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F5 Turbo Builders Thread
F5 Turbo Builders Thread
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Old Yesterday, 10:46 AM   #6361
nikwatt is offline nikwatt
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F5 v_1
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Old Yesterday, 10:53 AM   #6362
nikwatt is offline nikwatt
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Default scheme f5_V1

scheme v1 from guide
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Old Yesterday, 01:27 PM   #6363
cubicincher is offline cubicincher  Germany
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Default to nikwatt #6360

Hello Nicola,


you use a 600 VA toroid with secondaries of 2x25V~.


After the bridgerectifier and capbank you will 'land' anywhere around +-32,5 V?
(25 V ~ x 1,3 = 32,5V - rule of thumb/ could be a bit higher?).


The voltage rating at 35V of your caps (15000uF / 35V) seems a bit low for me.
Not a lot of headroom! In other words - close to none. I would have used 50V
types minmum to have a safety margin.


Greets
Dirk
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Old Yesterday, 08:00 PM   #6364
nikwatt is offline nikwatt
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Ok....I have other caps
Kermet 15000 40v
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Old Today, 05:45 AM   #6365
verticalmammal is offline verticalmammal  United States
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When I'm using the cascode voltage formula to determine desired resistance values for R25-28, what cascode voltage am I actually shooting for in my F5Tv2 build? Maybe shooting for just under 24V? Using the lowest suggested value of 4.75 across the board I get 16V of cascode voltage. Is that where I want to be or should I look at possibly dropping the resistance of R25,26? Or perhaps I'm misunderstanding something?

Thanks again!
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Old Today, 01:24 PM   #6366
Bfpca is offline Bfpca  Canada
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F5 Turbo Builders Thread
Most people seem to aim at between 11 and 16 volts. I donít think it is super critical. You are lowering the voltage on the input Jfets to a safe level and also reducing the power consumption, so the jfets run cooler.
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Old Today, 02:43 PM   #6367
6L6 is offline 6L6  United States
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F5 Turbo Builders Thread
Just make the cascode resistors all the same so your cascode voltage is approx 1/2 the rails.
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Old Today, 04:26 PM   #6368
verticalmammal is offline verticalmammal  United States
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Quote:
Originally Posted by Bfpca View Post
Most people seem to aim at between 11 and 16 volts. I donít think it is super critical. You are lowering the voltage on the input Jfets to a safe level and also reducing the power consumption, so the jfets run cooler.
Quote:
Originally Posted by 6L6 View Post
Just make the cascode resistors all the same so your cascode voltage is approx 1/2 the rails.
4.75 across the board for 16V on the nose it is then.

Are y'all sick of hearing me say "thanks again" yet? I hope not, I still have a few more parts to source before I start building

Seriously, I hugely appreciate your help.
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Old Today, 07:18 PM   #6369
AudioSan is offline AudioSan  Norway
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16V is a nice place to lande. I don't agree with some others that the voltage is not important. Well, the voltage alone is not. But combined with the current they draw, it makes up the power dissipation. And thats the important factor. Keep it way below the limit.
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