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Most Greedy Boy, of them all... or (there is no) DEFiSIT of Papa's Koans
Most Greedy Boy, of them all... or (there is no) DEFiSIT of Papa's Koans
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Old Yesterday, 05:43 AM   #321
generg is offline generg  Germany
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Most Greedy Boy, of them all... or (there is no) DEFiSIT of Papa's Koans
Quote:
Originally Posted by cwtim01 View Post
In that case the 2 devices with higher Vgs are best.

But then, there is a way described here, which overcomes the differences and offer much more freedom.

By the way, when my Lockyz was still alive, I often controlled the Vgs via a 9V battery and 10k pot, this will leave much more voltage headroom for the measurements.
Ha, that's it!

THX
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Old Yesterday, 05:08 PM   #322
generg is offline generg  Germany
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Most Greedy Boy, of them all... or (there is no) DEFiSIT of Papa's Koans
Quote:
Originally Posted by generg View Post

..........

May I add, I am really a bit embarrassed that SIT-3 can go to the same level.

A PP with a Sit for the pos wave form and a mosfet for the neg part.

How can the wonderful sound of a SIT be there when only the left ear hears the SIT.....



I have no doubt that SIT-3 sounds wonderful!
But I do not understand it or I can not explain it.
Friend Peter R. alias "pr" read these lines and answered my in a personal mail telling me that not one ear is hearing the SIT and the other the Mosfet....



But...look his friendly and helpful answer I translated with Google, so all faults due to Google....

"If I understood correctly, you wrote in DiyAudio that the DEF is a mystery. What is the puzzle? May I help?

The MOSFET has a high-impedance drain line, as you can see in the Vds / Id diagram
on the horizontal characteristic (IRFP9240, but not the IXYS MOSFETs):
You can vary Vds a lot, but Id hardly changes, typical pentode characteristics.
The SIT has a low-resistance drain line, which increases Uds / Id characteristic.
This means that changing Vds, Id changes, what is a kind of feedback.
So: The MOSFET has virtually no negative feedback, its Vds is almost arbitrary, the SIT has a negative feedback.
So the SIT responds to the non-linearities of the MOSFET, but the MOSFET does not respond to that of the SIT.
Long story short: the SIT dominates the behavior of the DEF with its character policy."


Wonderful Peter, both ears will hear the SIT!

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Last edited by generg; Yesterday at 05:13 PM.
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Old Yesterday, 06:33 PM   #323
Zen Mod is online now Zen Mod  Serbia
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Most Greedy Boy, of them all... or (there is no) DEFiSIT of Papa's Koans
Funny Gerd

what I posted here : Most Greedy Boy, of them all... or (there is no) DEFiSIT of Papa's Koans

Click the image to open in full size.

red - current through 8R load
green - current through mosfet (IRFP9140)
blue - current through PapaSit

that's probably of same seriousness as Monty Python's Flying Circus - World's Funniest Joke



(yup, I know - nobody is taking serious pretty much nothing I'm writing ............ )
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Last edited by Zen Mod; Yesterday at 06:36 PM.
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Old Yesterday, 06:35 PM   #324
generg is offline generg  Germany
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Most Greedy Boy, of them all... or (there is no) DEFiSIT of Papa's Koans
Quote:
Originally Posted by Zen Mod View Post
Funny Gerd

what I posted here : Most Greedy Boy, of them all... or (there is no) DEFiSIT of Papa's Koans

Click the image to open in full size.

red - current through 8R load
green - current through mosfet (IRFP9140)
blue - current through PapaSit

that's probably of same seriousness as Monty Python's Flying Circus - World's Funniest Joke

I thought it was ART!

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Old Yesterday, 06:57 PM   #325
BeardyWan is online now BeardyWan
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Hi Generg,

Thanks for posting that: The mosfet is largely invariant (pentode), so the SIT dominates the response of the amplifier to any input.

Doesn't it matter that the SIT waveform can look so gnarly?
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Old Yesterday, 07:02 PM   #326
Zen Mod is online now Zen Mod  Serbia
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Most Greedy Boy, of them all... or (there is no) DEFiSIT of Papa's Koans
that's at clipping

point is that PapaSIT and mosfet are working antiphase
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Old Yesterday, 08:48 PM   #327
generg is offline generg  Germany
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Most Greedy Boy, of them all... or (there is no) DEFiSIT of Papa's Koans
So that is the SITuation..... :--))

Seems I have no P channel IRFP9240 Mofets that have the same data as my SITs. They need all a higher Vgs for 1.5A.
So the method Antoinel suggested will not work, is it right that in his case the R084 had the higher Vgs and therefore he could reduce the voltage for the P MosFET?
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Old Yesterday, 11:26 PM   #328
cwtim01 is offline cwtim01  Hong Kong
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The Lockyz measures the devices cold.

I would suggest you to try mounting both FETs onto a heatsink, measure manually (give time for them to heat up and stablize) and see what you'll get. The Vgs required for the 9240 to reach the target current will drop quite a bit after heating up.
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