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Old 16th January 2010, 08:48 PM   #6661
EUVL is offline EUVL  Europe
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> That's one. I can think of a couple others...

Let me make a fool of myself :

Connect the source of Q1 & Q2 on each (left or right) half together, then connect these two junctions across the two halves with a 10R resistor. The feedback resistors are then 25R and goes from output to the source junction. Non-inverting then.

According to John Curl, this "H" diff pair has very good distortion cancellation.


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Old 16th January 2010, 09:58 PM   #6662
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Hello
Please try to use GR type .
Greets.
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Old 16th January 2010, 10:23 PM   #6663
Zen Mod is offline Zen Mod  Serbia
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Quote:
Originally Posted by EUVL View Post
> ......
Let me make a fool of myself :

.......
No , Patrick - that's my job usually ......

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Old 16th January 2010, 11:22 PM   #6664
Blues is offline Blues  United States
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Quote:
Originally Posted by umut1001 View Post
I do not have low idss jfet.All of them are above 8ma.Does not them work well ?
They will work very well, but are "over qualified". Keep in mind 2SJ074s are very hard to find nowadays. The F5 has P & N ch jfets at the input so high Idss jfets are not necessary.

GR and lowish BL jfets will work very well too.

I am matching BL jfets and will soon make some available to diyers. Some appear to be in the 6 to 7mA range.
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Old 17th January 2010, 09:31 AM   #6665
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Quote:
Originally Posted by wensan View Post
Oh! I am wrong.
Most of signal will be amplified without feedback control.
Thx Wen-san, i understand my mistake now.
It seems there is no way to keep the 2 ways NFB with a symetrical input.
It has to be as follows. But nothing new then.
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Old 17th January 2010, 09:32 AM   #6666
generg is offline generg  Germany
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Would be great to have a solution!
I dont´t want to double all components only to test balanced driving.
I was also looking about an hour over the different possibilities, but I am not experienced enough. No clear result.
Thank you bobodioulasso for trying to get the answer!
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Old 17th January 2010, 09:42 AM   #6667
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Quote:
I dont´t want to double all components only to test balanced driving
Neither to have a lot more dissipation.
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Old 17th January 2010, 09:48 AM   #6668
generg is offline generg  Germany
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Exactly!
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Old 17th January 2010, 04:04 PM   #6669
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So its Showtime for my F5!

I got it hooked up via a 100watt lamp and all seems fine. All the voltages are present, and everything is stable.
I do however measure like 8mV on r12 and r 11 for the bias.
After turning the potmeters for quite some time I suspect something is wrong.

I meseured r3 and r4 and they give about 8 ohms.

Is it possible that I have to turn quite some more (slow pots?)
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Old 17th January 2010, 04:18 PM   #6670
tinitus is offline tinitus  Europe
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Rikkert, be certain that you measure correctly
Does amp get hot or not ?
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