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Old 26th April 2008, 11:59 PM   #451
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Thanks, I didn't think so.
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Old 27th April 2008, 12:03 AM   #452
zinsula is offline zinsula  Switzerland
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Matching P with N MOSFET's will be difficult.
The different Vgs at the operating bias (resulting in offset) can be trimmed.
And the proposed pairs have a rather different transconductance....

Matching will be important if you are paralleling FET's of same polarity, as in the F4.

Tino
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Old 27th April 2008, 12:21 AM   #453
zinsula is offline zinsula  Switzerland
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Talking about the complementary pair....

Wouldn't the FQA17P10 be a much better complement? Looking at the transfer characteristics, I would think so.

100V instead of 200V, thats no problem for these amps (all with 18V secondaries )

The only drawback being the Junction-Case thermal resistance, which is higher (but in my opinion still ok, the junction being 15-20�C higher than the N-Channel part @30Watts per device as in the F5 case).

And in a F4 an absolute no brainer.

My 2 cents..

Tino
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Old 27th April 2008, 01:04 AM   #454
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I'm in for 100 pairs.
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Old 27th April 2008, 03:24 AM   #455
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It will work fine, but if you are tweaking distortion figures by balancing
the JFET/MOSFET gain products, you will find yourself doing so in
random directions with the original parts. If you use the 17P, you
will probably find yourself consistently trimming high on the + side
and low on the - side.
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Old 27th April 2008, 04:58 AM   #456
EUVL is offline EUVL  Europe
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If you go balanced (like the circuit Tino posted a while ago) and match left and right well, then the P-N match becomes less important, as one gets even order cancellation between left and right, in addition to constant current draw from power supply. But then I would be looking at +/- 16V rails (at the expense of somewhat higher capacitance at the FETs) and go for 2A bias per FET. This is my current thinking.

Dennis, very kind of you. Let's see how it goes. If the many interest in Europe, it is easier to order from Digikey.

So far we have :

40 pairs EUVL
100 pairs Jacco
100 pairs yggdrasil
20 pairs Yunick

190 pairs short.

I have opened a new thread at the Group Buy forum :

http://www.diyaudio.com/forums/showt...75#post1494775

Please only post over there if you want to join, and NOT at this thread.


Patrick


Please note that Digikey price is excluding VAT, which is 19% in Germany (and in Holland I think). On top of that, Digikey charges a handling fee of something like 20-20 Euros, and we probably have to have 10% reject calculated in if we want matched quads (2Ns & 2Ps, but probably N-P with different Vgs, depends on what we get). On top of that postage to you (for 100 pairs by Small packet uninsured 7 Euros within the EU, Parcel / DHL insured 17 Euros. It will endup somewhere around Euro 1.50 per pair. Still a bargain.
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Old 27th April 2008, 08:23 AM   #457
EUVL is offline EUVL  Europe
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20 pairs left. Group buy will close today.
First come first serve.


Patrick
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Old 27th April 2008, 08:56 AM   #458
EUVL is offline EUVL  Europe
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Group Buy closed !!

Have a nice weekend,
Patrick
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Old 27th April 2008, 10:57 AM   #459
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Quote:
Originally posted by Nelson Pass
Now I've done it. The F5 isn't even out and some of you will
already be scrambling to build the two balanced versions.
__________________
BOXES for crying out loud
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Old 27th April 2008, 01:05 PM   #460
EUVL is offline EUVL  Europe
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Those who subscribed to the Group Buy :

40 pairs EUVL
100 pairs Jacco
100 pairs yggdrasil
20 pairs Yunick
60 pairs Cfm
30 pairs Zinsula
30 pairs Tazzz
20 pairs Danny_66

Please send me a PM stating :

You full name, postal address, and whether you wish the transistors to be sent insured or uninsured.

http://www.diyaudio.com/forums/showt...54#post1494854

Till now, only Zinsula had mailed & confirmed payment details.


Patrick
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