Semisouth SJEP120R100 Power Loss - Page 7 - diyAudio
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Old 2nd March 2013, 08:06 PM   #61
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In what way so you think leakage will affect performance other than obvious need to lower gate resistor value?
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Old 2nd March 2013, 09:09 PM   #62
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You need to drive the gate with a low impedance source.
The gate resistor is not the issue.


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Old 2nd March 2013, 09:27 PM   #63
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Forgive me. It is not the gate resistor that had to be minimal, it is the pull down resistor at the input. In the F6 thread, he recommended 10-12K as max, due to leakage. I can only assume that this is to limit the the affect of that resistor interacting with leakage of SSr100. I understand higher capacitance requires greater drive current, just don't understand how leakage plays into the equation.
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Old 2nd March 2013, 09:45 PM   #64
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Why not ask Nelson at the F6 thread ?


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Old 2nd March 2013, 09:54 PM   #65
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Quote:
Originally Posted by buzzforb View Post
..... leakage plays into the equation.
it's having everything with impedance of biasing apparatus , same as with impedance of (AC , what else ) modulation aparatus ;

just imagine gate leakage as small current sink and what's then happening with voltages you brought to it ; and - what's most tricky part - that current sink isn't exactly constant

whatever - I'm not loosing my sleep too much over it , neither with matching issues

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Old 2nd March 2013, 10:02 PM   #66
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Thanks ZM. Simple enough even for my short circuit.
I am exploring the Yfs thing because I may choose to run no degeneration, so it becomes a part in THD spectra....I think
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Old 3rd March 2013, 01:01 AM   #67
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Not sure matching is that big a deal either, but fwiw, I got mine from teabag and they were pretty close Vgs matches (no they're not curve matched) .... Perhaps EUVL has a particularly large but diverse batch.
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Old 3rd March 2013, 09:45 AM   #68
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How close is close ? Did you check Vgs on all of them ?

Shame SS went belly up (though predictable from the onset), their latest R055 TO220's looked interesting, better make the most of them.

(btw,Buzz,the message was not about intellect. This place is a gathering of individuals who enjoy sound, and the technical side of audio. Instead of embracing the shared features, quite a few rather focus on what sets them apart, to broadcast their superiority. Looked closer, often more is shared in common. Sometimes it's a cat/dog, a liking for wine/food, or a cheap vampire flic. On the outside, difference can be a million bucks or a PhD apart)
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Old 3rd March 2013, 10:49 AM   #69
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I do have some matched pairs and quads of Semisouth.

But when building my J2-inspired amp, I did not get the results I wanted with the matched ones. Seemed matching for Vgs was not enough....
Out of frustation I took a matched pair and 4 random unmatched Semisouth.

This 6 transistors gave me 6*5 = 30 different combinations for upper and lower half in one F6/J2 channel.
I measured all 30 combinations for THD, 2nd, 3rd, 4th and 5th harmonic distortion.

Those pairs, that gave me the results I wanted, were not the pairs with best matching !

(yes, that is totally stupid approach, but it worked for me )
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Old 3rd March 2013, 10:54 AM   #70
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Thanks Jacco. I know you we're only trying to help. I'm just thick like that, but do agree about the salt, sugar, and chile paste.

BTW, if its a million, we could resolve that seperation. If a PHD, then too bad, cause all I have is THD.
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