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Old 6th March 2009, 06:41 PM   #11
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Sometimes higher voltage rails are given to avoid hard clipping problems which I think is the case here, although the voltage needed be so high. Anyway if you looking for high voltage Jfets try these, they on par with the well known toshiba parts and in some respects even better. 2sk223.
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Old 6th March 2009, 06:44 PM   #12
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~50A peak from a pair of Hitachi bipolar power transistors that can't according to their datasheet.

Wowza, must have been some power amp.
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Old 6th March 2009, 06:59 PM   #13
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Quote:
Originally posted by Michael Chua
90V rails, 200W rating = Dynamic Headroom.

Would be wise to double the outputs.

If it were one of those amps that can really put out 400Wx2/8R, and only claims 200 - so that they can claim 3dB headroom and doubling down to 4 ohms (and again at 2) it would have more than any two or four pairs of outputs per channel. More like 6, 8 or even 12 pairs.
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Old 6th March 2009, 07:04 PM   #14
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Quote:
Originally posted by jacco vermeulen
~50A peak from a pair of Hitachi bipolar power transistors that can't according to their datasheet.
Woudn't be the first time.

Quote:

Wowza, must have been some power amp.
Or they needed the smell of burnt carbon resistors to cover up what they were smoking in the engineering lab.
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Old 7th March 2009, 12:26 AM   #15
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From NAD 2400

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Old 7th March 2009, 10:40 AM   #16
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The NAD 2200 would bench at 360W/8R for about a half second (far longer than a musical transient).

If you drove it with a sinewave more than a second, it would shut down the ±93V rails, and just run on the ±60V rails (which is what the 100W long term rating was about).
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Old 7th March 2009, 11:02 AM   #17
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Default thank you all

for your answers and information .....

i would have second thoughts on builting this thing even with a couple more sets of transistors since and since bias will have to be redesigned and of course VI limiters also ....

then just go for DIRTY HARRY BY FOTIOS and all will be just fine

thanks !!!!
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Old 7th March 2009, 12:33 PM   #18
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Quote:
Originally posted by djk
The NAD 2200 would bench at 360W/8R for about a half second (far longer than a musical transient).

If you drove it with a sinewave more than a second, it would shut down the ±93V rails, and just run on the ±60V rails (which is what the 100W long term rating was about).

This would describe a Class G amp http://en.wikipedia.org/wiki/Electro...#Class_G_and_H

FWIW- The new generation of car decks use class H with an internal charge boost (external cap only) for up to 70V for short term.

The TDA1562 is a monolithic integrated 70 W/4 W
Bridge-Tied Load (BTL) class-H high efficiency power
amplifier in a 17 lead DIL-bent-SIL plastic power package
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Old 7th March 2009, 02:58 PM   #19
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Different manufacturers reverse their descriptions of class G and class H.

I use the reference cited in the Wikipedia:

http://www.qscaudio.com/support/libr...rs/amptalk.pdf

And Douglas Self:

Click the image to open in full size.

To retain our sanity, I suggest following the above convention.

Early examples of class G:

http://www.google.com/patents?id=E2k...622899#PPA1,M1

http://www.google.com/patents?id=z-c...772606#PPA1,M1
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Old 7th March 2009, 04:37 PM   #20
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Default god i hate nad amps

all..... but all of them ....

ok !!!! since i had a quiet time this afton i though about making a pcb with the above circuit but with plastic transistors and totally 8 transistors in the out for every board .....

anybody willing to try it is very welcome and i also have gerber export for it ....

please notice that this isa demo and it is possible that i ve made mistakes that i couldnt find with double checking !!!!!

there you go
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