New Naim Output Transistors

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#21
how come you are so keen to BJT output tranies, should it not be lateral FET's to make you post, or are we seeing Ayre with BJT's in the output soon?
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................................only the Shadow knows!

Jam
 

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#22
NAP250 uses -001 transistors in TO3 package (a special BUV20 made by Semelab)

NAP500 uses -007 transistors in TO3 package (also made by Semelab)

NAP150 uses SANKEN 2N2922 like the discontinued NAP140


quote Julian Vereker (in HIFI+ #4/99) about the development of the NAP250:

"... I wanted a transistor which was very fast (rather than necessarily linear), without any storage time especially at low currents, and I wanted it to turn off at low currents. ..."
 
#26
lohk said:
NAP250 uses -001 transistors in TO3 package (a special BUV20 made by Semelab)

NAP500 uses -007 transistors in TO3 package (also made by Semelab)

NAP150 uses SANKEN 2N2922 like the discontinued NAP140
Click to expand...

Thanks for the info. Semelab is a small UK-based foundry that is willing to do specials and custom parts. (They are the ones who make the Exicon and Magnatec lateral MOSFETs.)

According to the Naim website:

http://www.naim-audio.com/products/nap250.html

"The NAP 250 uses the same 007 transistors that were custom-designed for the NAP 500. These outstanding components each provide up to 80 amps and 350 Watts, negating the need to use parallel pairs of transistors (which always have a negative effect on sound)."
 
#27
That's a different NAP250 to the one pictured up-thread, FWIW. Only the name(!) remained the same.

I have a mid-70s NAP250, which is a similar design to the one pictured up-thread but a different case style and circuit arrangement and that's fitted with 8 BDY58s. FWIW.

Paul
 
#28
Naim changed the output transistors for the 250 in the late 70ies (aprox.) from BDY58s to the mentioned 001 propriate designs. Since then the classical 250 used this transistor. The new 250 is another story, using different regulators and amp inputs AFAIK.
 
#29
I have very good experiences using the Cyrus PT7 (TO-220, BUV28?) and PT77(TO-247, another switching transistor?) in Naim clones. The smaller amps can use the BD911 or like other smaller Naim amps the BD743 (the NAIM NA-005). The older version of the NAP110 used the BUV20.
 
#32
Semelab lateral MOSFETs

Charles,

> Semelab is a small UK-based foundry that is willing to do specials and custom parts. (They are the ones who make the Exicon and Magnatec lateral MOSFETs.)

Have you tried any of their lateral MOSFETs ?
Any that you might care to recommend for power amp output stage ?

(Am currently using 2SK1529.)

Thanks,
Patrick
 
#33
Their lateral MOSFETs are improved versions of the original Hitachi parts. If you have an old amp with the long-discontinued Hitachi TO-3 lateral MOSFETs, you can directly replace them with the Semelab (Exicon, Magnatec) parts. Also, the P-channel parts are superior to the Hitachi parts, with a much better match to the N-channel parts. (This is with respect to the temperature coefficient, the transconductance, and the triode vs. pentode shape of the characteristic curves.)

The 2SK1529 is a vertical MOSFET from Toshiba. The vertical parts have a much higher (and more non-linear) input capacitance than do the lateral parts. However the lateral parts have a lower transconductance, so you would generally have to parallel several of them.
 
#35
Charles Hansen said:
Their lateral MOSFETs are improved versions of the original Hitachi parts. If you have an old amp with the long-discontinued Hitachi TO-3 lateral MOSFETs, you can directly replace them with the Semelab (Exicon, Magnatec) parts. Also, the P-channel parts are superior to the Hitachi parts, with a much better match to the N-channel parts. (This is with respect to the temperature coefficient, the transconductance, and the triode vs. pentode shape of the characteristic curves.)
Click to expand...


How about those TO3P plastics 2SJ162/2SK1058 from Renesas(former Hitachi), are they improved in anyway comapring to their old predecessors TO3 2SJ50/2SK135, I how wondered for long time have the improved processes with todays technology improved anything on their succecors?

Cheers Michael
 
#36
Ultima Thule said:
How about those TO3P plastics 2SJ162/2SK1058 from Renesas(former Hitachi), are they improved in anyway comapring to their old predecessors TO3 2SJ50/2SK135, I how wondered for long time have the improved processes with todays technology improved anything on their succecors?
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No, just the same part in a different package. Not a bad part, but the Semelab parts are a little bit better.
 
#37
Talking MOS_FETs and semicomplementary output stages.

I would go for something like the IXFR150N15 from IXYS.
The device have electrical isolation (AlO3 back) thus reducing
the total thermal resistance to the cooler. Ususally it boils down
to thermal issues in the end when you try to squeeze the last
few watts out of a package.
Still this is a fairly standard TO247 package. If one likes more oddball packages which is fine for low volume production
like DIY there are unlimited options of ultra high power devices.

Regards / Mattias
 
#38
Charles,

> The 2SK1529 is a vertical MOSFET from Toshiba.

According to Toshiba, they call it pi-MOS. And it looks more like lateral than vertical to me. See my previous post :

http://www.diyaudio.com/forums/showthread.php?postid=661146#post661146

Also the Ciss is much lower than e.g. an IRFP240 :

IRFP240 1300p
2SK1529 700p
2SK1058 600p

> you can directly replace them with the Semelab (Exicon, Magnatec) parts.

Does Semelab offer them directly ?

Would you have a part number for an 2SK1058 equivalent, for example ?


Thanks,
Patrick
 
#39
this is another trick NAIM uses to sell their overprised products !
theres nothing wrong with paralelling transstors! in fact thats much better then using a single pair !
bigger transistors = slower
when paralelling u can use faster and smaller transistors and achieve high damping factors .


next thing they gonna say is "we are using one big cap on the power supply , rather then many small ones 🙄 "
 
#40
sss said:
this is another trick NAIM uses to sell their overprised products !
theres nothing wrong with paralelling transstors! in fact thats much better then using a single pair !
bigger transistors = slower
when paralelling u can use faster and smaller transistors and achieve high damping factors .


next thing they gonna say is "we are using one big cap on the power supply , rather then many small ones 🙄 "
Click to expand...

So I take it you have done listening tests with single versus
multiple OP devices of same type same amp etc?



Cheers,

Terry
 
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