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L'Amp: A simple SIT Amp
L'Amp: A simple SIT Amp
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Old 26th March 2012, 06:41 PM   #821
generg is offline generg  Germany
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L'Amp: A simple SIT Amp
ha, ha, thanks for the applause.....

but of cause I do not know why it is as it is.....


and I still do not know why Papa puts so many caps near to the Vishay resistors in SIT-1...... nobody any idea?

maybe he loves caps of tea?
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Last edited by generg; 26th March 2012 at 06:44 PM.
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Old 26th March 2012, 06:45 PM   #822
ra7 is offline ra7  United States
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L'Amp: A simple SIT Amp
Could it be the output cap?
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Old 26th March 2012, 06:48 PM   #823
Tea-Bag is offline Tea-Bag  United States
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L'Amp: A simple SIT Amp
Well then, how does it sound to R100 only amp?
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Old 26th March 2012, 06:57 PM   #824
Zen Mod is offline Zen Mod  Serbia
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L'Amp: A simple SIT Amp
Quote:
Originally Posted by generg View Post


and I still do not know why Papa puts so many caps near to the Vishay resistors in SIT-1...... nobody any idea?

maybe he loves caps of tea?
convenient place for mucho PSU caps (and possibly just few output ones) - sounds logicall ?

2 reasons for that - poor PSRR of circuit itself , empty pcb if you leave just resistors there

edited - few important words swallowed , probably .... usual ZM's brainfart
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Last edited by Zen Mod; 26th March 2012 at 07:06 PM.
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Old 26th March 2012, 07:54 PM   #825
generg is offline generg  Germany
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L'Amp: A simple SIT Amp
yes Zen Mod and ra7,

that is the most logical and simplest answer.....

and I do not see CRC in the PSU so more caps are useful....!

but my intention is not to discuss Papas SIT here primarily, I was more interested if the picture gives us an advice to "better" our thick film resistor solution......sounding not so dark....I repeat, I understand now the people doing "Bulb Rolling" on the search of the right sound mixture....


but I confess...... I am always looking at the pictures of Papas Amps at 6moons like a junkie....on the search of hidden riddles and treasures....I confess...
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Last edited by generg; 26th March 2012 at 07:58 PM.
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Old 26th March 2012, 08:00 PM   #826
generg is offline generg  Germany
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Originally Posted by Tea-Bag View Post
Well then, how does it sound to R100 only amp?
I try to accustom myself to to the sound.....
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Old 27th March 2012, 10:43 AM   #827
protos is offline protos  Greece
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Originally Posted by Michael Rothacher View Post
Yes, the 47K. I've seen SITs with 100uA or more gate leakage current. With 100uA, you'd be dropping 4.7V across a 47K resistor. It's worth a look anyway. Being aware of it is half the solution.
I did check with some and yes the one with 11.5 vgs had a high leakage that accelerated once the sit reached a certain temp. With a 12k there was almost none.However the variation, testing with the 12 k now, is still very wide as I described so no real change there although it seems now the two sits with the highest vgs are more closely matched now with the 12 k. So out of 8 sits I have about three pairs that seem reasonably matched.
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Old 27th March 2012, 10:58 AM   #828
DUC985 is offline DUC985  Germany
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if i look into all current sources, i would like to understand how the voltage drop within mosfet is calculated ? In the latest example we have the R100 at the drain 35V and at the SK82 19V and want around 1.6 current flowing.
So whats the math behind all that ..
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Old 27th March 2012, 11:53 AM   #829
Michael Rothacher is offline Michael Rothacher  United States
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L'Amp: A simple SIT Amp
Good work, protos.

It's very temperature dependent, so you may find things will behave a little better still once they're gooped-up and bolted to a big heatsink. You'll have to use the negative bias supply version to generate the correct bias voltage. You could also do as Generg does and use a battery and pot for testing. You just have to be careful the battery doesn't drain and cause a meltdown.
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Old 27th March 2012, 04:11 PM   #830
Skorpio is offline Skorpio  Denmark
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Quote:
Originally Posted by Zen Mod View Post
convenient place for mucho PSU caps (and possibly just few output ones) - sounds logicall ?

2 reasons for that - poor PSRR of circuit itself , empty pcb if you leave just resistors there

edited - few important words swallowed , probably .... usual ZM's brainfart
One of the power resistors might be PSU series R...
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