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Old 20th November 2005, 07:41 PM   #11
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BTW, look at new IRF, there you can find many 300-350 W ones...
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Old 20th November 2005, 08:17 PM   #12
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Quote:
Originally posted by Upupa Epops
Why do you mean, that paralleling have negative impact in sound, Charles ? Have you some proofs for this statement ?
I didn't say that -- I was just quoting from the Naim website.
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Old 20th November 2005, 08:36 PM   #13
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There have always been a handful of specialty semiconductor manufacturers who have built much larger discrete bipolar power transistors,
usually in metal and plastic modules with screw terminals. Alas,
my middle-aged brain refuses to recall a single name now! Often
these are multiple devices soldered in parallel on a heat spreader
that is bolted to an appropriate heatsink.

However, for the right price, the semiconductor die can be made
much larger for increased current and power dissipation. These are
usually employed in motor controllers and the like, and seldom
make it into consumer electronics.

An advantage is that two large devices can replace many paralleled
devices, and save some money on the simplified assembly. I can see
where Naim could have commissioned a special part for their design
at reasonable cost (to them), when manufactured in the thousands.
I guess my question is how fast these transistors would be.

But I'll continue to use paralleled transistors, thank you; far cheaper
and more available.

I had a look at Apex Microtechnology's site, but it appears they are
into large power ICs rather than discrete semiconductors.
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Old 20th November 2005, 08:44 PM   #14
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Yes, transistors for locomotives, it is righ thing, which catapult this firm into hifi heaven... ( but still in quasicomplementary heaven... )
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Old 20th November 2005, 10:31 PM   #15
dimitri is offline dimitri  United States
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Quote:
some to-3 trannsistors can dissipate 350W
80A BUR51, BUR52 from ST, 60A BUX20 from Semelab
hFE=20-100, transition frequency 10Mhz

NAP-250
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Old 20th November 2005, 10:40 PM   #16
jam is offline jam  United States
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Dimitri,

You maigt be right..........................but look at the maximim base current, you probably need an output device to drive these things.............

Regards,

Jam
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Old 20th November 2005, 10:42 PM   #17
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More dissipation = better sound = promotion blables...
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Old 20th November 2005, 10:55 PM   #18
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Quote:
Originally posted by jam

You maigt be right..........................but look at the maximim base current, you probably need an output device to drive these things.............
That's easy to fix. These babies from ON are 300 W Darlingtons with hfe of min 400 @ 50 A Ic

www.elfa.se/pdf/71/07105208.pdf
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Old 20th November 2005, 11:15 PM   #19
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Quote:
Originally posted by dimitri
NAP-250
OK, Dmitri, you've solved the mystery. The NAP-250 uses the "007" transistors, and they are clearly TO-3 packages.

I'm used to using TO-264 packages, which stop at about 15 A and 230 W for modern high-speed designs. I was surprised to hear about devices with 5x the current and over 50% power dissipation, but as you and others have pointed out, the Naim transistors are not so unusual.

Thanks for your input, everybody!
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Old 21st November 2005, 01:12 AM   #20
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Quote:
Originally posted by dimitri


80A BUR51, BUR52 from ST, 60A BUX20 from Semelab
hFE=20-100, transition frequency 10Mhz

NAP-250

Dimitri,

you have e-mail!


Charles,

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?

Cheers michael
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