage), i. e. the power buffer push pull stage is outside of this loop.
- an amplifier with global feedback only inside of one voltage gain stages (i. e. without diff-amp or folded cascode or diff-amp with unity gain).

Please send me your simplefied schematic to know exactly, what for you is a "non feedback DC amplifier" and let me know your wanted idle current through the output stage (classA or A/B).

Better available for old NEC replacement are various types from Toshiba:
Junction FETs (Single) | MOSFETs | TOSHIBA Semiconductor Company
and RENESAS
http://www2.renesas.com/discrete/en/products/transistor/function/jfet/lownoise.html
http://www2.renesas.com/discrete/en/products/transistor/function/jfet/general.html
http://www2.renesas.com/discrete/en/products/transistor/function/jfet/highsens_lownoise.html
http://www2.renesas.com/discrete/en/spice/mos/spice_2sj.html (Spice Models)
 
Last edited:
M

moray james

Member
Joined 2003
morayjamescables@yahoo.com
My friend John Wright at Museatex just got an L58A and plans to refurbish it shortly. You might contact him as he does design work. The Museatex amplifiers in the STR and MTR range all use the same Diamond buffer front end design as used in the Luxman. John modifies the Meitner amps with a cascode second stage as in the Luxman L58A. You can contact John via the Museatex web page. Regards Moray James.

:: museatex ::
 
K

KJ2005

Member
Joined 2008
tiefbassuebertr said:
I am not sure, what means "non feedback DC amplifier". I real life such amps don't exist.
Mean you perhaps an amplifier without NFB (negative feed back/global feedback)?
Other variations are
- an amplifier with global feedback only inside of two voltage gain stages (front end resp. diff amp + VAS stage), i. e. the power buffer push pull stage is outside of this loop.
- an amplifier with global feedback only inside of one voltage gain stages (i. e. without diff-amp or folded cascode or diff-amp with unity gain).

Please send me your simplefied schematic to know exactly, what for you is a "non feedback DC amplifier" and let me know your wanted idle current through the output stage (classA or A/B).

Better available for old NEC replacement are various types from Toshiba:
Junction FETs (Single) | MOSFETs | TOSHIBA Semiconductor Company
and RENESAS
Low noise | J-FET | Transistors | Discrete | Products | Renesas Electronics
For general use (general purpose) | J-FET | Transistors | Discrete | Products | Renesas Electronics
High sensitivity and low noise | J-FET | Transistors | Discrete | Products | Renesas Electronics
2SJ Series | SPICE Models | Discrete | Products | Renesas Electronics (Spice Models)
Click to expand...

Might give you an answer later - need to ask for any copyright.
 
K

KJ2005

Member
Joined 2008
moray james said:
My friend John Wright at Museatex just got an L58A and plans to refurbish it shortly. You might contact him as he does design work. The Museatex amplifiers in the STR and MTR range all use the same Diamond buffer front end design as used in the Luxman. John modifies the Meitner amps with a cascode second stage as in the Luxman L58A. You can contact John via the Museatex web page. Regards Moray James.

:: museatex ::
Click to expand...

Thank you - I shall ask him later.

Rgds
Kim
 
K

KJ2005

Member
Joined 2008
mlloyd1 said:
my japanese is not so good :eek:
heres an english version of the 2sj44 datasheet:
Download | Datasheet Archive

mlloyd1
Click to expand...

Yes...easyer to understand in an english version. ....seems to be more than difficult to find several pairs of the mentioned fet's ( enough to match some of them).
....Did not had the time to search for replacements that could take the same voltage - and even with the same good sonic sound - if there are any??

... a lot of projects for the moment.

Kim
 
K

KJ2005

Member
Joined 2008
tiefbassuebertr said:
I am not sure, what means "non feedback DC amplifier". I real life such amps don't exist.
Click to expand...

Well ..... besides small local feedback..... "The End mk.II" comes as close to a "NO FEEDBACK" amplifier as possible.

The 1990 schematic is shown by kind permission of the man who designed the amplifier Mr. L.H.Clausen , and the company that owns the copyrights for "The End mkII", 800XE power modules and more.... the company LC Audio, Denmark.

Find "The End mk.II" schematic at: leakstereo20

...and the button "The End circuit"

rgds.
 
tiefbassuebertr

tiefbassuebertr

Member
Joined 2005
tiefbassuebertragung.de
KJ2005 said:
Well ..... besides small local feedback..... "The End mk.II" comes as close to a "NO FEEDBACK" amplifier as possible.

The 1990 schematic is shown by kind permission of the man who designed the amplifier Mr. L.H.Clausen , and the company that owns the copyrights for "The End mkII", 800XE power modules and more.... the company LC Audio, Denmark.

Find "The End mk.II" schematic at: leakstereo20

...and the button "The End circuit"

rgds.
Click to expand...

I don't find the schema about
leakstereo20
but I think, you mean this amp topology:
leakstereo20
L C Audio Technology/The End Millennium (predecessor)
this is indeed called "No Feedback Amp" from Mr. L.H. Clausen.
Actually Mr. Clausen means "No Global Feedback Amp", because there are three independend feedback-loops:
A: Voltage gain stages (open loop gain = closed loop gain):
1) Serial feedback R1+2
2) Serial feedback R32+32
B: Power Buffer stages (pre-Driver Buffer + PP Sziklai Darlington)
very high hfe/ typical combinations of local serial feedback from a power follower/local NFB of a Sziklai-Darlington.

If you check only the power buffer of this topology by changing the output and GND, you will see the amount of the open loop gain factor.

At my opinion this design is to prefer for applications in the upper frequency range (> 1000 Hz), while NFB designs is to prefer for the frequency range below 1000 Hz. Full range (single amp) applications, used from the most music lowers, still a compromise between clear and tight bass and smooth/musical midrange/height (voices e. g.).

Presently I think about an evaluation amp PCB design, where I can realize (e.g. through jumper change) Mr. Clausen's amp design so as various NFB amp designs for directly comparable on various speakers/complex loads. So I can more talk about the pros and cons. But at whole I get still too much posibilities of combinations.
 
Last edited:
K

KJ2005

Member
Joined 2008
tiefbassuebertr said:
I don't find the schema about
leakstereo20
but I think, you mean this amp topology:
leakstereo20

this is indeed called "No Feedback Amp" from Mr. L.H. Clausen.



But at whole I get still too much posibilities of combinations.
Click to expand...


... think I wrote press the "The End circuit" button.

.... Also wrote small local FB used at the mk.II version.

forget all about the circuit possibilities... think that one has to keep both legs on the ground, and follow whatever long experience has told you.

The sonic sound of the last analog amplifier Millenium , in my opinion, can't quite compete with the "The End mk.II and mk.III" version - and don't tell anyone about a choice between a tight bass and musicality in mid-and high frequences when talking "The End mk.II and III" ..... you get both when you built these amplifiers.......say - built very accurate with matched transistors!!

You need to built at least 10 of these amplifiers before it is possible come up with any statements about their musicality.
 
tiefbassuebertr

tiefbassuebertr

Member
Joined 2005
tiefbassuebertragung.de
tiefbassuebertr

tiefbassuebertr

Member
Joined 2005
tiefbassuebertragung.de
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