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Old 5th June 2009, 11:26 AM   #3891
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Right! It must 80 not 40!
Then it's better to use normal way...
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Old 5th June 2009, 11:27 AM   #3892
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maybe I can't multiply. I thought my mental arithmetic came to 80off.
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Old 5th June 2009, 11:29 AM   #3893
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No, you were right..
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Old 5th June 2009, 12:01 PM   #3894
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Fore a small AB amp I could do what you suggest, using small caps

Fore classA I would use nothing but big caps, they are tougher

As Andrew explains, too small caps can get pretty hot, if overloaded, and wont last long
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Old 5th June 2009, 12:33 PM   #3895
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Quote:
Originally posted by tinitus
Fore classA I would use nothing but big caps, they are tougher

As Andrew explains, too small caps can get pretty hot, if overloaded, and wont last long
I don't agree.
small caps usually have small ripple capacity.
paralleling small caps to equal the capacity of one large cap usually results in more ripple capacity. It thus reduces the risk of overheating and thus increases the life of the capacitors, provided the caps have cool air circulating around them.
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Old 5th June 2009, 12:36 PM   #3896
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sure
But the question is what is small and what is big
And how many are many

In my book, 22.000uf just starts to get big
And anything below 10.000uf is small
10.000uf I consider neither small nor big
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Old 5th June 2009, 12:51 PM   #3897
AndrewT is online now AndrewT  Scotland
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Hi,
small and large don't affect the conclusion you drew.

Many parallel capacitors have a higher ripple capacity than a single capacitor of the same capacity and similar quality. It matters not whether we are looking at pF or nF or uF or mF.

You said
Quote:
As Andrew explains, too small caps can get pretty hot, if overloaded, and wont last long
I did not say that.
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Old 5th June 2009, 01:16 PM   #3898
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Quote:
Originally posted by AndrewT
I don't agree.
small caps usually have small ripple capacity.
paralleling small caps to equal the capacity of one large cap usually results in more ripple capacity. It thus reduces the risk of overheating and thus increases the life of the capacitors, provided the caps have cool air circulating around them.

Maybe my english isnt that good
But thats what it meant to me
I may simplify a bit too much
Sorry if I dont understand what you say
Or "quoted" you poorly

btw, do you know "FTcap"
Just saw them on BMM site
Up to 220.000uf in 40V

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Old 5th June 2009, 01:26 PM   #3899
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For each channel i use four 12000uf audio grade Elna (made in Thaïland) which do the job very well. I must say that bias is set at 1 amp.
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Old 5th June 2009, 01:28 PM   #3900
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Hi Ozgur,

To choose the right filter capacitance, we should know what is our DC load current and what should be our target ripple voltage. We are however lucky because Papa has done all these for us in his F5 design.

If you want to apply the same bias current of total 2.6A for both channels, try to keep the CRC filter values of the same as the original. It doesn't matter capacitances are pralleled or not as long as the total capacitance is the same. Meanwhile, if you want to reduce the bias current or increase it, you could change CRC values linearly according to the change-rate of the bias.

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